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Letters to the Editor

Dr Vieta Replies

See original letter by Evan Mayo-Wilson

Dr Vieta Replies

To the Editor: The letter by Dr Mayo-Wilson expresses concern about potential discrepancies between an internal company report1 and the article that we published on the effectiveness of adjunctive gabapentin in bipolar disorder.2 Discrepancies might result in publication bias, so I would like to provide further details on the study.

Ours was an investigator-initiated trial that was originally sponsored by Parke-Davis Spain (which had been bought by Pfizer at the time of publication). The study took a long time to complete and was published in 2006. By that time, gabapentin had become generic and had lost commercial interest. It was published, precisely, to avoid publication bias.3 Our study found that gabapentin was associated with modest improvements in a rough measure of clinical outcome but had no effects on preventing further episodes.2 The publication truly reflects the outcome of all the patients who fulfilled the prespecified inclusion criteria, and the interpretation of the results avoids, in my view, any uncritical support for the use of gabapentin as an adjunct to lithium in patients with bipolar disorder.

References

1. Vedula SS, Li T, Dickersin K. Differences in reporting of analyses in internal company documents versus published trial reports: comparisons in industry-sponsored trials in off-label uses of gabapentin. PLoS Med. 2013;10(1):e1001378. PubMed doi:10.1371/journal.pmed.1001378

2. Vieta E, Manuel Goikolea J, Martí­nez-Arán A, et al. A double-blind, randomized, placebo-controlled, prophylaxis study of adjunctive gabapentin for bipolar disorder. J Clin Psychiatry. 2006;67(3):473-477. PubMed doi:10.4088/JCP.v67n0320

3. Colom F, Vieta E. The need for publishing the silent evidence from negative trials. Acta Psychiatr Scand. 2011;123(2):91-94. PubMed doi:10.1111/j.1600-0447.2010.01650.x

Eduard Vieta, MD, PhD

evieta@clinic.ub.es

Author affiliation: Hospital Clinic, University of Barcelona, IDIBAPS, CIBERSAM, Barcelona, Catalonia, Spain.

Potential conflicts of interest: Dr Vieta has been a consultant to AstraZeneca, Bristol-Myers Squibb, Eli Lilly, Ferrer, Forest Research Institute, Gedeon Richter, GlaxoSmithKline, Janssen-Cilag, Jazz, Johnson & Johnson, Lundbeck, Merck, Novartis, Otsuka, Pfizer, Qualigen, Roche, Sanofi-Aventis, Servier, Schering-Plough, Shire, Solvay, Takeda, and Teva; has received grant/research support from AstraZeneca, Bristol-Myers Squibb, Eli Lilly, Forest Research Institute, Gedeon Richter, GlaxoSmithKline, Janssen-Cilag, Jazz, Johnson & Johnson, Lundbeck, Novartis, Otsuka, Pfizer, Sanofi-Aventis, Servier, and Teva; and has served on the speakers or advisory boards for AstraZeneca, Bristol-Myers Squibb, Eli Lilly, Forest Research Institute, Gedeon Richter, GlaxoSmithKline, Janssen-Cilag, Jazz, Johnson & Johnson, Lundbeck, Merck, Novartis, Otsuka, Pfizer, Qualigen, Roche, Sanofi-Aventis, Servier, Schering-Plough, Solvay, Takeda, and Teva.

Funding/support: The original article described in this letter was supported by Pfizer SA, Madrid, Spain.

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