Phenytoin and chlorpromazine in the treatment of spasticity.

The efficacy of phenytoin sodium and chlorpromazine hydrochloride in the reduction of spasticity was evaluated in both open and controlled studies. In each study, the majority of patients exhibited both objective and subjective signs of improvement. Reduction of motor tone in spastic muscles, as well as improvement in functiional status, was observed. Most patients experienced greater benefit from the combination of phenytoin and chlorpromazine than from either drug alone. The use of the drugs in combination permitted decreased chlorpromazine doses and reduced unwanted side effects such as lethargy and somnolence. These drugs may exert their action by suppressing fusimotor efferent as well as afferent discharged from muscle spindles. The results suggest that the fusimotor system is an important pharmacologic target in the treatment of spasticity.