Acamprosate, a drug that has a similar structure to the neurotransmitter gamma-aminobutyric acid, appears useful in helping persons with alcohol dependence to maintain abstinence, according to a new review of studies on the topic. The researchers examined the evidence for this approved use of the drug, as well as what is known about its pharmacokinetics, interactions with other drugs, safety, and tolerability.
In three European studies, the drug was evaluated as an adjunct to psychotherapy in 998 patients who had undergone detoxification and were no longer using alcohol. The studies found that acamprosate was more effective than placebo in maintaining abstinence from alcohol. Studies in the United States, which involved patients who were not detoxified and abstinent before they were randomly assigned to receive the drug or a placebo, failed to show the same degree of efficacy for acamprosate, perhaps because the studies included patients who abused multiple substances. The shorter duration of abstinence required before treatment may also have selected patients who were less likely to maintain long-term abstinence.
Patients in one U.S. study who had a goal of total abstinence from alcohol and were highly motivated toward this goal had better outcomes with acamprosate than with placebo, despite an overall inability to demonstrate efficacy of acamprosate in this study. Studies involving comparison of acamprosate with naltrexone had widely mixed results, but acamprosate was never found to be superior to naltrexone in primary efficacy comparisons. Combination therapy using both drugs was more efficacious than acamprosate alone, but was not shown to be superior to naltrexone only.
Clinical trials and postmarketing surveillance showed that acamprosate is safe and well-tolerated. Combining data from 11 studies that used self-report of adverse events that occurred during treatment, similar rates occurred with acamprosate (61 percent) and placebo (56 percent). Most of the acamprosate adverse events, such as diarrhea, disappeared with time and were mild-to-moderate in severity. Withdrawal rates from short-term (<26 weeks) or longer-term (>48 weeks) studies were similar for patients receiving acamprosate or placebo, ranging from 6 to 8 percent.
The review was funded in part by the Agency for Healthcare Research and Quality through the Centers for Education and Research on Therapeutics (CERTs) program (HS16094). More information on the CERTs program can be found at http://www.certs.hhs.gov.
More details are in "Acamprosate," by William Klugh Kennedy, Pharm.D., Megan Leloux, Pharm.D., Eric C. Kutscher, Pharm.D., and others in Expert Opinion on Drug Metabolism and Toxicity 6(3), pp. 363-380, 2010.