Drug Interaction Report

MONITOR: A single case has been reported in which a patient developed seizures associated with elevated blood valproate levels after erythromycin was added to a stable valproate regimen. The seizures and elevated valproate levels resolved after both drugs were withheld. The patient subsequently tolerated her usual valproate dosage. The mechanism is suspected to be inhibition of the hepatic metabolism of valproate.

MANAGEMENT: While more data are needed, clinicians are encouraged to be aware that this interaction is possible when macrolide antimicrobial agents and valproate are coadministered. Patients should be advised to notify their physicians if they experience weakness, fatigue, confusion, ataxia, increased seizures, nausea, or vomiting.

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.