Clozapine is recommended for schizophrenic patients who have failed to respond to ≥2 separate courses of conventional antipsychotics from different drug classes. It is also appropriate for patients who experience severe extrapyramidal reactions with conventional antipsychotics, or who develop tardive dyskinesia on long term therapy.
Clozapine is more effective against the negative symptoms of schizophrenia than conventional antipsychotics and causes fewer extrapyramidal effects.
The main limitation with clozapine is the significant risk of agranulocytosis (1 to 2%). Regular monitoring of white blood cell counts (weekly during the first 18 weeks of treatment and every 2 weeks thereafter) reduces the incidence of this serious complication, but increases the cost of treatment.
Cost savings are possible with clozapine, relative to conventional antipsychotics. These usually result from reduced utilisation of hospital services, but are partially offset by increased use of community facilities. Up to 2 years of clozapine therapy may be required before economic benefits are apparent.