Written by Marielle Jamgochian, MD

Combined oral contraceptives (COCs) are one of the most common birth control methods used today.¹ There are dozens of formulations of COCs, all of which contain an estrogen and a progestin. For pregnancy prevention, COC efficacy is similar across all formulations. Thus, choice of pill can be guided by the patient’s preferences, medical comorbidities, and cost. Those with anemia may benefit from a COC with added iron, but those with constipation may wish to avoid added iron. Those with heavy menstrual bleeding, who wish to time their bleeding, or who prefer no monthly bleeding may benefit from extended cycle formulations. There are also options for chewable or oral disintegrating tablets for patients who have trouble swallowing pills.

Hormone dosages vary in different pill formulations. Estrogen formulation is commonly ethinyl estradiol or estradiol valerate.² Dosage of ethinyl estradiol generally varies from 10 mcg (ultralow dosing) to 50 mcg (high dose). Generally, higher dose estrogens carry a higher risk of estrogen-related adverse effects, namely, risk of venous thromboembolism (VTE). However, there are no randomized controlled trials that demonstrate that there is a difference in rates of VTE between low doses (under 30 mcg), though risk of VTE in >50mcg doses is higher than doses <50mcg.³ In general, risk of VTE in any COC is lower than risk of VTE in pregnancy and postpartum.^4-6* Data supports use of 30 mcg dose or higher for adolescents as lower doses of ethinyl estradiol have been associated with impaired bone acquisition.⁷ Estradiol valerate may have lower risk of VTE though absolute risk of VTE in both groups is low.² Lower estrogen doses may confer increased risk of breakthrough bleeding, which may lead to discontinuation in some patients.⁸ 

Side effect profiles can differ by type of progestin. A newer progestin, drospirenone, is derived from spironolactone and structurally has anti-androgen and anti-mineralocorticoid effects.⁹ In a retrospective analysis of 2147 patients, patients reported greatest acne improvement on drospirenone-containing COC compared to other progestins.¹⁰ There is a potential increased risk of VTE with drospirenone.¹¹

Monophasic pills have one dose of hormone throughout. Biphasic, triphasic, and quadphasic formulations are also available with differing levels of hormone by week. Multiphasic formulations generally do not have any proven advantage over monophasic pills, however, they may make it more difficult to skip withdrawal bleeding. Other disadvantages include difficulty if a tablet is missed or if a pill pack is lost or damaged in the middle of a cycle.⁸ 

Traditional pills contain 21 days of active pills and 7 days of placebo, but other formulations are available, for example, shortened or no placebo pills, or placebo pills after extended cycle of active pill. Withdrawal bleeding was built into COCs to mimic a period when a patient takes placebo pills. There is no medical reason to have withdrawal bleeding while on COCs other than patient preference^8,12 Extended cyclic formulations have placebo pills every 3 months or every year for withdrawal bleeding. Monophasic pill packs can also be used for continuous dosing, though a patient will need extra pill packs to make up for skipped placebo pills. Continuous dosing may increase the chance of unexpected/unplanned breakthrough bleeding or spotting.¹² 

In summary, COCs offer reliable pregnancy prevention with flexibility to tailor formulations based on individual preferences, comorbidities, and side effect profiles. Understanding the differences in estrogen and progestin components allows clinicians to optimize tolerability for each patient. In general, most patients do not need a specially-chosen COC and can do well with any formulation.

*The studies cited in this Pearl use the term “women.” RHAP recognizes that this language is not inclusive of all people who seek care. A person’s biology does not determine their gender.

RHAP Resources:

Your Birth Control Choices Fact Sheet

Pill User Guide

Download and print our resources for free from our website or visit our store to buy physical copies!

Sources:

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