Unknown Health Risks of Inhaled InsulinSeptember 2007
By T.R. Shantha, MD, PhD, FACA
Potential Health Risks of Inhaled Insulin Therapy
Other questions still remain unresolved about the potential health risks of inhaled insulin. Among the documented and possible health risks of insulin inhalation therapy are:
1. Increased risk of respiratory tract irritation, causing cough, shortness of breath, sore throat, and dry mouth.12
2. Development of hypoglycemia, with adverse outcomes in those who exercise immediately after inhalation and those who smoke. These effects may occur due to the rapid absorption of inhaled insulin from the alveoli.13-15
3. Exacerbation of existing conditions in asthmatics who require more inhaled insulin to control their blood sugar.16 Furthermore, inhaled insulin could lead to airway smooth muscle contraction, which could precipitate or exacerbate chronic obstructive pulmonary disease or episodes of asthma.17
4. Alveolar thickening, poor gas exchange, pulmonary hypertension, or pulmonary fibrosis. Additionally, inhaled insulin could cause adverse effects in people with pre-existing respiratory diseases such as chronic bronchitis, tuberculosis, tumors, and other chronic lung afflictions.18
5. Increase in insulin anti-bodies. In one study, inhaled insulin increased the level of insulin anti-bodies in the body from baseline levels of 6% to 35%.19 This could have the adverse effect of retarding the action of soluble insulin in the blood, since the removal of an insulin immune complex could make less insulin available to lower blood sugar.
6. Unknown long-term effects of supraphysiologic doses of insulin in the human lung or on neoplastic lung tissue. It is possible that insulin could stimulate unwanted tissue growth in normal and precancerous cells, which could lead to genetic defects and ultimately to cancer.
7. Potentially increased tumor incidence in the tissues of the respiratory tract, although no evidence of this has been presented to date.
The true health risks could take a long time to come to light, as occurred with other drugs such as Vioxx® (an anti-inflammatory) and Avandia® (an oral anti-diabetic drug). In addition to the eye-opening health risks of inhaled insulin, it is more expensive than other insulin preparations.
Should You Use Inhaled Insulin?
I recommend that inhaled insulin should not be used in smokers or in patients with underlying lung diseases such as asthma or chronic obstructive pulmonary disease. Until the drug’s full health risks are known, I further discourage its use in those with precancerous lesions (such as polyps, dysplasia, or the leukoplakia that can accompany tobacco use). Inhaled insulin is not approved for use in pregnant women, children, or adolescents. I hope that the FDA and drug companies involved in licensing and developing an inhaled method of insulin delivery will fully investigate these health risks and concerns on a post-approval surveillance basis. The future of insulin delivery with the fewest side effects may come from development of slow-release injectable insulin lasting days to weeks with a single shot, or from implantation of insulin-producing stem cells.
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