Middle-aged couple in bed discussing erectile dysfunction

Erectile Dysfunction

Erectile Dysfunction

Last Section Update: 10/2012

Contributor(s): Shayna Sandhaus, PhD

1 Overview

Summary and Quick Facts for Erectile Dysfunction

  • Erectile dysfunction is the inability to achieve or sustain a penile erection sufficient for satisfactory male sexual performance. The condition affects up to 30 million American men, and is typically age dependent.
  • This protocol describes the biology of penile erection and highlights the link between cardiovascular disease and sexual function in men. Medications to temporarily improve erectile function will be discussed, as will integrative strategies for reducing cardiovascular risk and improving overall male sexual function through healthy lifestyle choices, pharmaceutical drugs and the use of scientifically studied natural compounds.
  • Medications used to treat erectile dysfunction, such as sildenafil (Viagra®), vardenafil (Levitra®), and tadalafil (Cialis®), improve erectile function by inhibiting the PDE5 enzyme, allowing an erection to persist. Natural interventions such as Kaempferia parviflora and L-arginine may also improve erectile function and male sexual health.

What is Erectile Dysfunction?

Erectile dysfunction (ED) is the inability to achieve or sustain a penile erection for satisfactory sexual performance. ED can cause emotional distress by negatively impacting intimate relationships, self-esteem, and quality of life.

Maintaining an erection requires coordination between multiple body systems, therefore dysfunction can be caused by several factors: cardiovascular disease, decline in hormone levels, diabetes, and some medications, as well as psychological disorders like depression, can all contribute to ED.

Natural interventions such as Kaempferia parviflora and L-arginine may improve erectile function and male sexual health.

What are the Causes and Risk Factors for Erectile Dysfunction?

  • Cardiovascular disease
    • Men with ED should discuss screening for cardiovascular disease with their doctor, as the two conditions are often linked.
  • Hormonal imbalance
    • Low testosterone is often associated with ED. Men with ED should consider having a blood test for total and free testosterone.
  • Aging
  • Hypertension
  • Obesity
  • Diabetes
  • Sedentary lifestyle
  • Psychological factors (eg, depression, anxiety, stress, low self-esteem, and others)

What are Conventional Medical Treatments for Erectile Dysfunction?

  • Phosphodiesterase-5 (PDE-5) inhibitors such as sildenafil (Viagra), vardenafil (Levitra), and tadalafil (Cialis)
  • Intracavernosal medications (delivered via self-injection into the penis)
  • Vacuum erection devices
  • Behavioral interventions (eg, group psychotherapy)
  • Shock wave therapy
  • Hormone therapy (testosterone and/or DHEA)

What Dietary and Lifestyle Changes Can Be Beneficial for Erectile Dysfunction?

  • Exercise regularly
  • Maintain a healthy body weight
  • Eat a diet rich in antioxidants (eg, Mediterranean diet)

What Natural Interventions May Be Beneficial for Erectile Dysfunction?

  • Kaempferia parviflora. This plant is a member of the ginger family traditionally used for improving male sexual health. Multiple clinical studies have established that Kaempferia can improve erectile function, erectile response time, penile size, and intercourse satisfaction.
  • L-arginine. L-arginine is an essential amino acid that plays a significant role in erectile function by helping form nitric oxide, a vasodilator. Supplementation with L-arginine has been shown to restore erectile quality and increase sexual satisfaction. L-arginine, in combination with Pycnogenol, has also been shown to improve male sexual function.
  • Epimedium. Epimedium is a genus of plants that includes over 50 distinct species, colloquially referred to as “horny goat weed.” Icariin, a component derived from one of the plants, improves erectile and sexual function when administered orally.
  • Yohimbine. Yohimbine, a compound derived from the bark of the Yohimbe tree, has been used to treat erectile dysfunction for over 70 years. Clinical studies of yohimbine, alone or in combination with L-arginine, have shown improved erectile function.
  • Ginseng. Ginseng, which was first used in ancient China as a treatment for ED, continues to be a popular natural aphrodisiac. Several clinical studies have shown ginseng supplementation improved erectile function and overall sexual satisfaction among men with ED.
  • Maca. Maca is a root vegetable from the mustard family that can stimulate metabolism, help control body weight, increase energy, improve memory, and reduce stress and depression. Clinical studies suggest maca enhances the production of sex hormones and increases libido.
  • Ginkgo biloba. The sexual benefits of ginkgo biloba were discovered serendipitously when male geriatric patients taking it for memory enhancement reported improved erections. Ginkgo biloba contributes to increased blood flow by increasing nitric oxide bioavailability to vascular smooth muscles of the penis.
  • Muira Puama. Muira Puama is an herb used to enhance erectile function and orgasm in aging men. One study reported that over 60% of men who used the supplement saw improvement.
  • Other natural interventions that may improve male sexual health include chrysin, carnitines, vitamin D, B vitamins, and vitamin E.

Note: Adulterated “natural” sexual health products are a serious concern. Several “natural” products have been found to contain illegal drug-like compounds. Be sure to choose high-quality supplements from trusted sources.

2 Introduction

Erectile dysfunction is the inability to achieve or sustain a penile erection sufficient for satisfactory male sexual performance (Heidelbaugh 2010; McVary 2007). The condition affects up to 30 million American men, and is typically age-dependent (Berookhim 2011; Cellerino 2005; Sadeghi-Nejad 2007). Erectile dysfunction can cause substantial emotional distress by negatively impacting intimate relationships, self-esteem, and overall quality of life (Heidelbaugh 2010; Kolodny 2011; Segal 2012).

Several pharmacologic treatments for erectile dysfunction are available (eg, Viagra® and Cialis®), but these medications provide only temporary benefits and may cause minor to severe side effects such as headache, indigestion, visual disturbances, and even blindness (Stroberg 2006; Rashid 2005; Burnett 2011; Wolfe 2005).

The underlying physiology of erectile function is tied very closely to cardiovascular health. Therefore, men who wish to perform at their sexual peak must take steps to optimize their blood vessel health (Gandaglia 2012; Garcia-Cruz 2012; Ewane 2012). Studies show that improving cardiovascular risk factors via healthy lifestyle modifications and pharmacologic treatment can significantly improve male sexual function (Gupta 2011).

This protocol describes the biology of penile erection and highlights the link between cardiovascular disease and sexual function in men. Medications to temporarily improve erectile function will be discussed, as will integrative strategies for reducing cardiovascular risk and improving overall male sexual function through healthy lifestyle choices, pharmaceutical drugs, and the use of scientifically studied natural compounds.

3 Understanding Erection Physiology

An erection is triggered by a complex interplay between the sympathetic and parasympathetic nervous system, with local sensory stimulation of the genital area and/ or central psychogenic stimulation resulting from visual, tactile, auditory, olfactory, and/or imaginative input (Sadeghi-Nejad 2007; Kolodny 2011). The endothelial cells that line the blood vessels of the penis produce vasoactive factors that dilate blood vessels, one of the most important being nitric oxide.

Nitric oxide, by initiating production of another chemical messenger called cyclic guanosine monophosphate (cGMP), triggers a biochemical cascade leading to expansion (vasodilatation) of penile blood vessels and allows for increased blood flow into the corpus cavernosum, the two columns of spongy tissue that run along the top length of the penis (Kolodny 2011; Heidelbaugh 2010; AUA 2012; Sadeghi-Nejad 2007). As the corpus cavernosum fills with blood it stretches, compressing the primary site where blood exits the penis, called the subtunical venules. This compression causes resistance to blood flow out of the penis, producing and maintaining an erection (Sadeghi-Nejad 2007; Kolodny 2011; NIH 1992; Heidelbaugh 2010).

4 Causes Of Erectile Dysfunction

Achieving an erection requires coordination between many body systems, so there are several ways the process can go wrong (Ritchie 2011). The cause of erectile dysfunction can be biological, psychological, or both (Heidelbaugh 2010).
Biological causes of erectile dysfunction include hormonal, vascular, and neurologic disorders (McVary 2007).

