Variability in repeat serum etonogestrel concentrations among contraceptive implant users during the steady-release pharmacokinetic period.

Aaron Lazorwitz, Jeanelle Sheeder, Stephanie Teal

Contraception 2022 Apr

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To assess the variability of repeated measurements of serum etonogestrel concentration among contraceptive implant users. We measured 3 consecutive serum etonogestrel concentrations, drawn weekly, in women using etonogestrel implants for 12 to 36 months. We used a repeated measures test to evaluate differences. Among 20 participants, repeat serum etonogestrel concentrations did not differ from initial measurements (Friedman's test, p = 0.95). Mean serum etonogestrel concentrations had similar 95% confidence intervals at each time point: (134.09, 201.46), (135.08, 237.46), and (132.66, 192.45). We confirm that single-time measurements of serum etonogestrel concentration are acceptable pharmacokinetic outcomes for etonogestrel implant studies. Pharmacokinetic studies of the etonogestrel contraceptive implant assume single-time measurements are stable steady-state estimates based on small studies using older analysis methods. Our repeated measures study using modern liquid-chromatography mass-spectrometry analysis methods provides updated support for single-time pharmacokinetic measurements among etonogestrel implant users. Copyright © 2021. Published by Elsevier Inc.

Citation

Aaron Lazorwitz, Jeanelle Sheeder, Stephanie Teal. Variability in repeat serum etonogestrel concentrations among contraceptive implant users during the steady-release pharmacokinetic period. Contraception. 2022 Apr;108:65-68