Drug Interaction Report

Lamotrigine is a weak inhibitor of dihydrofolate reductase. Theoretically, coadministration with other dihydrofolate reductase inhibitors may have additive effects on rapidly proliferating tissues such as bone marrow, possibly increasing the risk of megaloblastic anemia and other hematologic adverse effects. However, a clinically significant interaction has not been reported. During prolonged human dosing, lamotrigine did not induce significant changes in the hemoglobin concentration, mean corpuscular volume, or serum or red blood cell folate concentrations for up to one year. No significant effects on red blood cell folate concentration have been observed for up to five years.

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.