to the editor: I would like to point out an easy, low-risk preventive therapy that the article on exercise-induced bronchoconstriction did not mention. Ascorbic acid (vitamin C) taken before exercise can be protective against exercise-induced asthma in some persons.1,2 The effective dose is 1,500 to 2,000 mg one hour before exercise. This therapy does not replace the need to have an albuterol inhaler available.
in reply: Thanks to Dr. Stevenson for mentioning the use of ascorbic acid as a protective agent in the management of exercise-induced asthma. Many different types of therapies have been used, from inhaled heparin to verapamil. I tried to limit this article to therapies with strong evidence-based support.
The studies Dr. Stevenson mentions are intriguing but have several deficiencies. The first deficiency is the number of participants in the study. The Cohen article1 had only 20 participants, and the Schachter study2 had only 12 participants. Another problem is that neither study uses exercise challenge testing protocols, which have been shown to be more sensitive and specific in detecting exercise-induced asthma. Lastly, the Cochrane Collaboration reviewed vitamin C supplementation for the treatment of asthma most recently in 2009.3 Both of these studies were found to have flaws in reporting quality, and the reviewers concluded that the evidence was insufficient to support the use of vitamin C in the management of asthma.
Although many possibly cheaper and simpler treatments may be useful in the management of exercise-induced asthma, physicians should favor evidence-based treatments until these other treatments have stronger evidence to support their use.