Cerebrospinal fluid homovanillic acid patterns during neuroleptic treatment

Twenty-four psychotic patients were studied at two points during continuous neuroleptic treatment. Thirteen patients showed a tolerance pattern with respect to cerebrospinal fluid homovanillic acid following probenecid while 11 showed a nontolerance pattern. Patients who developed tolerance had significantly fewer symptoms and Parkinsonian side effects at approximately the fifth week of treatment.