  • Cardiovascular disease accounts for up to 80% of erectile dysfunction cases (Paroni 2012). Atherosclerosis, the most common vascular disease, impedes blood flow to the penis (Ginsberg 2010). Cardiovascular disease and high blood pressure contribute to endothelial dysfunction, which is the most common contributing mechanism to erectile dysfunction overall (Kolodny 2011; Sadeghi-Nejad 2007).
  • Age-related decline in hormone levels (eg, testosterone and dehydroepiandrosterone [DHEA]) is associated with erectile dysfunction (Morales 2011; Kolodny 2011; Mackay 2004). (See “Erectile Dysfunction and Hormones”, below.)
  • Diabetes can interfere with penile blood flow and damage nerves in the penis, leading to erectile dysfunction (Ginsberg 2010).
  • Age-related decline in penile elastic fibers also contributes to erectile dysfunction (Sadeghi-Nejad 2007).
  • Medication-induced erectile dysfunction can occur from several drugs including antihistamines, benzodiazepines, tricyclic antidepressants, and others (Heidelbaugh 2010; Fortney 2012).

Psychological causes such as depression, anxiety, stress, low self-esteem, and various other conditions can contribute to erectile dysfunction as well (Ginsberg 2010; NIH 1992). Psychological problems are often to blame for intermittent erectile dysfunction among young men, while older men with erectile dysfunction frequently have a mixture of both psychological and biological causes (Sadeghi-Nejad 2007).

The Link Between Erectile Dysfunction and Cardiovascular Disease

It is important for men suffering from erectile dysfunction to discuss their symptoms with their physician (Hackett 2009). In addition to recommending an effective treatment for the primary complaint of erectile dysfunction, physicians should also screen for cardiovascular disease (CVD) (Nehra 2012; Sadeghi-Nejad 2007; NIH 1992). This is because erectile dysfunction and CVD share similar risk factors, including aging, hypertension, obesity, and a sedentary lifestyle (Hannan 2009; Ewane 2012; Nunes 2012). Furthermore, erectile dysfunction itself has been shown to independently increase the risk of CVD, stroke, and all-cause death (Kolodny 2011; Heidelbaugh 2010).
Since erectile dysfunction often precedes some cardiovascular events by 2-5 years (Nehra 2012), erectile dysfunction is viewed as a potential early warning sign for CVD (Meldrum 2011). Early detection is critical since CVD is a major cause of disability and death (Ewane 2012).
The abbreviation “ED” can help make this issue easy to understand and remember. For instance, “ED” stands not only for “Erectile Dysfunction”, but also “Endothelial Dysfunction”, “Exercise & Diet” (for prevention), and “Early Detection” of risk factors, which can help avoid “Early Death” due to CVD(Jackson 2006).

Erectile Dysfunction and Hormones


Many facets of male sexual function depend upon male hormones (androgens) such as testosterone (Morales 2011). Testosterone helps support the production of nitric oxide (Kolodny 2011), but also helps maintain libido (Morales 2011). As men age their androgen levels decline. Low androgen levels are observed in as many as one-third of men with erectile dysfunction (Burnett 2011).

Androgen deficiency can directly contribute to erectile dysfunction by negatively impacting penile blood flow and increasing breakdown of cGMP (Martin 2012; Heidelbaugh 2010). Low testosterone is the most common reason for failure to respond to Phosphodiesterase-5 (PDE5) inhibitors (eg, Viagra® and Cialis®), which are drugs that slow the breakdown of cGMP (Hackett 2012).

Clinical guidelines recommend hormone level testing for aging men who suffer from sexual dysfunction. Maintaining optimal testosterone levels is not only important for sexual function, but also for cardiovascular health (Cattabiani 2012). Moreover, low androgen levels are associated with depression, osteoporosis, insulin resistance, increased fat mass, decreased lean body mass, and cognitive dysfunction (Morales 2011; Kolodny 2011). Life Extension recommends that ageing men target optimal free testosterone blood levels of 15 – 25 pg/mL and total testosterone levels of 600 – 900 ng/dL.

Testosterone restoration can lead to improved erectile function and libido in men with low androgen levels (Heidelbaugh 2010). In fact, when PDE5 inhibitors fail, the addition of testosterone therapy is associated with substantial improvement in erectile function among men with low testosterone and may eliminate the need for PDE5 inhibitors altogether (Heidelbaugh 2010; Kolodny 2011; Morales 2011; Hackett 2012). Refer to Life Extension’s Male Hormone Restoration protocol for more information.


Dehydroepiandrosterone (DHEA) is a precursor to testosterone (Oloyo 2011; Maggi 2012). As with testosterone, aging is associated with decreased levels of DHEA. Circulating levels of DHEA can decline by up to 80% from age 25 to 80 (Maggi 2012). Low DHEA levels have been linked to erectile dysfunction (Mackay 2004; Feldman 1994). Studies have shown that oral DHEA supplementation may improve sexual performance, as measured by erectile function, orgasmic function, sexual desire, intercourse satisfaction, and overall satisfaction in some men (Reiter 1999; Reiter 2001). Life Extension recommends an optimal target blood level for DHEA-sulfate of 350 – 490 µg/dL.

Aromatase Inhibitors, Testosterone Restoration, and Testosterone/ Estrogen Balance

Physicians versed in male hormone restoration know that exogenous administration of testosterone may increase estrogen (estradiol) levels in aging men, in particular aging men with significant amounts of visceral fat. The conversion of testosterone into estrogen is called aromatization and is mediated by an enzyme called aromatase (Traish 2007). Aromatase inhibitors (eg, anastrozole [Arimidex®]) are drugs that inhibit the activity of the aromatase enzyme, thereby reducing the amount of testosterone converted into estradiol.

When used concurrently with testosterone supplementation, aromatase inhibitors allow testosterone levels to rise without being converted into excess estrogen. Reports suggest that aromatase inhibitor therapy can improve sexual function in men (Traish 2007).

Maintaining healthy testosterone/estrogen balance has other important implications for aging males. For example, in a study among men with heart failure, both low and high estradiol levels were associated with significantly increased chances of death compared to “balanced” levels (Jankowska 2009). More about estrogen/testosterone balance in men is available in the Life Extension Magazine article entitled “Why Estrogen Balance is Critical to Aging Men”.
Life Extension suggests an optimal estrogen level (measured as estradiol) of 20 – 40 pg/mL for men.

5 Conventional Treatment Of Erectile Dysfunction

Phosphodiesterase-5 (PDE5) Inhibitors

The signaling molecule cyclic guanosine monophosphate (cGMP) is an important mediator of vasodilatation, penile blood flow, and therefore erection. The natural destruction of cGMP by the phosphodiesterase-5 (PDE5) enzyme effectively shuts down the erection process, returning the penis to its non-erect (flaccid) state (Kolodny 2011).
Medications used to treat erectile dysfunction, such as sildenafil (Viagra®), vardenafil (Levitra®), and tadalafil (Cialis®), improve erectile function by inhibiting the PDE5 enzyme, allowing an erection to persist (Kolodny 2011). However, approximately one-third of men with erectile dysfunction do not respond to PDE5 inhibitors (Heidelbaugh 2010). Men whose erectile dysfunction is not improved by PDE5 inhibitors may have low testosterone levels and should have a testosterone blood test (Nehra 2012). 

Although PDE5 inhibitors are generally well tolerated, they can cause a number of side effects including headache, indigestion, visual disturbances, priapism (ie, painful, prolonged erection lasting more than 6 hours), and even blindness (Stroberg 2006; Rashid 2005; Burnett 2011; Wolfe 2005). Furthermore, the use of PDE5 inhibitors is limited in some men by contraindications such as cardiovascular disease. These drugs can also interact with other medications (eg, nitrates) and cause negative reactions (Rashid 2005; Burnett 2011; Wolfe 2005; Heidelbaugh 2010). PDE5 inhibitors only improve erectile function, not overall sexual function (Heidelbaugh 2010).

Intracavernosal Medications

In men who are not good candidates for or do not respond well to PDE5 inhibitors, intracavernosal vasodilating medications are a second-line treatment option. These treatments are delivered via self-injection into the cavernosum. Adverse effects may include pain, prolonged erection, and fibrosis (MD Consult 2009a,b;  MD Consult 2010).

