Drug Interaction Report

MONITOR: Coadministration with methsuximide may decrease the plasma concentrations of valproic acid. The exact mechanism of interaction is unknown. The interaction was reported in a study of pediatric patients ranging in age from 8 to 19 with epilepsy. In eight patients who had been receiving valproic acid with methsuximide, mean valproic acid serum level increased by 44% following the discontinuation of methsuximide. In 14 patients who had methsuximide added to stable valproic acid therapy, mean valproic acid serum level decreased by 32% following the addition of methsuximide.

MANAGEMENT: Caution is advised if methsuximide and valproic acid are used in combination. Pharmacologic response and serum valproic acid level should be monitored more closely whenever methsuximide is added to or withdrawn from stabilized therapy, and the dosage(s) of the drugs adjusted as necessary.

GENERALLY AVOID: Alcohol may potentiate some of the pharmacologic effects of CNS-active agents. Use in combination may result in additive central nervous system depression and/or impairment of judgment, thinking, and psychomotor skills.

MANAGEMENT: Patients receiving CNS-active agents should be warned of this interaction and advised to avoid or limit consumption of alcohol. Ambulatory patients should be counseled to avoid hazardous activities requiring complete mental alertness and motor coordination until they know how these agents affect them, and to notify their physician if they experience excessive or prolonged CNS effects that interfere with their normal activities.

GENERALLY AVOID: Alcohol may potentiate some of the pharmacologic effects of CNS-active agents. Use in combination may result in additive central nervous system depression and/or impairment of judgment, thinking, and psychomotor skills.

MANAGEMENT: Patients receiving CNS-active agents should be warned of this interaction and advised to avoid or limit consumption of alcohol. Ambulatory patients should be counseled to avoid hazardous activities requiring complete mental alertness and motor coordination until they know how these agents affect them, and to notify their physician if they experience excessive or prolonged CNS effects that interfere with their normal activities.