Transient hypotensive effect of phenytoin in man

Phenytoin or an identically appearing placebo was administered in a double-blind fashion to 20 patients with mild essential hypertension. A significant fall in supine systolic blood pressure was noted 30 minutes to 1 hour after the oral administration of 100 mg phenytoin. No significant antihypertensive effect was observed after the patients had received 100 mg phenytoin every 8 hours for two weeks. Phenytoin had no effect on the diastolic blood pressure. It is concluded that the previously described hypotensive effect of phenytoin is a transient phenomenon which is of no therapeutic benefit in the long-term management of patients with essential hypertension.