Antipsychotic drug doses and adjunctive drugs in the outpatient treatment of schizophrenia

Abstract

This study investigated factors associated with the dose of antipsychotic medication prescribed at a schizophrenia unit outpatient clinic. The antipsychotic drug dose prescribed for 364 patients was converted to chlorpromazine equivalents (CPE) per day and concurrent prescriptions of lithium, carbamazepine, benzodiazepines, and antiparkinsonian drugs were recorded. We found that patients prescribed lithium, carbamazepine, and/or benzodiazepines as adjunctive drugs were receiving significantly higher doses of antipsychotic medication (p < 0.05). Patients prescribed both depot and oral neuroleptic drugs concurrently were receiving higher CPE-equivalent doses than those receiving either drug type alone (p < 0.05), and high-potency oral drugs were prescribed in higher CPE-equivalent doses than low-potency oral drugs (p < 0.05). Patients prescribed antiparkinsonian drugs were not receiving significantly higher CPE-equivalent doses of antipsychotic medication than patients not prescribed these drugs. There were no significant gender differences in the use of adjunctive drugs or in CPE-equivalent antipsychotic drug dose. Further research is needed to determine whether these findings are related to factors such as illness severity or to physician's prescribing practices.