  • Alprostadil. Alprostadil is synthetic prostaglandin E1, which is a biochemical signaling molecule with vasodilatory properties (Lea 1996; Costabile 2008). Studies show alprostadil to be effective in about 70% of men with erectile dysfunction (Lea 1996). Alprostadil can now be delivered via topical cream as well, which has demonstrated a success rate similar to injectable forms (Rooney 2009; MD Consult 2012a).
  • Papaverine. Papaverine, a compound derived from the poppy plant, nonspecifically inhibits phosphodiesterase enzymes and modulates calcium signaling. It does not possess opiate properties like some other poppy derivatives such as morphine. Studies suggest a patient satisfaction rate of about 44%. Papaverine use may increase liver function tests with the potential for hepatotoxicity (Pinsky 2010).
  • Phentolamine. Phentolamine blocks alpha-1 and -2 adrenergic receptors. This helps facilitate erection by impairing muscle constriction. Phentolamine alone is not sufficient to trigger and sustain rigid erection, so it is used in combination with other intracavernosal agents for an additive effect. Because phentolamine is expensive and needs to be refrigerated, it may be less convenient (Pinsky 2010).

Vacuum Erection Devices (VEDs)

Another alternative is utilizing a vacuum device to artificially increase penile blood flow. These devices consist of plastic cylinders that are placed over the penis and vacuumed by a pump to negative pressure to allow cavernosal expansion and erection. Constriction rings are then placed at the base of the penis to retain blood. Vacuum erection devices provide a relatively safe and efficacious alternative for those unresponsive to or unable to take oral medications. Disadvantages include lack of penile stability, which may interfere with sexual performance, and inhibited ejaculation (Pinsky 2010).

Behavioral Interventions

Erectile function and overall sexual satisfaction can be considerably impacted by psychological and interpersonal factors. Evidence suggests a psychogenic contribution to as many as 40% of erectile dysfunction cases. Psychosocial variables such as anxiety about seeking erectile dysfunction treatment undermine availability of effective treatment options as well. A comprehensive review conducted in 2008 showed that group psychotherapy can significantly improve erectile dysfunction and complement pharmacologic treatment strategies (Melnik 2008).

Shock Wave Therapy

Extracorporeal ultrasound shock wave therapy is used to treat some penile disorders such as Peyronie’s disease (Palmieri 2012; MD Consult 2012b).  Application of low-intensity ultrasound shock waves to the penis is emerging as a treatment for erectile dysfunction among men without other penile disorders. In a pioneering, randomized, double-blind, sham-controlled study on 67 men, researchers showed that shock wave therapy significantly improved erectile function and penile blood flow among previous responders to PDE-5 inhibitors. Treatment was well tolerated with none of the subjects reporting discomfort or adverse events (Vardi 2012). Another study showed that shock wave therapy improved erectile function in 29 men who responded poorly to PDE5 inhibitors (Gruenwald 2012).

6 Lifestyle And Erectile Dysfunction

Certain modifiable conditions and behaviors increase the chances of developing erectile dysfunction. These include lack of physical activity and obesity, as well as alcohol, tobacco, and illicit drug use (Sadeghi-Nejad 2007; Fortney 2012; Meldrum 2011). Eating an unhealthy diet low in antioxidants is also linked to erectile dysfunction (Meldrum 2011; Ledda 2010).
The following lifestyle modifications may improve erectile function (Heidelbaugh 2010):

  1. Regular physical exercise: Studies have shown that exercise can improve erectile function, sexual response, and overall cardiovascular health (Meldrum 2011; La Vignera 2012).
  2. Weight control and diet: Obesity nearly doubles the risk of erectile dysfunction (Heidelbaugh 2010). Weight control and adoption of a healthier diet (such the Mediterranean diet) may reduce this risk. The principles of a Mediterranean diet include high intake of fruits, vegetables, nuts, whole grains, and fish, with low intake of refined grains as well as red and processed meats. In combination with physical activity, a Mediterranean diet may be especially beneficial for men with erectile dysfunction who also have metabolic syndrome or diabetes (Meldrum 2011; La Vignera 2012; Esposito 2006,2010; Giugliano 2010). Furthermore, diets rich in antioxidants have been shown to improve penile blood flow, erectile activity, smooth muscle relaxation, and fibrosis (Meldrum 2011; Zhang 2011).

7 Nutrients

A variety of natural modalities may improve erectile function and male sexual health (Ho 2011; Chung 2011; Burnett 2011; de Andrade 2007).

Kaempferia parviflora - Kaempferia parviflora, a member of the ginger family, is a plant native to Southeast Asia. It has traditionally been used for male sexual health (Saokaew 2016), and emerging clinical research has established that Kaempferia can enhance erectile function, erectile response time, penile size, and intercourse satisfaction (Stein 2018; Wannanon 2012). Kaempferia extracts contain 5,7-dimethoxyflavone, a compound shown in laboratory studies to inhibit phosphodiesterase-5 activity—the same mechanism as leading erectile dysfunction medications—and to enhance vasorelaxation (Temkitthawon 2011; Tep-Areenan 2010). Kaempferia extract appears also to activate central nervous system pathways involved in sexual responsiveness (Wattanathorn 2012). These clinical findings confirm evidence from animal models in which Kaempferia improved sexual and copulation behavior (Wattanathorn 2012; Chaturapanich 2008; Chaturapanich 2012).

In a 30-day open-label clinical study, 13 generally healthy men aged 50‒68 with self-reported mild erectile dysfunction received 100 mg of a Kaempferia extract standardized to a 5% content of 5,7-dimethoxyflavone. At the end of the trial, the men reported significant improvements in erectile function and intercourse satisfaction, as well as in total scores on a standardized inventory of erectile function. The Kaempferia extract was found to be safe and well-tolerated (Stein 2018).

In a randomized, placebo-controlled trial, 45 men of an average age of 65 received 25 or 90 mg of Kaempferia extract, once daily, for 60 days. Although the authors concluded that the 25 mg dosage likely was insufficient to reach therapeutic levels, men receiving 90 mg were able, at the 30- and 60-day evaluation, to achieve a full erection in roughly half the time of those receiving placebo. Men in the 90 mg group also experienced an increase in size of roughly ½ inch in length and circumference in both flaccid and erect states, compared with baseline (Wannanon 2012).

L-arginine – L-arginine is an essential amino acid with numerous metabolic actions (NIH 2012; Gentile 2009). It plays a significant role in erectile function by contributing to the formation of the vasodilator nitric oxide (Paroni 2012; Mathers 2009; Masuda 2008; Nunes 2011).

Supplementation with L-arginine has been shown to restore erectile quality and increase sexual satisfaction by boosting nitric oxide bioactivity and improving penile blood flow (Cormio 2011; Aoki 2012; Ledda 2010; Giles 2006). The efficacy of L-arginine, combined with Pycnogenol®, a bioactive compound derived from French maritime pine bark with vasodilatory properties, has been tested in 5 independent clinical studies and been shown to improve male sexual function (Stanislavov 2003,2008,2009; EBDR 2005; Nikolova 2007). This combination is called Prelox®. The first clinical trial to report successful treatment of erectile dysfunction with Pycnogenol® and L-arginine aspartate involved 40 men between 25 and 45 years of age suffering from mild erectile dysfunction. A regimen of  80 mg of Pycnogenol® and 1.7 grams of L- arginine daily yielded significant improvement, with 32 patients (80%) enjoying normal erections. L-arginine, together with an increased amount of Pycnogenol® (120 mg per day), further increased the number of patients with restored normal erectile function. At the end of the three month trial, 37 patients, equivalent to 92.5% of all participants, achieved normal erectile function (Stanislavov 2003).
L-arginine supplementation has also been shown to attenuate endothelial dysfunction associated with high cholesterol and coronary heart disease (Gianfrilli 2012). Since endothelial dysfunction diminishes the effects of PDE-5 inhibitors, L-arginine supplementation may be a useful add-on therapy for men who do not respond to these drugs (Gianfrilli 2012; Porst 2010; Gentile 2009).

