• Beatrice A Golomb, Laura C Erickson, Sabrina Koperski, Deanna Sack, Murray Enkin, and Jeremy Howick.
• University of California, San Diego, School of Medicine, San Diego, California, USA. bgolomb@ucsd.edu
• Ann. Intern. Med. 2010 Oct 19; 153 (8): 532-5.

BackgroundNo regulations govern placebo composition. The composition of placebos can influence trial outcomes and merits reporting.PurposeTo assess how often investigators specify the composition of placebos in randomized, placebo-controlled trials.Data Sources4 English-language general and internal medicine journals with high impact factors.Study Selection3 reviewers screened titles and abstracts of the journals to identify randomized, placebo-controlled trials published from January 2008 to December 2009.Data ExtractionReviewers independently abstracted data from the introduction and methods sections of identified articles, recording treatment type (pill, injection, or other) and whether placebo composition was stated. Discrepancies were resolved by consensus.Data SynthesisMost studies did not disclose the composition of the study placebo. Disclosure was less common for pills than for injections and other treatments (8.2% vs. 26.7%; P = 0.002).LimitationJournals with high impact factors may not be representative.ConclusionPlacebos were seldom described in randomized, controlled trials of pills or capsules. Because the nature of the placebo can influence trial outcomes, placebo formulation should be disclosed in reports of placebo-controlled trials.

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