© 2005 American Thoracic Society
Melatonin for Patients with AsthmaSafety and Efficacy Are Still DubiousFrom the Authors:We thank Dr. Ng and colleagues for their interest in our paper, which shows improvement in subjective sleep quality in women with asthma after 4 weeks of melatonin treatment (1). Ng and coworkers express several concerns that we would like to address. We share the more general concern of Ng and colleagues with the fact that melatonin preparations are widely available to the public without regulatory approval and guarantee of purity. In our study, melatonin was verified by HPLC and FTIR. A certificate of analysis was provided by the manufacturer (Progressive laboratories, Irving, TX). As described by Ng and colleagues, Cavallo and Ritschel (2) did not find significant sex differences in melatonin pharmacokinetics. However, their study was designed to assess the effects of sexual maturation on melatonin pharmacokinetic properties, and groups studied were relatively small. Moreover, melatonin was not administered orally, but intravenously. In contrast, the more recent study by Fourtillan and coworkers (3) showed that bioavailability of oral melatonin is about threefold greater in females, with large interindividual variations. Therefore, recruiting only women into our study was justified, although we recognize that conclusions should not be automatically extended to males with asthma. Regarding the quality of the trial, we disagree with Ng and colleagues. All eligible patients were assigned to each group by simple randomization with rigorous allocation concealment. There were no withdrawals. One patient who completed the 4 weeks of treatment failed to attend the final evaluation. Available data from this patient, including adverse effects, asthma symptoms, and daily peak flow measurements were included in the analysis, as described in the article. It has not been stated in our paper that chronic use of melatonin is safe. In fact, although no significant side effects were reported during the treatment period, we have emphasized that additional work into long-term effects of melatonin should be performed before it can be recommended for patients with asthma. Reports of complications linked to melatonin treatment have been quoted in the paper and we are convinced that safety issues have been adequately addressed. Finally, contrary to the position of Ng and colleagues, we find it difficult to justify not investigating the effects of melatonin on sleep in asthma, considering there are already data showing it can improve sleep in other subject groups (4) and the magnitude of sleep problems in this patient population.
Universidade Federal do Ceará, Fortaleza, Brazil FOOTNOTES Conflict of Interest Statement: F.L.C. does not have a financial relationship with a commercial entity that has an interest in the subject of this manuscript; F.P.d.S.-J. does not have a financial relationship with a commercial entity that has an interest in the subject of this manuscript; V.M.S.d.B. does not have a financial relationship with a commercial entity that has an interest in the subject of this manuscript; P.F.C.d.B. does not have a financial relationship with a commercial entity that has an interest in the subject of this manuscript. REFERENCES
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