Around 30% of people with schizophrenia have a treatment-resistant form of the condition which does not respond well to antipsychotic drugs. Clozapine is the standard treatment for such patients although it can have serious side effects such as agranulocytosis (a low white blood cell count) and weight gain. However, a study of 40 schizophrenia patients in the U.S. has found that it may be the higher doses at which clozapine is prescribed rather than the drug itself which makes it effective in treating non-responsive schizophrenia. The study found that another drug, olanzapine, when used at a higher dose than usual was just as effective as clozapine. The treatment-resistant schizophrenia responded more slowly to higher doses of olanzapine and clozapine than other forms of the condition taking six months for an improvement to be felt rather than six weeks which was the case for the more treatment-responsive form of the condition.
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