Progestin-Only Birth Control Pill Options
The two progestin-only pills (POPs) currently available in the United States are norethindrone (or norgestrel) and drospirenone, both of which can be started anytime without requiring a prior examination. 1
Available Formulations
Norethindrone/Norgestrel POPs
- Brand names: Micronor, Ovrette 2
- Dosing: Norgestrel 75 mcg daily 3, 4
- Backup contraception needed: If started >5 days after menses began, use barrier methods for 2 days 1
- No examination required before initiation 1
Drospirenone POP
- Newer formulation with different backup contraception requirements 1
- Backup contraception needed: If started >1 day after menses began, use barrier methods for 7 days 1
- No examination required before initiation 1
Key Practical Considerations
Effectiveness
- Typical use failure rate: Approximately 9 pregnancies per 100 women in the first year 5
- Mechanism: Works primarily by thickening cervical mucus; may not always inhibit ovulation 5
- Missed pill tolerance: Recent evidence suggests norgestrel POPs maintain contraceptive protection even with a 6-hour delay or one missed pill 4
Common Side Effects
Irregular bleeding is the most significant issue:
- Approximately 40% of women experience vaginal bleeding/spotting 6
- About 25% discontinue due to bleeding patterns 6
- One-fifth of cycles may be shorter than 17 days 3
Management of breakthrough bleeding:
- Adding norethindrone acetate 5 mg significantly reduces bleeding frequency and quantity at 2,4, and 6 weeks compared to doubling the POP dose or switching formulations 6
- Enhanced counseling about expected bleeding patterns reduces discontinuation 5
- If bleeding persists and is unacceptable, consider alternative contraceptive methods 5
Special Populations
Breastfeeding women:
- POPs are widely used and well-tolerated during lactation 7
- No adverse effects on milk production, neonatal growth, or early development 7
- Can be started as early as 1 month postpartum 1
Women with thrombotic risk (antiphospholipid antibodies, SLE):
- POPs are strongly recommended over combined hormonal contraceptives 1
- No increased VTE risk with progestin-only pills (RR 0.90,95% CI 0.57-1.45) 1
- Avoid DMPA in antiphospholipid antibody-positive patients due to thrombogenicity concerns 1
Drug interactions:
- Certain anticonvulsants (phenytoin, carbamazepine, barbiturates, topiramate, oxcarbazepine) reduce effectiveness 1
- Rifampin or rifabutin therapy reduces effectiveness 1
- St. John's wort may reduce effectiveness 1