Naltrexone blocks opioid receptors that are involved in the rewarding effects of drinking and the craving for alcohol. It reduces relapse to heavy drinking, defined as four or more drinks per day for women and five or more for men. Naltrexone cuts relapse risk during the first 3 months by about 36 percent but is less effective in helping patients maintain abstinence. It now comes in a once a month injection called Vivitrol.
Acamprosate (Campral) acts on the gamma-aminobutyric acid (GABA) and glutamate neurotransmitter systems and is thought to reduce symptoms of protracted withdrawal, such as insomnia, anxiety, restlessness, and dysphoria.
Disulfiram (Antabuse) interferes with degradation of alcohol, resulting in the accumulation of acetaldehyde, which, in turn, produces a very unpleasant reaction that includes flushing, nausea, and palpitations if the patient drinks alcohol. The utility and effectiveness of disulfiram are considered limited because compliance is generally poor. However, among patients who are highly motivated, disulfiram can be effective, and some patients use it episodically for high-risk situations, such as social occasions where alcohol is present. It can also be administered in a monitored fashion, such as in a clinic or by a spouse, improving its efficacy.
Topiramate is thought to work by increasing inhibitory (GABA) neurotransmission and reducing stimulatory (glutamate) neurotransmission. Its precise mechanism of action in treating alcohol addiction is not known, and it has not yet received FDA approval. Topiramate has been shown in two randomized, controlled trials to significantly improve multiple drinking outcomes, compared with a placebo. Over the course of a 14-week trial, topiramate significantly increased the proportion of patients with 28 consecutive days of abstinence or non-heavy drinking. In both studies, the differences between topiramate and placebo groups were still diverging at the end of the trial, suggesting that the maximum effect may not have yet been reached. Importantly, efficacy was established in volunteers who were drinking upon starting the medication.