Drug Interaction Report

MONITOR: Phenytoin may significantly decrease the effects of diazoxide and that diazoxide may significantly decrease the effects of phenytoin. The proposed mechanism is induction of phenytoin metabolism and clearance by diazoxide. Phenytoin reduces the half-life of diazoxide. Loss of seizure control has occurred.

MANAGEMENT: Caution and close observation are recommended if these drugs must be used together. Patients should be monitored for seizure activity and altered diazoxide effects (e.g., hypoglycemia).

MONITOR: Many psychotherapeutic and CNS-active agents (e.g., anxiolytics, sedatives, hypnotics, antidepressants, antipsychotics, opioids, alcohol, muscle relaxants) exhibit hypotensive effects, especially during initiation of therapy and dose escalation. Coadministration with antihypertensives and other hypotensive agents, in particular vasodilators and alpha-blockers, may result in additive effects on blood pressure and orthostasis.

MANAGEMENT: Caution and close monitoring for development of hypotension is advised during coadministration of these agents. Some authorities recommend avoiding alcohol in patients receiving vasodilating antihypertensive drugs. Patients should be advised to avoid rising abruptly from a sitting or recumbent position and to notify their physician if they experience dizziness, lightheadedness, syncope, orthostasis, or tachycardia. Patients should also avoid driving or operating hazardous machinery until they know how the medications affect them.