Paradoxical Autonomic Response to Procyclidine in the Neuroleptic Malignant Syndrome

     Martin V Balzan

Abstract:   Background: Neuroleptic Malignant Syndrome (NMS) is an adverse reaction to dopamine receptor antagonists, characterised by hyperpyrexia, extrapyramidal rigidity and impaired autonomic function. It might result from central dopamine receptor blockade that causes severe muscle contraction. Method: Case Study. Results: High dose intravenous therapy with the anticholinergic drug, procyclidine hydrochloride, temporarily diminished the muscle rigidity and reversed most of the autonomic features in a patient with NMS occurring after a single intramuscular dose of the dopamine antagonist metoclopramide. Paradoxically, however, the heart rate decreased and bowel movements increased with this atropine-like drug. Conclusion: Since the degree of tachypnoea, tachycardia, and bowel hypotonia closely paralleled the severity of the muscle rigidity, it is suggested that these autonomic features of NMS result from sustained muscle contraction rather than a direct effect of neuro-leptic drugs on the central nervous system.

Can. J. Neurol. Sci. 1995; 22: 244-246