Purpose of review: Obesity continues to affect many women globally. In the USA, almost 40% of all women are obese and many of these women use hormonal contraception for pregnancy prevention. How well hormonal contraceptive works for these individuals has been an area of ongoing research. Pharmacokinetics (PK), the study of drug passage through the body, can shed light on how differences in physiology between obese and non-obese populations can impact drug disposition and subsequent efficacy. This review aims to reflect on these types of studies and empower clinicians with information to help tackle the challenges of the obesity epidemic and help them provide the best contraceptive options to their patients. Here, we present the basics of the mechanisms of action of hormonal contraception, fundamental pharmacokinetic principles, and the latest research into pharmacokinetics, obesity, and hormonal contraception.
Recent findings: New studies focused on the PK of hormonal contraception in women with obesity have shown that while there are distinct differences in how steroid hormones are processed in women with different body mass indices, contraceptive efficacy is likely the same. This is replicated in studies involving a variety of hormonal contraceptive methods.
Summary: PK studies allow for a detailed analysis of steroid hormone processing in individuals with obesity. Observing PK parameters at each stage of the passage of these hormones through the body, researchers have drilled down on physiologic differences that accompany obesity. In reviewing these PK parameter differences, however, it appears that while processes are different, the end result of pregnancy prevention is likely not compromised in the setting of obesity. Emergency contraception, which functions by a different mechanism from that of continuous hormonal contraception, is the one area in which obesity has been demonstrated to impact efficacy.
Keywords: Birth control; Effectiveness; Efficacy; Hormonal contraception; Obesity; Pharmacodynamics; Pharmacokinetics.