19.02.3 Antipsychotic Drug Indications and Drug Classes

Antipsychotics are indicated in the treatment of psychosis and symptoms of schizophrenia, and prevention of relapse.

Antipsychotic drugs are divided into two major classes. The first is the ‘typical’ or ‘first generation’ antipsychotics. Chlorpromazine was the prototype, a phenothiazine drug originally developed as an antihistamine agent. Subsequent to chlorpromazine, numerous typical antipsychotics were developed, forming the only types available until the late 1980’s. The second class is the ‘atypical’ or ‘second generation’ antipsychotics. The first of these developed was clozapine, found to be ‘atypical’ in that at therapeutic doses it was far less likely to cause adverse motor and hormone side effects seen with the ‘typical’ antipsychotics. Based on clozapine’s chemical structure and receptor binding properties, numerous atypical antipsychotics have been developed which now offer first line therapy in the treatment of schizophrenia.