Written by Sairah Cherian, Pharm.D. and Regina Ginzburg, Pharm.D., CDCES, BC-ADM

Combined oral contraceptives (COC) consist of an estrogen and progestin and work synergistically to prevent pregnancy. Progestin is the main component of contraception and suppresses ovulation by decreasing luteinizing hormone. It also thickens the cervical mucus to inhibit sperm penetration, and thins the uterine lining to prevent egg implantation.^1,2 Estrogen stabilizes the endometrium and reduces irregular bleeding. Monophasic COCs contain the same amounts of estrogen and progestin throughout the active pills, whereas multiphasic COCs contain variable amounts of the hormones in an attempt to mimic the body’s hormone fluctuations. Although both are equally effective, monophasic tablets may be preferred because adverse effects are easier to identify and manage, and it’s easier to induce amenorrhea than with multiphasic formulations.² All COC types have a more lenient missed dosing regimen compared to traditional progestin-only pills (POPs), where the medication can be taken any time within 24 hours of the missed dose. 

POPs contain either norethindrone, norgestrel, or drospirenone. These are synthetic hormones derived from testosterone, progesterone, or spironolactone.^2,3 They remain a viable option for patients who cannot take estrogen due to its contraindications. Norethindrone POPs are commonly prescribed due to their long-standing safety and efficacy, as well as its low cost. More recently, the FDA approved norgestrel POP as an over-the-counter medication.⁴ Norethindrone and norgestrel POPs require a stricter dosing schedule and should be taken at the same time every day to maintain effectiveness. This is because the drug peaks at 2 hours but returns to near baseline at ~24 hours.⁵ If taken past 3 hours of its scheduled time, backup contraception is needed.^5,6 Drospirenone POPs are newer and have both antiandrogenic and antimineralocorticoid effects, which can help improve acne and bloating, but are more expensive. Drospirenone POPs also suppress ovulation, which provides a longer missed pill window of 24 hours, allowing greater flexibility compared with norethindrone. People may experience more unpredictable bleeding compared to COCs.  

Choosing the right oral contraceptive depends on specific patient factors. Understanding the differences among the estrogen and progestin components of oral contraceptives can guide providers and patients in selecting the most appropriate option. The table provides examples of various oral contraceptive types. 

RHAP Resources:

Your Birth Control Choices Fact Sheet

Pill User Guide

Progestin-Only Pill (POP) User Guide

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Sources:

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