- Aust Prescr 2002;25:120-3
- 1 October 2002
- DOI: 10.18773/austprescr.2002.117
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.
100 mg, 200 mg and 400 mg film-coated tablets
Approved indication: schizophrenia
Australian Medicines Handbook section 18.2
Amisulpride is a benzamide antipsychotic which antagonises dopamine receptors. It binds to the D2 and D3 dopamine receptors, but has little affinity for muscarinic or serotonin receptors. This pattern of activity differs from that seen with atypical antipsychotics.
The oral formulation has a bioavailability of 48%, but is not extensively metabolised. Most of the drug is excreted unchanged, with an elimination half-life of 12 hours. Clearance is reduced in patients with renal impairment.
A meta-analysis of trials which compared amisulpride with conventional antipsychotic drugs found that it had greater efficacy in patients with acute schizophrenia.1 Amisulpride has been compared with haloperidol in patients with chronic schizophrenia. After one year, a study of 60 in-patients found no significant difference in overall efficacy, but there was a trend suggesting amisulpride may be more beneficial for negative symptoms.2 Another larger study (488 patients) also found that amisulpride had a greater effect than haloperidol on negative symptoms.3
Like the atypical antipsychotics, amisulpride causes fewer extra pyramidal adverse effects than conventional drugs. Its extra pyramidal effects are dose related. Common adverse effects include insomnia, anxiety, agitation and weight gain. The release of prolactin may result in problems such as galactorrhoea and amenorrhoea. There is a potential for amisulpride to cause torsade de pointes as it prolongs the QT interval. Amisulpride is therefore contraindicated in combination with other drugs which cause QT prolongation. Caution is also advised if the patient is taking diuretics or other drugs which may cause hypokalaemia.
While amisulpride has effects which are similar to those of the atypical antipsychotics, there is little information about the relative benefits. One eight-week study found amisulpride and risperidone had similar efficacy in acute schizophrenia.4