OLANZAPINE - A SEROTONIN-DOPAMINE-RECEPTOR ANTAGONIST FOR ANTIPSYCHOTIC THERAPY

The pharmacology, pharmacokinetics, clinical efficacy, adverse effects , drug interactions, dosage and administration, and cost of olanzapine are reviewed. Olanzapine is a serotonin-dopamine-receptor antagonist indicated for use in the treatment of schizophrenia and other psychoti c disorders. The affinity of olanzapine for neuroreceptors is similar to that of clozapine. The drug is well absorbed from the GI tract; foo d has no effect. Olanzapine is more effective than placebo and equal t o haloperidol in reducing psychotic symptoms on two rating scales. How ever, unlike typical dopamine-receptor antagonists used for antipsycho tic therapy, olanzapine is more effective in reducing the negative sym ptoms of schizophrenia. The most frequent adverse drug reactions (ADRs ) associated with olanzapine are somnolence, agitation, insomnia, and headache. Constipation and dry mouth occur as dose-dependent ADRs. Unl ike clozapine, olanzapine does not cause agranulocytosis. No cases of tardive dyskinesia or neuroleptic malignant syndrome have been reporte d. Olanzapine has been associated with slight increases in hepatic tra nsaminases. More study is needed to determine whether olanzapine inter acts significantly with other drugs. The recommended starting dosage i s 5-10 mg orally once daily. Efficacy beyond six weeks has not been ev aluated; patients treated for longer than six weeks should be periodic ally reassessed. Olanzapine costs about 10 limes more than typical ant ipsychotics because a generic version is not available; however, olanz apine costs less than clozapine therapy and may cost less than haloper idol in terms of total health care costs. Olanzapine offers an effecti ve alternative for treating schizophrenia and has a favorable adverse- effect profile.