Objective: To investigate the level of evidence supporting the use of common over-the-counter (OTC) agents (diphenhydramine, doxylamine, melatonin, and valerian) for occasional disturbed sleep or insomnia.
Data sources: A systematic review of the literature was conducted on July 31, 2014, using MEDLINE (PubMed) and the search terms (insomnia OR sleep) AND (over*the*counter OR OTC OR non*prescription OR antihistamine OR doxylamine OR diphenhydramine OR melatonin OR valerian) with the filters English, human, and clinical trials.
Study selection: Identified publications (from 2003 to July 31, 2014, following previous published literature reviews) that met the inclusion criteria were selected. The criteria included randomized placebo-controlled clinical studies that utilized overnight objective (polysomnography) or next-day participant-reported sleep-related endpoints and that were conducted in healthy participants with or without occasional disturbed sleep or diagnosed insomnia.
Results: Measures of efficacy and tolerability were summarized for each study individually and grouped according to OTC agent: H1 antagonists or antihistamines (3 studies, diphenhydramine), melatonin (8), and valerian or valerian/hops (7). Of the 3 sleep agents, studies conducted with melatonin, especially prolonged-release formulations in older individuals with diagnosed insomnia, demonstrated the most consistent beneficial effects (vs placebo) on sleep measures, specifically sleep onset and sleep quality, with favorable tolerability. In contrast, the clinical trial data for diphenhydramine, immediate-release melatonin, and valerian suggested limited beneficial effects.
Conclusions: A review of randomized controlled studies over the past 12 years suggests commonly used OTC sleep-aid agents, especially diphenhydamine and valerian, lack robust clinical evidence supporting efficacy and safety.