Clozapine rechallenge following neuroleptic malignant syndrome: A systematic review

Purpose/Background Neuroleptic malignant syndrome (NMS) has been described with most antipsychotics, most commonly first generation. Clozapine has also been associated with NMS. Methods/Procedures We conducted a systematic review to identify all studies investigating or describing (a) clozapine rechallenge following suspected NMS associated with clozapine, (b) clozapine use after suspected NMS associated with another antipsychotic, and (c) rechallenge with nonclozapine antipsychotics after suspected clozapine-associated NMS. Findings/Results We identified 51 reports detailing 67 cases. Thirty-eight described clozapine administration after NMS on a nonclozapine antipsychotic; 12 described a clozapine rechallenge after an NMS on clozapine monotherapy; and 17 described the use of nonclozapine antipsychotics after an NMS on clozapine. The outcome of clozapine rechallenge was favorable (no recurrence of NMS) in 92% (n = 11) of cases after an NMS on clozapine and in 79% (n = 30) of those prescribed clozapine following NMS on a nonclozapine antipsychotic. Most (82%; n = 14) cases after NMS on clozapine had no recurrence of NMS on receiving a nonclozapine antipsychotic. No mortality was reported with any of these interventions. Implications/Conclusions Our findings suggest that rechallenge following clozapine NMS is possible, and with careful risk-benefit analysis consideration, a clozapine rechallenge can be made. A publication bias in favor of cases in which rechallenge was successful is probable and is an important limitation.