Large variations of plasma levels during maintenance treatment with depot neuroleptics.

Abstract

Stability of neuroleptic medication has been associated with optimal clinical effect and minimal side-effects. Depot administration is assumed to yield better stability. Thirty patients on depot neuroleptic treatment were followed during three years with repeated measurements of plasma level and concurrent ratings of clinical symptoms and side-effects. Of 120 blood samples 35 (29%) measurements were outside +/-2 s.d. measurement error (expected 5%). Perphenazine levels were more variable (46%) than haloperidol (25%) and flupenthixol (12.5%). No relationship was found between side-effect ratings and fluctuations of plasma levels. Depot neuroleptic medication does not eliminate a clinically unwanted and sometimes marked variation in plasma level.