Effectiveness of Hormonal Contraceptives in Patients with Higher Weights


Obesity is becoming more prevalent every year and as pharmacists, it is important to revisit current contraceptive options for these patients. Overweight patients are defined as having a BMI ranging from >25-29.9 kg/m2 and obese patients a BMI >30 kg/m2. Currently there are no safety contraindications in patients with a BMI > 25 kg/m2 alone when initiating oral contraceptives according to the current CDC guidelines; however, efficacy with these agents raises a valid question. We will address efficacy of both hormonal contraceptives as well as other modes of contraception.

Currently, there are several theories on how obesity can affect the efficacy of contraceptives. One theory is that the absorption of contraceptives may be increased due to the higher cardiac output that leads to increased blood flow, thus causing a faster gastric emptying of the drug meaning that the drug has less opportunity to be absorbed. Another thought is that higher levels of lipoprotein found in obese people may compete with drugs for binding sites on albumin, causing there to be more unbound drug. Furthermore, some studies revealed that there may be an association between obesity and a lower concentration of sex hormone-binding globulin. Hepatic metabolism and excretion of drugs may also be affected by obesity. While there isn’t one clear indication that may cause these discrepancies, there have been many studies conducted to test effectiveness in various types of contraceptives.

Importantly, there is a specific term used throughout research studies to determine efficacy of different contraceptive methods called Pearl Index (PI). PI is a numerical value used to indicate the number of pregnancies that occur for every 100 women per years of use. Additionally, some trials looked at the minimum serum concentrations of hormones that were necessary to suppress ovulation thus preventing pregnancy (levonorgestrel 0.3 ng/mL).

Combined Hormonal Contraceptives (CHCs)

One study compared a CHC that contained 30 mcg of ethinyl estradiol (EE) and 150 mcg of levonorgestrel (LNG) in normal-weight versus obese women. Obese women were found to have a lower AUC and Cmax of both EE and LNG, but clinically speaking, LNG levels were above 0.3 ng/mL in each population which is clinically significant enough to suppress ovulation and prevent pregnancy.

Another study evaluated the efficacy of an extended-cycle CHC that contained 20 mcg of EE and 100 mcg of LNG for 84 days, followed by 10 mcg EE for 7 days. The study concluded that pregnancy rates were similar across weight and BMI and did not report any significant discrepancies amongst weight classes.

Vaginal Rings

For the vaginal ring containing 11.7 mg of etonogestrel and 2.7 mg of ethinyl estradiol (NuvaRing®), there was a study that evaluated normal-weight versus obese women. Like the combined oral contraceptive pill, the ring did cause lower serum concentrations of hormones in obese women, but clinically there were no differences in ovarian follicle development. This suggests that efficacy is not compromised in obese women.

DMPA Injection

In a study that looked at the efficacy of the depot medroxyprogesterone acetate (DMPA) injection in women stratified by BMI, the serum concentrations were significantly lower in obese individuals compared to normal weight women. Surprisingly, these serum concentrations were sufficient to suppress ovulation and efficacy was not compromised.

Intrauterine Device (IUD)

In a large trial conducted on levonorgestrel-containing IUDs (two strengths, 8 mcg/24h or 13 mcg/24h), PIs revealed IUDs were effective at preventing pregnancy regardless of the patient BMI.

Exception: The Patch (Ortho Evra)

It is significant to note that obese women have lower efficacy with the hormonal contraceptive patch compared to other methods. Ortho Evra or Xulane (containing 6 mg norelgestromin, 0.75 mg ethinyl estradiol per patch) package insert states that from results of clinical trials, this patch may be less effective in women weighing greater than 90 kg. In trials conducted, it was reported that out of 15 pregnancies reported during the study, 5 of them were from a patient weighing more than 90 kg. The package insert also noted that women with a body weight >90 kg accounted for less than 3% of the study population, so it may be beneficial to conduct additional trials to determine efficacy of the patch for overweight patients.

In Conclusion

While elevated BMI alone is not a contraindication when initiating some contraceptives, it is important to recognize that overweight women are at a higher risk of comorbidities such as diabetes, hypertension, and thromboembolism which may be contraindications. If an individual only has an elevated BMI, CHCs, vaginal rings, or the DMPA injection may be appropriate to use given no clinically significant differences in their efficacy. It is important to advise overweight patients against using the hormonal patch due to the higher risk of unplanned pregnancies. Lastly, it is important to counsel patients that no contraceptive option is going to be 100% effective regardless of weight.


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About the Author

Samantha Kim, PharmD is a recent graduate of University of California San Diego Skaggs School of Pharmacy and Pharmaceutical Sciences.

Article reviewed by Breanna Failla, PharmD Candidate and Brooke Griffin PharmD, BCACP