Correlation between plasma levels of prolactin and chlorpromazine in psychiatric patients.

Plasma levels of chlorpromazine (CPZ) and prolactin were measured repeatedly in 14 psychiatric patients throughout CPZ treatment. Mean prolactin level was elevated in 11 subjects (all six women and five of eight men). Mean plasma prolactin correlated significantly with mean plasma CPZ but not with the dose of the drug. Only patients with mean plasma prolactin above 35 ng/ml developed Parkinsonian side-effects.