Neuroleptic Malignant Syndrome and Dopaminergic Blockade

After receiving 90 mg of haloperidol and 100 mg of chlorpromazine hydrochloride within 25 hours, a 29-year-old man was found to have neuroleptic malignant syndrome (NMS), characterized by the acute onset of hyperpyrexia, extreme muscular rigidity, autonomic instability, and coma. Subsequently, rhabdomyolysis developed, with myoglobinuric renal failure and bilateral anterior tibial compartment syndromes. The patient's initial neuroleptic levels were in the therapeutic and nontoxic ranges. He was treated with supportive measures and his clinical improvement was paralleled by decreased neuroleptic levels, a return toward normal of an elevated prolactin level, and an increased responsiveness to a dopamine hydrochloride infusion. This supports an association between NMS and dopamine receptor blockade.