Pharmacokinetics of a combined oral contraceptive in obese and normal-weight women

Westhoff, Carolyn L.; Torgal, Anupama H.; Mayeda, Elizabeth R.; Pike, Malcolm C.; Stanczyk, Frank Z.

doi:10.1016/j.contraception.2010.01.016

« Previous Next »Contraception
Volume 81, Issue 6 , Pages 474-480, June 2010

Pharmacokinetics of a combined oral contraceptive in obese and normal-weight women

Carolyn L. Westhoff
- Department of Obstetrics and Gynecology, Columbia University Medical Center, New York, NY 10032, USA
- Corresponding author. Tel.: +1 212 305 4805; fax: +1 212 305 6438.
Anupama H. Torgal
- Department of Obstetrics and Gynecology, Columbia University Medical Center, New York, NY 10032, USA
Elizabeth R. Mayeda
- Department of Obstetrics and Gynecology, Columbia University Medical Center, New York, NY 10032, USA
Malcolm C. Pike
- Department of Epidemiology and Biostatistics, Memorial Sloan-Kettering Cancer Center, New York, NY 10065, USA
- Department of Preventive Medicine, University of Southern California, Los Angeles, CA 90033, USA
Frank Z. Stanczyk
- Department of Obstetrics and Gynecology, Keck School of Medicine, University of Southern California, Los Angeles, CA 90033, USA

Received 7 December 2009; received in revised form 7 January 2010; accepted 14 January 2010. published online 22 February 2010.

Abstract

Background

This study was conducted to compare oral contraceptive (OC) pharmacokinetics (PK) in normal-weight [body mass index (BMI) 19.0–24.9] and obese (BMI 30.0–39.9) women.

Study Design

During the third week of the third cycle of OC use, we admitted 15 normal-weight and 15 obese women for collection of 12 venous specimens over 24 h. Using radioimmunoassay techniques, we measured levels of ethinyl estradiol (EE) and levonorgestrel (LNG). During the same cycle, women underwent twice-weekly sonography to assess ovarian follicular development and blood draws to measure endogenous estradiol (E2) and progesterone levels.

Results

Obese women had a lower area under the curve (AUC; 1077.2 vs. 1413.7 pg⁎h/mL) and lower maximum values (85.7 vs. 129.5 pg/mL) for EE than normal-weight women (p=.04 and <0.01, respectively); EE trough levels were similar between BMI groups. The similar, but smaller, differences in their LNG levels for AUC and maximum values (C_max) were not statistically significant. While peak values differed somewhat, the LNG trough levels were similar for obese and normal-weight women (2.6 and 2.5 ng/mL, respectively). Women with greater EE AUC had smaller follicular diameters (p=.05) and lower E2 levels (p=.04). While follicular diameters tended to be larger among obese women, these differences were not statistically significant.

Conclusion

OC hormone peak levels are lower among obese women compared to normal-weight women, but their trough levels are similar. In this small study, the observed PK differences did not translate into more ovarian follicular activity among obese OC users.

Keywords: Combined oral contraceptives, Pharmacokinetics, Obesity, BMI