A Cochrane review included 1 study comparing the efficacy and tolerability of olanzapine and haloperidol for the treatment of amphetamine-induced psychosis, with a total of 58 mainly male subjects. The average duration of amphetamine use prior to randomisation was 4.5 years. Dose range for both olanzapine and haloperidol was 5–20 mg/day for 4 weeks. 27/29 patients in the olanzapine group and 23/27 in the haloperidol group responded to treatment, defined as having 40% or greater Brief Psychiatric Rating Scale (BPRS) total improvement from baseline to endpoint. There was no difference in the number of adverse events experienced between these groups, except for extrapyramidal syndromes, which were reported only by haloperidol treated participants.
Comment: The quality of evidence is downgraded by imprecise results (few patients).