Some of the views expressed in the following notes on newly approved products should be regarded as preliminary, as there may have been limited published data at the time of publication, and little experience in Australia of their safety or efficacy. However, the Editorial Executive Committee believes that comments made in good faith at an early stage may still be of value. Before new drugs are prescribed, the Committee believes it is important that more detailed information is obtained from the manufacturer's approved product information, a drug information centre or some other appropriate source.
333 mg enteric-coated tablets
Approved indication: alcohol dependence
Australian Medicines Handbook Section 18.6
Patients with alcohol dependence often relapse after treatment. Although psychological interventions are important, new drugs such as naltrexone (see `New drugs' Aust Prescr 1999;22:45-6) can help maintain abstinence. Acamprosate has also been approved for the prevention of relapse after detoxification.
Like naltrexone, the precise mechanism of action of acamprosate is uncertain. It has a chemical structure similar to gamma-aminobutyric acid (GABA), so acamprosate may stimulate inhibitory neurotransmission.
Patients begin treatment as soon as possible after the withdrawal period. The tablets are taken three times a day, with the dose being adjusted for bodyweight. Acamprosate is contraindicated if hepatic or renal function is significantly impaired. The tablets are slowly absorbed even if taken without food. It takes a week to reach a steady state. Most of the small proportion of the dose which is absorbed is excreted unchanged in the urine.
In a clinical trial, 224 patients were given acamprosate and compared with224 patients who took a placebo. The patients had not drunk alcohol for at least five days before starting treatment. Approximately 40% of the patients managed to continue treatment for a year. Of the 94 patients who had taken acamprosate for a year, 41 had been continuously abstinent. In the placebo group, only 16 of the 85 who completed treatment had been abstinent. In each group, 52 patients relapsed; most of the others were either lost to follow-up or stopped treatment.1
Not many patients withdrew from the studies of acamprosate because of adverse effects. More than 10% of patients will develop diarrhoea at the start of treatment. Less frequent adverse effects include rashes, abdominal pain and nausea and vomiting.
Although acamprosate can improve abstinence, its effects may decline with time. Of the 79 patients who completed 27 months of follow-up, only 27 remained abstinent.1 As the long-term benefits of acamprosate are unclear, it is important that it is only used as an adjunct to psychological and social treatments.
- Whitworth AB, Fischer F, Lesch OM, Nimmerrichter A, OberbauerH, Platz T, et al. Comparison of acamprosate and placebo in long-term treatment of alcohol dependence. Lancet 1996;347:1438-42.