Epimedium Epimedium is a genus of over 50 distinct species of plants. It is colloquially referred to as horny goat weed because it was observed that goats who ate it subsequently engaged in intense sexual activity. Epimedium has been used in traditional Chinese medicine for centuries as a natural aphrodisiac and for the treatment of erectile dysfunction (Ma 2011; Metz 2009; Shindel 2010).

Research has shown that icariin, a bioactive component derived from the aerial portion of the Epimedium plant, improves erectile and sexual function when administered orally (Xin 2003; Shindel 2010). Laboratory data show that icariin can inhibit PDE5, improve penile blood flow, and support endothelial integrity. Icariin also has testosterone-like properties and is associated with increased intracavernosal pressure and nitric oxide levels (Shindel 2010; Liu 2005,2011; Zhang 2012; Metz 2009).

Yohimbine – Yohimbine, a compound derived from the bark of the Yohimbe tree, has been utilized in the treatment of erectile dysfunction for over 70 years (Tamler 2007). Yohimbine’s mechanism of action is thought to be its ability to enhance smooth muscle relaxation, thereby promoting penile erection. It is thought to accomplish this by blocking the effects of neurotransmitter receptors called alpha-2 adrenergic receptors, which promote smooth muscle contraction when activated (Traish 2000).
Clinical studies of yohimbine, alone or in combination with L-arginine, have shown improved erectile function (Kernohan 2005; Dinsmore 2005; Ho 2011). In one clinical trial, yohimbine was effective for up to 84% of male volunteers, depending on the type of erectile dysfunction (Pushkar 2002). Compared to placebo, yohimbine was more effective at improving self-reported sexual function and penile rigidity (Tharyan 2006; Ernst 1998). Another study found that yohimbine improved erectile function in 42% of men with erectile dysfunction, compared to 27% of subjects taking placebo (Morales 1987). Additionally, yohimbine may be particularly effective among type 2 diabetics and those with non-biological causes of erectile dysfunction (Tamler 2007; Tanweer 2010).

Yohimbine may cause some side effects including heart palpitations, anxiety, fine tremor, and high blood pressure. These occur infrequently and are usually reversible (Tamler 2007; Tharyan 2006; Ernst 2011).

Ginseng – Ginseng belongs to the genus Panax, which is a group of slow-growing perennial plants with distinctively fleshy roots (Shamloul 2010). Five thousand years after it was first used for the treatment of erectile dysfunction in ancient China, ginseng continues to be a popular natural aphrodisiac (Nair 2012). An estimated 6 million Americans have used ginseng for the improvement of sexual dysfunction (de Andrade 2007; Chan 2012).

Ginsenosides, the principle active constituents in ginseng, have cardio-protective, immune-stimulatory, anti-fatigue, hepato-protective, and antioxidant effects. In addition, they also increase the synthesis of nitric oxide (Kim 2009). In animal studies, ginsenosides have been shown to relax penile smooth muscle tissue (through the release of nitric oxide) and potentially affect chemical pathways involving cGMP and testosterone (Jang 2008; Wang 2010).

A 2009 clinical study showed that 1000 mg of Panax ginseng twice daily improved erectile function and overall sexual satisfaction among men with erectile dysfunction. The study also found that ginseng potentially increased testosterone levels. The authors concluded that ginseng could be effective for improving erectile function regardless of age and severity of dysfunction (Kim 2009). Another study showed that ginseng significantly improved penile rigidity, libido, and satisfaction among men with erectile dysfunction (de Andrade 2007).

Maca – Maca (Lepidium meyenii) is a root vegetable belonging to the mustard (ie, Brassica) family (Zenico 2009; MacKay 2004). Ancient Peruvians have cultivated maca for millennia and taken advantage of its aphrodisiac properties (Hudson 2008; MacKay 2004). The dried root of the maca plant is a rich source of amino acids, iodine, iron, and magnesium (Zenico 2009; Shin 2010). 

Scientific studies support the aphrodisiac activity of maca, and show that it stimulates metabolism, helps control body weight, increases energy, improves memory, and reduces stress and depression (Zheng 2000; Hudson 2008). It also shows androgen-like effects in animals (Shin 2010). Human clinical studies suggest that maca enhances the production of sex hormones, increases libido, and improves well-being (Hudson 2008; Shin 2010; Zenico 2009; Gonzales 2002). The aphrodisiac activity of maca may be due to local effects on erectile function and/or central nervous system effects (Zenico 2009).

Ginkgo biloba – Extracts of leaves from the Ginkgo biloba tree have been used for centuries in the treatment of asthma, fatigue, circulatory problems, and vertigo (Cybulska-Heinrich 2012). It has more recently been associated with enhanced sexual desire, excitement, orgasm, and resolution, as well as neuroprotective properties (Moyad 2002; Cybulska-Heinrich 2012). The sexual benefits of ginkgo were discovered serendipitously when male geriatric patients taking Ginkgo biloba for memory enhancement reported improved erections (MacKay 2004).

In addition to experimental data showing that Ginkgo biloba can enhance sexual behavior in rats (Yeh 2008), clinical studies have revealed it can increase penile blood supply and improve erectile function in humans (Moyad 2002). Ginkgo contributes to increased blood flow by increasing nitric oxide bioavailability to vascular smooth muscles of the penis (MacKay 2004; Rowland 2003). In one study, 120-240 mg of Ginkgo biloba extract was associated with a 76% improvement in sexual dysfunction among men being treated with antidepressants (Cohen 1998).

Muira Puama - Muira Puama, also known as potency wood, is an herb that comes from a small bush in the rain forests of Brazil. It has been associated with enhanced erectile function and orgasm in aging men suffering the effects of fatigue or age-related complaints. In one study of 262 men suffering from poor sexual desire, more than 60% reported improvements with Muira Puama supplementation. In addition, more than half of the men with erectile dysfunction reported that Muira Puama was beneficial. While Muira Puama’s mechanism of action remains unknown, its actions may be related to its plant sterol content. Plant sterols may contribute to increased synthesis of testosterone (Rowland 2003).

Chrysin: The bioflavonoid chrysin is a natural aromatase inhibitor that helps minimize the conversion of testosterone to estrogen (Kellis 1984). Although chrysin has low oral bioavailability (Walle 2001), its bioavailability may be improved by co-administration with the black pepper extract piperine, thus enhancing its actions as an aromatase inhibitor (Srinivasan 2007).
Carnitines – Carnitine (including acetyl-L-carnitine [ALC] and propionyl-L-carnitine [PLC]) are natural amino acid compounds. Studies have linked carnitines to a variety of positive effects among men with low testosterone, including improved erection quality/function, orgasm, and general sexual well-being (Gianfrilli 2012; Malaguarnera 2012). Carnitines may have testosterone-like effects in the body (Cavallini 2004). A 2012 study showed that 250 mg of PLC daily for 3 months (in combination with 2500 mg of L-arginine and 20 mg of niacin) successfully improved erections in 40% of men with erectile dysfunction, while nearly 77% of men reported a partial response (Gianfrilli 2012).

Carnitines may improve endothelial function by acting as antioxidants in these cells (Ginafrilli 2012). For this reason, carnitine supplementation may be generally beneficial for cardiovascular health (Malaguarnera 2012; Mingorance 2011). Carnitine may also have a place as a combination therapy with PDE5 inhibitors, especially among patients whose erectile dysfunction is caused by underlying endothelial disorders, such as diabetes (Gentile 2004).

Vitamin D – Vitamin D insufficiency (as defined by serum levels <30 ng/mL) affects over 75% of the United States population. Vitamin D deficiency may be a risk factor for erectile dysfunction, since it contributes to arterial stiffness and vascular dysfunction. In a 2012 paper, researchers theorized that optimizing vitamin D levels could reduce certain risk factors for erectile dysfunction, such as arterial stiffness, diabetes mellitus, hypertension, and inflammation of the endothelium. Vitamin D has also been shown to stimulate the production of nitric oxide (Sorenson 2012).

