Treatment with liraglutide--a once-daily GLP-1 analog--does not reduce the bioavailability of ethinyl estradiol/levonorgestrel taken as an oral combination contraceptive drug.
Level 2 - randomized trial
Individual randomized controlled pharmacokinetic trial
PubMed 21228406 · doi:10.1177/0091270010389471
What was done
A randomized controlled trial assessed the pharmacokinetic impact of liraglutide on a single co-administered oral combination contraceptive containing ethinyl estradiol and levonorgestrel. The study included 21 healthy postmenopausal women. Serial blood samples were collected up to 74 hours post-dosing during liraglutide and placebo treatments to compare total exposure (AUC), maximum concentration (Cmax), and time to peak concentration.
What was found
Total exposure (AUC) for ethinyl estradiol was equivalent between liraglutide and placebo (AUC ratio 1.06; 90% CI, 0.99–1.13). Levonorgestrel total AUC was 18% higher with liraglutide (ratio 1.18; 90% CI, 1.04–1.34), while levonorgestrel AUC(0-t) met bioequivalence criteria (ratio 1.15; 90% CI, 1.06–1.24). Peak concentrations did not meet formal bioequivalence limits: ethinyl estradiol Cmax was 12% lower and levonorgestrel Cmax was 13% lower with liraglutide compared to placebo. Peak concentration occurred approximately 1.5 hours later for both components under liraglutide treatment.
Why it matters
Because GLP-1 receptor agonists delay gastric emptying, there is concern they might impair oral contraceptive efficacy. These findings indicate that liraglutide slows absorption rate but does not reduce overall bioavailability, suggesting contraceptive efficacy is unlikely to be compromised.
Limits
The study evaluated only 21 participants, all of whom were postmenopausal women rather than women of reproductive age. Only a single oral contraceptive dose was tested rather than steady-state chronic co-administration, and clinical contraceptive efficacy was not directly measured.
Cited by
- contradicts The delay in gastric emptying caused by GLP-1 receptor agonists can prevent oral medications, such as birth control pills, from being effectively absorbed.