New data on lithium and haloperidol incompatibility.

The authors describe a case of combined lithium and haloperidol toxicity characterized by hyperpyrexia, severe rigidity, mutism, and development of irreversible tardive dyskinesia. This case is similar to four other cases described in the literature and to the neuroleptic malignant syndrome. The authors postulate that two types of combined lithium-neuroleptic toxicity occur: a neuroleptic malignant extrapyramidal syndrome and a lithium toxicity that occurs in combination with phenothiazines, primarily thioridazine. Possible mechanisms and preventive measures are discussed.