The effects of lamotrigine on the pharmacokinetics of lithium: Lithium pharmacokinetics with lamotrigine

Aims The treatment of bipolar disorder often includes use of multiple drug therapies. Lithium is one of the most commonly used treatments, but has a narrow therapeutic window. Lamotrigine, an established antiepileptic drug, is emerging as a potentially important new therapy in the treatment of bipolar disorder. The objective of this two-treatment crossover study was to determine whether lamotrigine affects lithium pharmacokinetics. Methods Twenty healthy adult men completed the study. Subjects took 2 g lithium gluconate anhydrous every 12 h in the morning and evening for 5 days and in the morning of day 6, with or without 100 mg lamotrigine once daily in the morning for 6 days. Blood and urine samples were collected on day 6 of both treatments to characterize the pharmacokinetics of lithium using noncompartmental methods. Results The geometric least-square mean ratio for renal clearance of lithium between the combination treatment and lithium alone treatment was 0.93 (95% confidence interval 0.85-1.02). Both treatments were well tolerated. Conclusions Lamotrigine does not cause significant change in the pharmacokinetics of lithium.