B vitamins – Inadequate intake of B vitamins, especially folate, B6, and B12, can contribute to elevated levels of homocysteine. Homocysteine is a metabolic amino acid derivative that can damage endothelial cells and contribute to cardiovascular disease (Wang 2011; Lombardo 2010). In one study, homocysteine impaired carvernosal smooth muscle relaxation. The authors proposed homocysteine as a risk factor for erectile dysfunction (Khan 1999). B vitamin supplementation can help keep homocysteine levels in a healthy range; therefore, may mitigate erectile dysfunction (Wang 2011; Ng 2011; Lombardo 2010). Life Extension recommends homocysteine levels be kept below 8 µmol/L for optimal health.

Vitamin E – Erectile dysfunction is often associated with oxidative stress, which impairs endothelial function and reduces nitric oxide bioavailability (Meldrum 2012; Helmy 2012). Both experimental and clinical data has shown that vitamin E may be beneficial for erectile dysfunction, since it enhances endothelial cell function, scavenges free radicals, improves nitric oxide-mediated relaxation, preserves nerve function, and increases intracavernosal pressure (Helmy 2012; Kondoh 2008). Through these various actions, vitamin E has shown promising results in experimental models of erectile dysfunction caused by aging and hypertension (Helmy 2012; Ushiyama 2008). Vitamin E may also be beneficial when added to PDE5 inhibitor treatment, especially if treatment with a PDE5 inhibitor alone has not been successful in the past (Kondoh 2008).

Adulterated Sexual Health Supplements

A number of unscrupulous marketers have attempted to take advantage of consumers by adulterating “natural” sexual health products with drug analogs (Balayssac 2012; Lee 2011). For instance, a 2011 study identified an illegal Viagra-like compound (mutaprodenafil) in a “male enhancement” product (Demizu 2011). Likewise, a 2012 analysis of 9 supplements intended for enhancing male sexual performance found that only 1 contained a true natural product. The other supplements were found to have untested and unapproved synthetic drug analogs, which may cause significant side effects (Balayssac 2012; Petroczi 2011; Lee 2011). Supplements marketed for boosting testosterone, increasing libido, and/or enhancing male sexual performance are prone to contamination or spiking by profiteers (Petroczi 2011; Csupor 2010).

Insist on purchasing only the highest quality dietary supplements from trusted, research-focused firms.  Choose a brand that uses advanced analytical methods, such as high-performance liquid chromatography, gas chromatography, and mass spectrometry to ensure products meet label claims for potency and purity, and do not contain illegal drug analogs (Lee 2011). Furthermore, be sure to choose a dietary supplement company that tests its raw materials using United States (US) Pharmacopeia and other exacting pharmaceutical assay standards.


  • Oct: Comprehensive update & review

Disclaimer and Safety Information

This information (and any accompanying material) is not intended to replace the attention or advice of a physician or other qualified health care professional. Anyone who wishes to embark on any dietary, drug, exercise, or other lifestyle change intended to prevent or treat a specific disease or condition should first consult with and seek clearance from a physician or other qualified health care professional. Pregnant women in particular should seek the advice of a physician before using any protocol listed on this website. The protocols described on this website are for adults only, unless otherwise specified. Product labels may contain important safety information and the most recent product information provided by the product manufacturers should be carefully reviewed prior to use to verify the dose, administration, and contraindications. National, state, and local laws may vary regarding the use and application of many of the therapies discussed. The reader assumes the risk of any injuries. The authors and publishers, their affiliates and assigns are not liable for any injury and/or damage to persons arising from this protocol and expressly disclaim responsibility for any adverse effects resulting from the use of the information contained herein.

The protocols raise many issues that are subject to change as new data emerge. None of our suggested protocol regimens can guarantee health benefits. Life Extension has not performed independent verification of the data contained in the referenced materials, and expressly disclaims responsibility for any error in the literature.

Aoki H, Nagao J, Ueda T, et al. Clinical assessment of a supplement of Pycnogenol(R) and L-arginine in Japanese patients with mild to moderate erectile dysfunction. Phytother Res. 2012;26(2):204-7.

AUA (American Urological Association) Managing Your Peyronie’s Disease. In: Ferri’s Netter Patient Advisor (pg. 988) Copyright 2012 Saunders, an imprint of Elsevier, Inc.

Balayssac S, Gilard V, Zedde C, Martino R, Malet-Martino M. Analysis of herbal dietary supplements for sexual performance enhancement: first characterization of propoxyphenyl-thiohydroxyhomosildenafil and identification of sildenafil, thiosildenafil, phentolamine and tetrahydropalmatine as adulterants. J Pharm Biomed Anal. 2012;63:135-150.

Berookhim BM, Bar-Chama N. Medical implications of erectile dysfunction. Med Clin North Am. 2011;95(1):213-221.

Burnett A. (2011) Chapter 24: Evaluation and Management of Erectile Dysfunction (pg 721). In: Wein A. (Ed.), Campbell-Walsh Urology (10th ed). Saunders, An Imprint of Elsevier.

Cattabiani C, Basaria S, Ceda GP, Luci M, Vignali A, Lauretani F, . . . Maggio M. Relationship between testosterone deficiency and cardiovascular risk and mortality in adult men. Journal of endocrinological investigation. Jan 2012;35(1):104-120.

Cavallini G, Caracciolo S, Vitali G, Modenini F, Biagiotti G. Carnitine versus androgen administration in the treatment of sexual dysfunction, depressed mood, and fatigue associated with male aging. Urology. 2004;63(4):641-646.

Cellerino A, Jannini EA. Why humans need type 5 phosphodiesterase inhibitors. Int J Androl. 2005;2:14-17.

Chan SW. Panax ginseng, Rhodiolarosea and Schisandrachinensis.Int J Food SciNutr. 2012;1:75-81.

Chaturapanich G, Chaiyakul S, Verawatnapakul V, Pholpramool C. Effects of Kaempferia parviflora extracts on reproductive parameters and spermatic blood flow in male rats. Reproduction (Cambridge, England). Oct 2008;136(4):515-522.

Chaturapanich G, Chaiyakul S, Verawatnapakul V, Yimlamai T, Pholpramool C. Enhancement of aphrodisiac activity in male rats by ethanol extract of Kaempferia parviflora and exercise training. Andrologia. May 2012;44 Suppl 1:323-328.

Chung E, Brock GB. Emerging and novel therapeutic approaches in the treatment of male erectile dysfunction.CurrUrol Rep. 2011;12(6):432-43.

Cohen AJ, Bartlik B. Ginkgo biloba for antidepressant-induced sexual dysfunction. J Sex Marital Ther. 1998;24(2):139-143.

Cormio L, De Siati M, Lorusso F, et al. Oral L-citrulline supplementation improves erection hardness in men with mild erectile dysfunction. Urology. 2011;77(1):119-22.

Costabile RA, Mammen T, Hwang K.An overview and expert opinion on the use of alprostadil in the treatment of sexual dysfunction.Expert opinion on pharmacotherapy. Jun 2008;9(8):1421-1429.

Csupor D, Szekeres A, Kecskemeti A, et al. [Dietary supplements on the domestic market adulterated with sildenafil and tadalafil].OrvHetil. 2010;151(43):1783-1789.

Cybulska-Heinrich AK, Mozaffarieh M, Flammer J. Ginkgo biloba: an adjuvant therapy for progressive normal and high tension glaucoma. Mol Vis. 2012;18:390-402.

de Andrade E, de Mesquita AA, Claro Jde A, et al. Study of the efficacy of Korean Red Ginseng in the treatment of erectile dysfunction. Asian J Androl. 2007;9(2):241-244.

Demizu Y, Wakana D, Kamakura H, Kurihara M, Okuda H, Goda Y. Identification of mutaprodenafil in a dietary supplement and its subsequent synthesis. Chem Pharm Bull. 2011;59(10):1314-1316.

Dinsmore WW. Available and future treatments for erectile dysfunction.Clin Cornerstone. 2005;7(1):37-45.

EBDR (European Bulletin of Drug Research). 2005;13(1): 7–13.

Ernst E, Pittler MH. Yohimbine for erectile dysfunction: a systematic review and meta-analysis of randomized clinical trials. J Urol. 1998;159(2):433-436.

Ernst E, Posadzki P, Lee MS. Complementary and alternative medicine (CAM) for sexual dysfunction and erectile dysfunction in older men and women: an overview of systematic reviews. Maturitas. 2011;70(1):37-41.

