The pharmacokinetic and pharmacodynamic consequences of the co‐administration of lamotrigine and a combined oral contraceptive in healthy female subjects

A clinically relevant pharmacokinetic interaction was observed during co-administration of a combined oral contraceptive and lamotrigine. A dosage adjustment for lamotrigine may need to be considered when these agents are co-administered. A modest decrease in the plasma concentration of levonorgestrel was also observed but there was no corresponding hormonal evidence of ovulation.