Related Experiment Video
Updated: Oct 8, 2025

Validation of Therapeutic Agent Conjugation to Polyvinyl Alcohol-Coated Medical Devices
Published on: November 29, 2024
Variability in repeat serum etonogestrel concentrations among contraceptive implant users during the steady-release
Aaron Lazorwitz1, Jeanelle Sheeder1, Stephanie Teal2
1University of Colorado Anschutz Medical Campus, Department of Obstetrics and Gynecology, Division of Family Planning, Aurora, CO, United States.
Objective:
To assess the variability of repeated measurements of serum etonogestrel concentration among contraceptive implant users.
Study Design:
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.
Results:
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).
Conclusion:
We confirm that single-time measurements of serum etonogestrel concentration are acceptable pharmacokinetic outcomes for etonogestrel implant studies.
Implications:
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.
More Related Videos
Related Concept Videos
Dosage Regimen: Multiple Oral Dosage
Determination of Multiple Dosing Parameters: Steady-State, Minimum and Maximum Concentrations
Drug Accumulation During Multiple Dosing: Repetitive IV Injections
Drug Accumulation During Multiple Dosing: Intermittent IV Infusions
Pharmaceutical Alternatives: Stability-Related Therapeutic Nonequivalence
Steady State Concentration
Most drugs are administered in repeated doses at fixed intervals or through continuous...

