Progestin-Only Pills: Available Formulations
Progestin-only pills (POPs) are available in the United States primarily as norethindrone formulations (first-generation progestin) and drospirenone formulations (fourth-generation progestin). 1, 2
Specific POP Formulations
First-Generation Progestin POPs
- Norethindrone is the most commonly available first-generation progestin-only pill in the United States 1, 2
- These traditional POPs contain lower doses of progestins and require strict adherence to timing—must be taken within 3 hours of the same time each day 3
- If a dose is missed by more than 3 hours, backup contraception should be used for 2 consecutive days of correct pill use 3
Fourth-Generation Progestin POPs
- Drospirenone represents a newer fourth-generation progestin-only pill option 1
- Fourth-generation progestins are chemically modified to provide anti-androgenic and/or anti-mineralocorticoid activity 1
Other Progestin Formulations (Less Common in US)
- Desogestrel POPs are available in some countries and have shown contraceptive effectiveness similar to combined oral contraceptives, though availability in the US is limited 4
Key Distinguishing Features of POPs
Mechanism of Action
- POPs work primarily by thickening cervical mucus rather than consistently inhibiting ovulation 3
- They do not consistently suppress ovulation, which contributes to their lower effectiveness compared to combined hormonal methods 3
Effectiveness Considerations
- With typical use, approximately 9 out of 100 women become pregnant in the first year of using POPs 3
- Efficacy ranges between 1.4 and 4.3 pregnancies per 100 woman-years of use, with lower pregnancy rates achieved in centers with good counseling 5
Appropriate Candidates for POPs
Ideal Users
- Breastfeeding women are particularly appropriate candidates, as POPs do not affect milk production 3
- Women with contraindications to estrogen, including those with history of venous thromboembolism, hypertension, or positive antiphospholipid antibodies 3
- POPs do not increase venous thromboembolism risk in healthy women (RR 0.90,95% CI 0.57-1.45) 3
Less Ideal Candidates
- POPs are generally not recommended as first-choice contraceptives for healthy adolescents due to strict timing requirements and potential for irregular bleeding 1, 3
Common Side Effects and Management
Bleeding Irregularities
- Irregular bleeding patterns are the most frequently reported side effect, occurring in up to 25% of users and representing the most common reason for discontinuation 3, 6
- Management of bleeding irregularities may include NSAIDs for 5-7 days of treatment 3
- Counseling about expected bleeding patterns is essential to improve compliance and acceptance 3, 4
Follow-up Requirements
- No routine follow-up visit is required after initiating POPs, but women should be advised to return if they experience side effects or want to change methods 3