Schizophrenia is a serious mental illness which, for some people can become a long term problem. The usual first line treatment for schizophrenia is antipsychotic medication. However, because of the adverse effects these drugs can have, over time those taking them try to find a dose where they are gaining the most therapeutic benefit for the least amount of medication and doctors will often support them to do this. Conversely, for those whose illness does not respond well to medication, high doses are often used. This can cause severe adverse effects and can set up a cycle where individuals gain some benefit from the medication, develop side effects, then stop taking it and relapse. Therefore it would be helpful to find the optimum dose of each antipsychotic for different groups of people.
This review compares different doses of the antipsychotic risperidone, a drug introduced in the early 1990s and widely prescribed. Eleven trials were found comparing data for 2498 people. They were all under 12 weeks in length. Some looked at people in the first episode of schizophrenia or in an acute relapse, while others looked at those with a chronic long-term illness. For the purposes of this review doses of risperidone were divided into the following daily doses, ultra-low (less than 2mg), low (2mg - just less than 4mg), standard lower (4mg - just less than 6mg), standard higher (6mg - just less than 10mg) and high (10mg or more).
In the low and ultra low groups, there were a significant number of people leaving the study because of insufficient response, while those in the high dose group were more likely to leave the study for ‘any reason’ or ‘adverse event’. There were no significant differences between the standard lower and standard higher groups in improvement in general, or mental state, but both of these were better than an ultra low dose and gave less adverse effects than a high dose. There was some evidence to show that those in their first episode also respond well to a low dose. There were no good data on service use or quality of life. If further trials are conducted comparing different doses of risperidone, they should concentrate on specific groups of people, for example those in first episode or those with a chronic illness living in the community.
(Plain language summary prepared for this review by Janey Antoniou of RETHINK, UK www.rethink.org