Validation of 24-hour trough concentration as a proxy for intensive pharmacokinetic measurements for a combined oral contraceptive pill containing desogestrel.

OBJECTIVES

To confirm that 24-hour steady-state trough measurements (C24) are high-quality proxies for gold standard pharmacokinetic measurements (area under the curve [AUC]) of a combined oral contraceptive pill (COCP).

STUDY

DESIGN

We conducted a 12-sample, 24-hour pharmacokinetic study in healthy reproductive-age females taking a COCP containing 0.15-mg desogestrel (DSG) and 30-μg ethinyl estradiol (EE). As DSG is a pro-drug for etonogestrel (ENG), we calculated correlations between steady-state C24 and 24-hour AUC values for both ENG and EE.

RESULTS

Among 19 participants at steady state, C24 measurements were highly correlated with AUC for both ENG (r = 0.93; 95% CI 0.83-0.98) and EE (r = 0.87; 95% CI 0.68-0.95).

CONCLUSIONS

Steady-state 24-hour trough concentrations are high-quality proxies for gold standard pharmacokinetics of a DSG-containing COCP.

IMPLICATIONS: Use of single-time trough concentration measurements at steady state provides excellent surrogate results for gold standard AUC values for both DSG and EE among COCP users. These findings support that large studies exploring interindividual variability in COCP pharmacokinetics can avoid the time- and resource-intensive costs associated with measuring AUC.

CLINICAL TRIAL REGISTRATION: Clinicaltrials.gov, NCT05002738.