A life-threatening idiosyncratic reaction characterised by muscle rigidity and hyperthermia, related to acute dopamine depletion, either from the use of neuroleptic drugs or of dopamine antagonists, or the withdrawal of dopamine agonists. Reported risk factors include dehydration and the concurrent use of lithium and tricyclic antidepressants. Acute myoglobinuric renal failure may occur. Intravenous fluids should be given to rapidly expand intravascular volume which is depleted due to dehydration, fever, shivering, tremors and vasodilation.
Crystalloid solutions are preferred.
Cooling measures should be instituted immediately to control hyperthermia. Muscle relaxants should be administered when hypertonia is present. Calcium channel blockers, such as nifedipine have been reported to reverse many NMS signs, such as hypertension, fever, tachycardia, urinary incontinence, rigidity and stupor. The mechanism is not yet clear. Dr Anthony Wong, Director, Jabaquara Poisons Center, Sao Paulo, Brazil.