The Effect of Oral Letermovir Administration on the Pharmacokinetics of a Single Oral Dose of P-Glycoprotein Substrate Digoxin in Healthy Volunteers.

Letermovir is a human cytomegalovirus (CMV) terminase inhibitor approved in the United States, Canada, Japan, and the European Union for prophylaxis of CMV infection and disease in CMV-seropositive, allogeneic, hematopoietic stem-cell transplant recipients. In vitro, letermovir is a substrate and potential modulator of P-glycoprotein. The potential of letermovir to alter the pharmacokinetics of digoxin (a P-glycoprotein substrate) upon coadministration in healthy subjects was therefore investigated in a phase 1 trial (EudraCT: 2011-004516-39). Oral letermovir 240 mg was administered twice daily for 12 days with a single oral digoxin 0.5-mg dose on day 7; after a washout period, oral digoxin 0.5 mg was administered on day 35 (sequence 1). The period order was reversed after a 28-day washout for sequence 2. Pharmacokinetics and safety were evaluated. The presence of steady-state letermovir reduced digoxin area under the plasma concentration-time curve from administration until last quantifiable measurement by 12% and maximum plasma concentration by 22% compared with digoxin alone; digoxin half-life and elimination rate remained similar in both conditions. The between-subject variability of digoxin maximum plasma concentration was higher with letermovir than without (42% vs 31%) and similar for digoxin area under the plasma concentration-time curve in both periods. No specific safety or tolerability concerns were identified. Overall, letermovir had no clinically relevant effect on concomitant administration with digoxin.

Pharmacokinetics and tolerability of lamotrigine and olanzapine coadministered to healthy subjects.

AIM: To assess the pharmacokinetic effect and tolerability of lamotrigine 200 mg day(-1) and olanzapine 15 mg day(-1) coadministration in healthy male volunteers. METHODS: Subjects were randomized to receive either lamotrigine titrated on days 1-42 with olanzapine added on days 43-56 (LTG + OLZ group; N = 16), lamotrigine titration with placebo added on days 43-56 (LTG group; N = 12), or placebo on days 1-42 with olanzapine added on days 43-56 (OLZ group; N = 16). Steady state (0-24 h) pharmacokinetic profiles were determined on day 56 in each group. RESULTS: The average (90% confidence interval) ratios of lamotrigine area under the concentration-time curve from 0 to 24 h and maximum observed concentration for the comparison of LTG + OLZ:LTG were 0.76 (0.65, 0.90) and 0.80 (0.71, 0.90), respectively. Olanzapine pharmacokinetics were essentially unaffected by lamotrigine. The most frequently reported adverse events (AEs) during combination therapy were fatigue, dizziness and mild transaminase elevations. These AEs occurred at similar frequencies in the LTG + OLZ and OLZ cohorts, while being less frequent or absent in the LTG group. CONCLUSIONS: Lamotrigine and olanzapine coadministration in patients who may benefit from the combination was supported by this study. Lamotrigine dosing schedules are recommended to remain unchanged when combined with olanzapine therapy. However, the possibility exists that the lamotrigine dose for some patients may need adjustment to optimize treatment when olanzapine is added to or withdrawn from a regimen including lamotrigine.

Lack of pharmacokinetic interaction between oxcarbazepine and lamotrigine.

Epilepsy and bipolar disorder are commonly treated by combination drug therapy, such as lamotrigine and oxcarbazepine. To ensure the safety of this combination, information on pharmacokinetics and tolerability must be available. The objective of study was to evaluate the pharmacokinetics and tolerability of coadministered lamotrigine and oxcarbazepine in healthy subjects. This randomized, single-blind, parallel-group study comprised three cohorts: lamotrigine (200 mg daily) plus oxcarbazepine (600 mg twice daily), lamotrigine (200 mg daily) plus placebo, and oxcarbazepine (600 mg twice daily) plus placebo. Serial blood samples were collected at steady state to determine serum concentrations of lamotrigine and plasma concentrations of oxcarbazepine and its active metabolite 10-monohydroxy metabolite (MHD). Pharmacokinetic parameters were determined by noncompartmental methods. Tolerability was monitored through adverse event reports, clinical laboratory results, vital signs, and electrocardiograms. A total of 47 male volunteers received study drugs. At steady state, lamotrigine AUC((0-24)) and C(max) were not significantly affected by oxcarbazepine co-therapy, nor were MHD AUC((0-12)) and C(max) significantly affected by lamotrigine co-therapy. The most common adverse events, headache, dizziness, nausea, and somnolence, occurred more frequently during lamotrigine and oxcarbazepine combination therapy than during the monotherapy. No significant changes in clinical laboratory parameters, vital signs, or electrocardiograms were reported. In conclusion, the combination of lamotrigine and oxcarbazepine does not require dose adjustments based on pharmacokinetic data. However, it is important to recognize that the combination therapy was associated with more frequent adverse events.