Drug Interaction Report

ADJUST DOSE: Felbamate may decrease the hepatic metabolism of phenobarbital. Phenobarbital toxicity may result. In addition, phenobarbital may induce felbamate metabolism resulting in decreased felbamate concentrations. It may take up to 1 month to reach steady state phenobarbital concentrations.

MANAGEMENT: If this combination cannot be avoided, the phenobarbital dose may require a 25% reduction. Patients should be closely monitored for clinical response and phenobarbital toxicity (drowsiness, ataxia, lethargy) for at least one month after initiating concomitant therapy. Decreased phenobarbital doses may be required if felbamate is discontinued.

GENERALLY AVOID: Concurrent acute use of barbiturates and ethanol may result in additive CNS effects, including impaired coordination, sedation, and death. Tolerance of these agents may occur with chronic use. The mechanism is related to inhibition of microsomal enzymes acutely and induction of hepatic microsomal enzymes chronically.

MANAGEMENT: The combination of ethanol and barbiturates should be avoided.

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.