Esposito K, Ciotola M, Giugliano F, et al. Mediterranean diet improves erectile function in subjects with the metabolic syndrome. Int J Impot Res. 2006;18(4):405-410.

Esposito K, Giugliano F, Maiorino MI, Giugliano D. Dietary factors, Mediterranean diet and erectile dysfunction. J Sex Med. 2010;7(7):2338-2345.

Ewane KA, Lin HC, Wang R. Should patients with erectile dysfunction be evaluated for cardiovascular disease? Asian J Androl. 2012;14(1):138-144.

Feldman HA, Goldstein I, Hatzichristou DG, Krane RJ, McKinlay JB. Impotence and its medical and psychosocial correlates: results of the Massachusetts Male Aging Study. The Journal of urology. Jan 1994;151(1):54-61.

Fortney L. (2012) Chapter 60: Erectile Dysfunction (pg 560). In: Rakel D. (Ed.), Integrative Medicine (3rd ed). Saunders, An Imprint of Elsevier.

Gandaglia G, Salonia A, Passoni N, Montorsi P, Briganti A, Montorsi F. Erectile dysfunction as a cardiovascular risk factor in patients with diabetes. Endocrine. Sep 5 2012.

Garcia-Cruz E, Piqueras M, Gosalbez D, Perez-Marquez M, Peri L, Izquierdo L, . . . Alcaraz A. [Erectile dysfunction and its severity are related to the number of cardiovascular risk factors]. Actasurologicasespanolas. May 2012;36(5):291-295.

Gentile V, Antonini G, AntonellaBertozzi M, et al. Effect of propionyl-L-carnitine, L-arginine and nicotinic acid on the efficacy of vardenafil in the treatment of erectile dysfunction in diabetes.Curr Med Res Opin. 2009;25(9):2223-8.

Gentile V, Vicini P, Prigiotti G, Koverech A, Di Silverio F. Preliminary observations on the use of propionyl-L-carnitine in combination with sildenafil in patients with erectile dysfunction and diabetes. Curr Med Res Opin. 2004;20(9):1377-1384.

Gianfrilli D, Lauretta R, Di Dato C, et al. Propionyl-L-carnitine, L-arginine and niacin in sexual medicine: a nutraceutical approach to erectile dysfunction. Andrologia. 2012;1:600-604.

Giles TD. Aspects of nitric oxide in health and disease: a focus on hypertension and cardiovascular disease. J ClinHypertens. 2006;8(12 Suppl 4):2-16.

Ginsberg TB. Male sexuality.ClinGeriatr Med. 2010;26(2):185-195.

Giugliano F, Maiorino MI, Bellastella G, et al. Adherence to Mediterranean diet and erectile dysfunction in men with type 2 diabetes. J Sex Med. 2010;7(5):1911-1917.

Gonzales GF, Cordova A, Vega K, et al. Effect of Lepidiummeyenii (MACA) on sexual desire and its absent relationship with serum testosterone levels in adult healthy men. Andrologia. 2002;34(6):367-372.

Gruenwald I, Appel B, Vardi Y. Low-intensity extracorporeal shock wave therapy--a novel effective treatment for erectile dysfunction in severe ED patients who respond poorly to PDE5 inhibitor therapy. The journal of sexual medicine. Jan 2012;9(1):259-264.

Gupta BP, Murad MH, Clifton MM, Prokop L, Nehra A, Kopecky SL. The effect of lifestyle modification and cardiovascular risk factor reduction on erectile dysfunction: a systematic review and meta-analysis. Archives of internal medicine. Nov 14 2011;171(20):1797-1803.

Hackett G. Testosterone measurement - mandatory in ALL men with ED. International Journal of Clinical Practice. 2012;66(1):113-113.

Hackett G. The burden and extent of comorbid conditions in patients with erectile dysfunction.Int J ClinPract. 2009;63(8):1205-1213.

Hannan JL, Maio MT, Komolova M, Adams MA.Beneficial impact of exercise and obesity interventions on erectile function and its risk factors. J Sex Med. 2009;3:254-261.

Heidelbaugh JJ. Management of erectile dysfunction. Am Fam Physician. 2010;81(3):305-312.

Helmy MM, Senbel AM.Evaluation of vitamin E in the treatment of erectile dysfunction in aged rats. Life Sci. 2012;90(13-14):489-494.

Ho CC, Tan HM. Rise of herbal and traditional medicine in erectile dysfunction management.CurrUrol Rep. 2011;12(6):470-478.

Hudson T. Maca: new insights on an ancient plant. Integrative Medicine: A Clinician’s Journal 2008;7(6):54-57.

Jackson G, Rosen RC, Kloner RA, Kostis JB. The second Princeton consensus on sexual dysfunction and cardiac risk: new guidelines for sexual medicine. J Sex Med. 2006;3(1):28-36.

Jang DJ, Lee MS, Shin BC, Lee YC, Ernst E. Red ginseng for treating erectile dysfunction: a systematic review. Br J ClinPharmacol. 2008;66(4):444-450.

Jankowska EA, Rozentryt P, Ponikowska B, Hartmann O, Kustrzycka-Kratochwil D, Reczuch K, . . . Ponikowski P. Circulating estradiol and mortality in men with systolic chronic heart failure. JAMA : the journal of the American Medical Association. May 13 2009;301(18):1892-1901.

Kellis JT, Jr., Vickery LE.Inhibition of human estrogen synthetase (aromatase) by flavones.Science. Sep 7 1984;225(4666):1032-4.

Kernohan AF, McIntyre M, Hughes DM, Tam SW, Worcel M, Reid JL. An oral yohimbine/L-arginine combination (NMI 861) for the treatment of male erectile dysfunction: a pharmacokinetic, pharmacodynamic and interaction study with intravenous nitroglycerine in healthy male subjects. Br J ClinPharmacol. 2005;59(1):85-93.

Khan MA, Thompson CS, Emsley AM, Mumtaz FH, Mikhailidis DP, Angelini GD, . . . Jeremy JY. The interaction of homocysteine and copper markedly inhibits the relaxation of rabbit corpus cavernosum: new risk factors for angiopathic erectile dysfunction? BJU international. Oct 1999;84(6):720-724.

Kim TH, Jeon SH, Hahn EJ, et al. Effects of tissue-cultured mountain ginseng (Panax ginseng CA Meyer) extract on male patients with erectile dysfunction. Asian J Androl. 2009;11(3):356-361.

Kolodny L. (2011) Chapter 17: Men’s Health: Erectile Dysfunction (pg. 971). In: Bope E., Kellerman R. (Eds.), Conn's Current Therapy (1st ed). Saunders, An Imprint of Elsevier.

Kondoh N, Higuchi Y, Maruyama T, Nojima M, Yamamoto S, Shima H. Salvage therapy trial for erectile dysfunction using phosphodiesterase type 5 inhibitors and vitamin E: preliminary report. Aging Male. 2008;11(4):167-170.

La Vignera S, Condorelli R, Vicari E, D'Agata R, Calogero AE. Physical activity and erectile dysfunction in middle-aged men.J Androl. 2012;33(2):154-161.

Lea AP, Bryson HM, Balfour JA.Intracavernousalprostadil.A review of its pharmacodynamic and pharmacokinetic properties and therapeutic potential in erectile dysfunction.Drugs & aging. Jan 1996;8(1):56-74.

Ledda A, Belcaro G, Cesarone MR, Dugall M, Schonlau F. Investigation of a complex plant extract for mild to moderate erectile dysfunction in a randomized, double-blind, placebo-controlled, parallel-arm study. BJU Int. 2010;106(7):1030-3.

Lee HM, Lee BJ. A novel approach to simultaneous screening and confirmation of regulated pharmaceutical compounds in dietary supplements by LC/MS/MS with an information-dependent acquisition method. Food AdditContam Part AChem Anal Control Expo Risk Assess. 2011;28(4):396-407.

Liu T, Xin H, Li WR, et al. Effects of icariin on improving erectile function in streptozotocin-induced diabetic rats. J Sex Med. 2011;8(10):2761-2772.

