(Updated June 2014)
Two formulations are available: one contains 0.35 mg of norethindrone, the other contains 0.075 mg of norgestrel. The primary mechanism of action is thickening of the cervical mucus.
The efficacy of progestin-only pills is highly dependent on consistent use; it is critical that women take the pill at the same time (i.e., within 3 hours) every day. There is no placebo week with progestin-only pills.
Often called “mini-pills,” progestin-only pills are a good contraceptive choice for women who cannot use estrogen.58
This method is highly effective, with a failure rate of 0.3 percent with perfect use and 9 percent with typical use.19
- The primary side effect of progestin-only oral contraceptives is irregular menstrual bleeding—spotting or breakthrough bleeding, amenorrhea, or shortened cycles.
- Irregular bleeding decreases in many users by cycle 12.
- Less common side effects include headache, breast tenderness, and dizziness.
Contraindications and Precautions
|Medical Eligibility Criteria for Progestin-only Pills|
(unacceptable health risk if the contraceptive method is used)
(theoretical or proven risks usually outweigh the advantages of using the method)
Source: Reference 5
- Rapidly reversible
- Easy to use, start, and stop
- No associated nausea
- Lack of estrogen in progestin-only pills makes the method appropriate for smokers older than age 35, postpartum breastfeeding women, and others with contraindications to estrogen
- Provides protection against uterine and ovarian cancer, benign breast disease, PID
- Requires a prescription
- Adherence can be challenging; user must remember to take pill at same time daily
- Initial irregular bleeding
- No protection against STIs
- The progestin-only pill must be taken at the same time each day.
- If a pill is more than 3 hours late, a back-up method of contraception should be used for at least the next 48 hours.
- Patients using progestin-only pills should obtain emergency contraception in advance. (Note that patients who are less than 17 years old will need a prescription for EC.)
- A range of bleeding disturbances may occur with progestin-only pills—from amenorrhea to irregular, frequent, or prolonged bleeding.
- The irregular bleeding pattern is likely to improve within a few months of pill initiation.
- If bleeding is heavy or particularly bothersome, women should contact their health care provider.
- This method does not protect against STIs.
About Audrey Kelly, PharmD