Comparative efficacy of phenytoin, steroid and carbamazepine in herpes zoster and post herpetic neuralgia

Three hundred patients of different ages were sequentially assigned three therapy groups (100 in each group) viz. phenytoin, steroid (prednisolone) and carbamazepine. Effect of these drugs on herpes zoster neuralgia and in prevention of post herpetic neuralgia was studied. Phenytoin was found to be superior to both steroid and carbamazepine in relieving the pain of herpes zoster and in reducing the incidence of post herpetic neuralgia. Only 16.1% of the patients in phenytoin treated group developed post herpetic neuralgia lasting for 2-4 weeks while 22.7% and 29.6% of the steroid and carbamazepine treated patients respectively developed post herpetic neuralgia and that too lasting for longer duration. No patient under 40 years developed post herpetic neuralgia.