Liu WJ, Xin ZC, Xin H, Yuan YM, Tian L, Guo YL.Effects of icariin on erectile function and expression of nitric oxide synthase isoforms in castrated rats.Asian J Androl. 2005;7(4):381-388.

Lombardo F, Tsamatropoulos P, Piroli E, et al. Treatment of erectile dysfunction due to C677T mutation of the MTHFR gene with vitamin B6 and folic acid in patients non responders to PDE5i. J Sex Med. 2010;7(1 Pt 1):216-223.

Ma H, He X, Yang Y, Li M, Hao D, Jia Z. The genus Epimedium: an ethnopharmacological and phytochemical review. J Ethnopharmacol. 2011;134(3):519-541.

MacKay D. Nutrients and botanicals for erectile dysfunction: examining the evidence. Altern Med Rev. 2004;9(1):4-16.

Maggi M, Buvat J, Corona G, Guay A, Torres LO.Hormonal Causes of Male Sexual Dysfunctions and Their Management (Hyperprolactinemia, Thyroid Disorders, GH Disorders, and DHEA). J Sex Med. 2012;23(10):1743-6109.

Malaguarnera M. Carnitine derivatives: clinical usefulness. CurrOpinGastroenterol. 2012;28(2):166-176.

Martin S, Atlantis E, Wilson D, et al. Clinical and Biopsychosocial Determinants of Sexual Dysfunction in Middle-Aged and Older Australian Men. J Sex Med. 2012;3(10):1743-6109.

Masuda H. Significance of nitric oxide and its modulation mechanisms by endogenous nitric oxide synthase inhibitors and arginase in the micturition disorders and erectile dysfunction.Int J Urol. 2008;15(2):128-134.

Mathers MJ, Brandt AS, Rundstedt F, Roth S, Sommer F, Klotz T. [Metabolism of nitric oxide (NO) and arginine: significance for male health]. Aktuelle Urol. 2009;40(4):235-241.

McVary KT. Clinical practice.Erectile dysfunction.The New England journal of medicine. Dec 13 2007;357(24):2472-2481.

MD Consult. Alprostadil. Available at: http://www.mdconsult.com/das/pharm/body/371041791-4/0/full/1184?infotype=4 Revised 8/27/2010. Accessed 10/8/2012.

MD Consult. Erectile Dysfunction. Available at: http://www.mdconsult.com/das/pdxmd/body/370348123-3/0?type=med&eid=9-u1.0-_1_mt_1014835 Updated: 2/10/2012a. Accessed 10/5/2012.

MD Consult. Ferri: Ferri's Clinical Advisor 2013, 1st ed. Peyronie’s Disease. 2012b. Accessed 10/8/12. Available at: http://www.mdconsult.com/books/page.do?sid=1364882619&eid=4-u1.0-B978-0-323-08373-7..00025-X--sc0135&isbn=978-0-323-08373-7&uniqId=371041791-6

MD Consult. Papaverine. Available at: http://www.mdconsult.com/das/pharm/body/371041773-2/0/full/1495. 12/2/2009b. Accessed 10/8/2012.

MD Consult. Phentolamine. Available at: http://www.mdconsult.com/das/pharm/body/371040816-2/0/full/481. Last updated 10/3/2009a. Accessed 10/8/2012.

Meldrum DR, Gambone JC, Morris MA, Esposito K, Giugliano D, Ignarro LJ. Lifestyle and metabolic approaches to maximizing erectile and vascular health.Int J Impot Res. 2012;24(2):61-68.

Meldrum DR, Gambone JC, Morris MA, Meldrum DA, Esposito K, Ignarro LJ. The link between erectile and cardiovascular health: the canary in the coal mine. Am J Cardiol. 2011;108(4):599-606.

Melnik T, Soares BG, Nasello AG. The effectiveness of psychological interventions for the treatment of erectile dysfunction: systematic review and meta-analysis, including comparisons to sildenafil treatment, intracavernosal injection, and vacuum devices. The journal of sexual medicine. Nov 2008;5(11):2562-2574.

Metz D, Weston P, Barker D. Case report of vasculitic rash induced by Ginkgo biloba and/or Horny Goat Weed. BMJ Case Rep. 2009;17:17.

Mingorance C, Rodriguez-Rodriguez R, Justo ML, Herrera MD, de Sotomayor MA. Pharmacological effects and clinical applications of propionyl-L-carnitine.Nutr Rev. 2011;69(5):279-290.

Morales A. Androgens are fundamental in the maintenance of male sexual health. CurrUrol Rep. 2011;12(6):453-460.

Morales A., Condra M, Owen JA, Surridge DH, Fenemore J, Harris C. Is yohimbine effective in the treatment of organic impotence? Results of a controlled trial. J Urol. 1987;137(6):1168-1172.

Moyad MA. Dietary supplements and other alternative medicines for erectile dysfunction. What do I tell my patients? UrolClin North Am. 2002;29(1):11-22.

Nair R, Sellaturay S, Sriprasad S. The history of ginseng in the management of erectile dysfunction in ancient China (3500-2600 BCE). Indian J Urol. 2012;28(1):15-20.

Nehra A, Jackson G, Miner M, et al. The Princeton III Consensus Recommendations for the Management of Erectile Dysfunction and Cardiovascular Disease. Mayo Clin Proc. 2012;87(8):766-778.

Ng CF, Lee CP, Ho AL, Lee VW.Effect of niacin on erectile function in men suffering erectile dysfunction and dyslipidemia. J Sex Med. 2011;8(10):2883-2893.

NIH (National Institutes of Health) Impotence.NIH Consens Statement. 1992;10(4):1-33.

NIH (National institutes of Health) MESH Terms: Arginine. Accessed 8/6/12. Available at: http://www.ncbi.nlm.nih.gov/mesh/68001120

Nikolova V, Stanislavov R, Vatev I, Nalbanski B, Punevska M. [Sperm parameters in male idiopathic infertility after treatment with prelox]. AkushGinekol. 2007;46(5):7-12.

Nunes KP, Labazi H, Webb RC. New insights into hypertension-associated erectile dysfunction.CurrOpinNephrolHypertens. 2012;21(2):163-170.

Nunes KP, Toque HA, Caldwell RB, Caldwell RW, Webb RC. Extracellular signal-regulated kinase (ERK) inhibition decreases arginase activity and improves corpora cavernosal relaxation in streptozotocin (STZ)-induced diabetic mice. J Sex Med. 2011;8(12):3335-44.

Oloyo AK, Sofola OA, Nair RR, Harikrishnan VS, Fernandez AC. Testosterone relaxes abdominal aorta in male Sprague-Dawley rats by opening potassium (K(+)) channel and blockade of calcium (Ca(2+)) channel. Pathophysiology. 2011;18(3):247-253.

Palmieri A, Imbimbo C, Creta M, Verze P, Fusco F, Mirone V. Tadalafil once daily and extracorporeal shock wave therapy in the management of patients with Peyronie's disease and erectile dysfunction: results from a prospective randomized trial. International journal of andrology. Apr 2012;35(2):190-195.

Paroni R, Barassi A, Ciociola F, et al. Asymmetric dimethylarginine (ADMA), symmetric dimethylarginine (SDMA) and L-arginine in patients with arteriogenic and non-arteriogenic erectile dysfunction. Int J Androl. 2012;20(10):1365-2605.

Petroczi A, Taylor G, Naughton DP. Mission impossible?Regulatory and enforcement issues to ensure safety of dietary supplements.Food ChemToxicol. 2011;49(2):393-402.

Pinsky MR, Chawla A, Hellstrom WJ.Intracavernosal therapy and vacuum devices to treat erectile dysfunction.Archivosespanoles de urologia. Oct 2010;63(8):717-725.

Porst H. The future of erectile dysfunction (ED). Arch Esp Urol. 2010;63(8):740-747.

Pushkar D, Segal AS, Bagaev AG, Nosovitskii PB.[Yohimbine in the treatment of erectile dysfunction].Urologiia. 2002;6:34-7.

Rashid A. The efficacy and safety of PDE5 inhibitors.Clinical Cornerstone. 2005;7(1):47-55.

