Clozapine: plasma levels and prolactin response.

Serial plasma clozapine levels and serum prolactin levels were determined in two schizophrenic patients receiving clozapine, a novel antipsychotic drug. Despite marked therapeutic response and substantial clozapine blood levels, prolactin levels obtained 11--12 h after the last oral dose were unaffected or only minimally elevated. This confirms previous evidence of clozapine's unusual characteristics.