First-line treatment for uncomplicated primary constipation is to ensure adequate dietary fiber and fluid intake and physical activity level (Rao 2014; Basilisco 2013). These approaches are discussed in detail in the Diet and Lifestyle Considerations and Integrative Interventions sections.
If the diagnosis is secondary constipation, efforts should be made to treat the cause (eg, an underlying medical condition or medication side effect), but it may still be helpful for these patients to increase dietary fiber and fluids and to engage in regular physical activity (Rao 2014).
Methylcellulose and calcium polycarbophil. Methylcellulose and calcium polycarbophil are synthetic fibers commonly recommended to treat constipation, though there is little research into their effectiveness (Leung, Riutta 2011; Lembo 2003). Excessive gas and bloating are possible side effects of methylcellulose treatment (Rao 2014).
Laxatives are the first-line treatment for chronic constipation that persists despite dietary and lifestyle changes (Rao 2014). Fiber supplements are sometimes referred to as bulk laxatives. There are three other categories of laxatives: stool softeners or emollients, osmotic laxatives, and stimulants (Muller-Lissner 2013; Lembo 2003; Leung, Riutta 2011). Overall, studies show laxatives increase the number of bowel movements (Muller-Lissner 2013; Pare 2014), but 28‒75% of laxative users report not being satisfied with the results (Muller-Lissner 2013; Johanson 2007).
Laxatives, especially those of the stimulant variety, should not be used haphazardly or in excess, especially by those who take diuretics. Excessive laxative use in combination with diuretics can lead to potentially dangerous fluid and electrolyte imbalances (Sankar 1998). Even without diuretics, excessive laxative use—particularly stimulant laxatives—may cause electrolyte and fluid balance problems (Roerig 2010).
Stool softeners. Stool softeners, such as the commonly used docusate sodium, increase the water content of stool to facilitate elimination (Siegel 2005; Portalatin 2012). Mineral oil acts as a lubricant or emollient and is thought to facilitate easy passage of stool. Stool softeners are often the next choice of laxative when supplemental fiber is ineffective or not well tolerated (Leung, Riutta 2011), but there is little evidence demonstrating their effectiveness (Pare 2014).
Osmotic laxatives. Osmotic laxatives are unabsorbed compounds that attract water as they move through the colon (Basilisco 2013). Polyethylene glycol (PEG; Miralax), lactulose, sorbitol, glycerin, and magnesium hydroxide (Milk of Magnesia) are common osmotic laxatives, with PEG having the most evidence for increasing stool frequency and softness (Siegel 2005; Leung, Riutta 2011; Pare 2014). PEG has considerable side effects, however, including nausea, flatulence, and diarrhea, particularly in older individuals (Leung, Riutta 2011; Basilisco 2013).
Stimulant laxatives. Stimulant or irritant laxatives stimulate the enteric nerves that trigger peristalsis. They also inhibit water resorption and stimulate water secretion in the colon, keeping moisture in the stool. Bisacodyl (Dulcolax), sodium picosulfate, and senna are common stimulant laxatives. Senna is made from the pods of senna, or cassia, trees and is a source of plant chemicals called anthraquinones, which are the active component (Rama Reddy 2015; Franz 1993; Adamcewicz 2011). Both bisacodyl and senna have been shown to relieve constipation, but they frequently cause abdominal pain and diarrhea; therefore, they are best used short-term for acute constipation or long-term only in people who do not improve with other types of laxatives (Rao 2014; Roque 2015; Pashankar 2005; Connolly 1974; Basilisco 2013; Gartlehner 2007; Pare 2014; Leung, Riutta 2011). Overuse of stimulant laxatives may damage the neuromuscular system of the colon, aggravating constipation. Because many individuals attempt to remedy this problem with further use of stimulant laxatives, this condition has been referred to as “dependence” (Zhao 2012; Mayo Clinic 2014a; Mehler 2003).
Prosecretory agents. Much like stimulant laxatives, prosecretory agents cause the release of water into the intestines. Unlike osmotic laxatives, which attract and retain water molecules, prosecretory agents stimulate water flow into the intestine, reducing bowel transit time (Thomas 2015; Thayalasekeran 2013; Portalatin 2012).
There are two drugs in this category that have been approved the Food and Drug Administration (FDA): lubiprostone (Amitiza) and linaclotide (Linzess) (Thomas 2015). Clinical trials have shown that both of these medications can increase the frequency of bowel movements in individuals with chronic constipation and constipation-predominant irritable bowel syndrome (IBS-C) (Lee 2014; Liu 2011; Thayalasekeran 2013), and reduce the abdominal pain that characterizes IBS-C (Thayalasekeran 2013; Thomas 2015). However, only 20‒33% of patients in these trials had beneficial responses to the medications. Side effects may also limit the usefulness of these agents: nearly 20% of those with IBS-C and 16% of those with chronic constipation treated with linaclotide developed diarrhea, both significantly higher rates than in the placebo groups. The most common side effect associated with lubiprostone treatment was nausea. Temporary shortness of breath and chest pain were rarely observed; these adverse reactions may be attributable to intestinal distention. This class of medications has also been associated with urinary tract infections, sinusitis, abdominal pain or bloating, gas, and headache, although it is not clear whether the drugs caused all of these side effects (Thomas 2015).
Suppositories and Enemas
Rectal suppositories, made with laxatives like glycerine or bisacodyl, and enemas containing saline, tap water, and even soap suds can prompt immediate bowel emptying and are generally used on an as-needed basis to treat or prevent obstruction or impaction (Portalatin 2012; Roque 2015; Rao 2014).
Surgery is a last resort for people with severe intractable symptoms and diminished quality of life (Andromanakos 2015). Available data on the efficacy of surgical treatment is inconclusive (Lee 2014), but is unlikely to be beneficial in those with motility problems that extend to the small intestine and stomach (Rao 2014).