Reiter WJ, Pycha A, Schatzl G, et al. Dehydroepiandrosterone in the treatment of erectile dysfunction: a prospective, double-blind, randomized, placebo-controlled study. Urology. 1999;53(3):590-594.

Reiter WJ, Schatzl G, Mark I, ZeinerA, Pycha A, Marberger M. Dehydroepiandrosterone in the treatment of erectile dysfunction in patients with different organic etiologies. Urol Res. 2001;29(4):278-281.

Ritchie R, Sullivan M. Endothelins& erectile dysfunction. Pharmacol Res. 2011;63(6):496-501.

Rooney M, Pfister W, Mahoney M, Nelson M, Yeager J, Steidle C. Long-term, multicenter study of the safety and efficacy of topical alprostadil cream in male patients with erectile dysfunction. The journal of sexual medicine. Feb 2009;6(2):520-534.

Rowland DL, Tai W. A review of plant-derived and herbal approaches to the treatment of sexual dysfunctions. J Sex Marital Ther. 2003;29(3):185-205.

Sadeghi-Nejad H, Brison D, Dogra V. Male Erectile Dysfunction. Ultrasound Clinics. 2007;2(1):57-71.

Saokaew S, Wilairat P, Raktanyakan P, Dilokthornsakul P, Dhippayom T, Kongkaew C, . . . Chaiyakunapruk N. Clinical Effects of Krachaidum (Kaempferia parviflora): A Systematic Review. Journal of evidence-based complementary & alternative medicine. Sep 30 2016.

Segal R, Burnett AL. Avanafil for the treatment of erectile dysfunction.Drugs Today. 2012;48(1):7-15.

Shamloul R. Natural aphrodisiacs. J Sex Med. 2010;7(1 Pt 1):39-49.

Shin BC, Lee MS, Yang EJ, Lim HS, Ernst E. Maca (L. meyenii) for improving sexual function: a systematic review. BMC Complement Altern Med. 2010;10:44.

Shindel AW, Xin ZC, Lin G, et al. Erectogenic and neurotrophic effects of icariin, a purified extract of horny goat weed (Epimedium spp.) in vitro and in vivo. J Sex Med. 2010;7(4 Pt 1):1518-1528.

Sorenson M, Grant WB. Does vitamin D deficiency contribute to erectile dysfunction? Dermatoendocrinol. 2012;4(2):128-136.

Srinivasan K. Black pepper and its pungent principle-piperine: a review of diverse physiological effects. Crit Rev Food SciNutr. 2007;47(8):735-48.

Stanislavov R, Nikolova V, Rohdewald P. Improvement of erectile function with Prelox: a randomized, double-blind, placebo-controlled, crossover trial. Int J Impot Res. 2008;20(2):173-180.

Stanislavov R, Nikolova V, Rohdewald P. Improvement of seminal parameters with Prelox: a randomized, double-blind, placebo-controlled, cross-over trial. Phytother Res. 2009;23(3):297-302.

Stanislavov R, Nikolova V. Treatment of erectile dysfunction with pycnogenol and L-arginine. J Sex Marital Ther. 2003;29(3):207-213.

Stein RI. Clinical Trial of Kaempferia parviflora extract for mild erectile dysfunction. Manuscript Under Review. 2018.

Stroberg P, Hedelin H, Bergstrom A. [Sex--only for the rich and healthy?PDE5 inhibitors too expensive for low income men].Lakartidningen. 2006;103(39):2865-2867.

Tamler R, Mechanick JI. Dietary supplements and nutraceuticals in the management of andrologic disorders.EndocrinolMetabClin North Am. 2007;36(2):533-552.

Tanweer MS, Fatima A, Rahimnajjad MK. Yohimbine can be the new promising therapy for erectile dysfunction in type 2 diabetics: J Pak Med Assoc. 2010 Nov;60(11):980.

Temkitthawon P, Hinds TR, Beavo JA, Viyoch J, Suwanborirux K, Pongamornkul W, . . . Ingkaninan K. Kaempferia parviflora, a plant used in traditional medicine to enhance sexual performance contains large amounts of low affinity PDE5 inhibitors. Journal of ethnopharmacology. Oct 11 2011;137(3):1437-1441.

Tep-Areenan P, Sawasdee P, Randall M. Possible mechanisms of vasorelaxation for 5,7-dimethoxyflavone from Kaempferia parviflora in the rat aorta. Phytotherapy research: PTR. Oct 2010;24(10):1520-1525.

Tharyan P, Gopalakrishanan G. Erectile dysfunction. ClinEvid. 2006;15(51):1227-1251.

Traish A, Kim NN, Moreland RB, Goldstein I. Role of alpha adrenergic receptors in erectile function. Int J Impot Res. 2000;12(1):S48-63.

Traish AM, Goldstein I, Kim NN. Testosterone and erectile function: from basic research to a new clinical paradigm for managing men with androgen insufficiency and erectile dysfunction. Eur Urol. 2007;52(1):54-70.

Ushiyama M, Kuramochi T, Yagi S, Katayama S. Antioxidant treatment with alpha-tocopherol improves erectile function in hypertensive rats. Hypertens Res. 2008;31(5):1007-1013.

Vardi Y, Appel B, Kilchevsky A, Gruenwald I. Does low intensity extracorporeal shock wave therapy have a physiological effect on erectile function? Short-term results of a randomized, double-blind, sham controlled study. The Journal of urology. May 2012;187(5):1769-1775.

Walle T, Otake Y, Brubaker JA, Walle UK, Halushka PV. Disposition and metabolism of the flavonoid chrysin in normal volunteers.Br J ClinPharmacol. 2001 Feb;51(2):143-6.

Wang CH, Huang YF. [Hyperhomocysteinemia and erectile dysfunction: an update]. Zhonghua Nan KeXue. 2011;17(11):1019-1022.

Wang X, Chu S, Qian T, Chen J, Zhang J. Ginsenoside Rg1 improves male copulatory behavior via nitric oxide/cyclic guanosine monophosphate pathway. J Sex Med. 2010;7(2 Pt 1):743-750.

Wannanon P, Wattanathorn J, Tong-Un T, Pangphukiew P, Muchimapura S, Sripanidkulchai B, Phachonpai W. EFFICACY ASSESSMENT OF KAEMPFERIA PARVIFLORA FOR THE MANAGEMENT OF ERECTILE DYSFUNCTION. OnLine J. of Biological Sciences: OnLine Journal of Biological Sciences. 2012;12(4):149-155.

Wattanathorn J, Pangphukiew P, Muchimapura S, Sripanidkulchai K, Sripanidkulchai B. Aphrodisiac Activity of Kaempferia parviflora. American Journal of Agricultural and Biological Sciences. 2012;7(2):114-120.

Wolfe SM. There have been inadequate warnings that erectile dysfunction drugs can cause blindness: MedGenMed. 2005 Dec 5;7(4):61.

Xin ZC, Kim EK, Lin CS, et al. Effects of icariin on cGMP-specific PDE5 and cAMP-specific PDE4 activities.Asian J Androl. 2003;5(1):15-18.

Yeh KY, Pu HF, Kaphle K, et al. Ginkgo biloba extract enhances male copulatory behavior and reduces serum prolactin levels in rats. HormBehav. 2008;53(1):225-231.

Zenico T, Cicero AFG, Valmorri L, Mercuriali M, Bercovich E. Subjective effects of Lepidiummeyenii (Maca) extract on well-being and sexual performances in patients with mild erectile dysfunction: a randomised, double-blind clinical trial. Andrologia. 2009;41(2):95-99.

Zhang J, Wang YB, Ma CG, et al. Icarisid II, a PDE5 inhibitor from Epimediumwanshanense, increases cellular cGMP by enhancing NOS in diabetic ED rats corpus cavernosum tissue. Andrologia. 2012;1:87-93.

Zhang Q, Radisavljevic ZM, Siroky MB, Azadzoi KM. Dietary antioxidants improve arteriogenic erectile dysfunction. Int J Androl. 2011;34(3):225-235.

Zheng BL, He K, Kim CH, et al. Effect of a lipidic extract from lepidiummeyenii on sexual behavior in mice and rats.Urology. 2000;55(4):598-602.