Progestin-only hormonal methods (mini-pills, shots)

Examples

Oral contraception

Generic Name	Brand Name
progestin-only pills	Micronor

Shot

Generic Name	Brand Name
medroxyprogesterone acetate	Depo-Provera

How It Works

Progestin-only birth control methods, including pills (called "mini-pills") and shots, prevent the ovaries from releasing an egg (ovulation), thicken mucus at the cervix so sperm cannot enter the uterus, and in rare cases, prevent a fertilized egg from implanting in the uterus.

Birth control mini-pills

Progestin-only mini-pills come in a monthly pack. To be effective, the pills must be taken at the same time each day.

• If you take a pill more than 3 hours late, use another method of birth control for the next 48 hours to prevent pregnancy. Consider using emergency contraception if you have had sex in the past 3 to 5 days.¹
• If you forget to take a pill for even one day, you must use a second method of birth control until your next period to prevent pregnancy.² You can't take extra mini-pills (as with combination pills) to make up for a missed day.

Shots

One injection of Depo-Provera is effective for 12 to 13 weeks.

Why It Is Used

Progestin-only mini-pills and shots are good choices for women who:

• Are breast-feeding. The mini-pill is a good choice for breast-feeding mothers. It is very low-dose and does not affect the milk supply. Breast-feeding further reduces the chance of pregnancy.
• Need short- or long-term birth control that can be stopped at any time. (However, it may take from 12 weeks to 18 months to become pregnant after a Depo-Provera injection.)
• Prefer a form of birth control that does not interfere with sexual spontaneity.
• Cannot take estrogen, including those who smoke and are older than 35; have long-standing, poorly controlled diabetes; have heart disease; have problems with blood clots; or have high blood pressure.
• Have migraine headaches with auras, or women whose migraines get worse when taking the estrogen in combination birth control pills.
• Have heavy, painful menstrual periods. Progestin reduces heavy bleeding and cramping.
• Have anemia from heavy menstrual bleeding.

How Well It Works

Shots are highly effective methods of birth control.

Progestin-only mini-pills are very effective, but combination hormone pills are even more effective. Also, the mini-pill has to be taken at the same time every day to work correctly.

Depo-Provera shot

This method is highly effective, unless you fail to get a shot after 3 months.³

• Typical use: Among all Depo-Provera users, 3 women in 100 become pregnant per year.
• Perfect use: Of women who get their shots on schedule, only 3 in 1,000 become pregnant per year.

Progestin mini-pill

This method is very effective, but you must take the mini-pill at the same time every day.³

• Typical use: Among all mini-pill users, 8 women in 100 become pregnant per year.
• Perfect use: Of women who take every mini-pill on schedule, only 3 in 1,000 become pregnant per year.

Medications that can interfere with hormonal birth control

Some medications make the liver clear more medication from your blood than normal. When a medication lowers your blood level of birth control hormones, you are more likely to become pregnant.

• The shot is only less effective when taken with nevirapine (Viramune), which some people take for Cushing's disease.⁴
• The mini-pill is less effective when it is taken with some anticonvulsants, including carbamazepine (Tegretol), phenobarbital, phenytoin (Dilantin), and primidone. The antibiotic rifampin (Rifadin), the antifungal griseofulvin (Fulvicin), and the herb St. John's wort also have this effect, increasing your chances of pregnancy.^{4, 5} If you are taking one of these medications, use Depo-Provera injections or another birth control method.

Side Effects

Most side effects of the progestin-only birth control methods go away after the first few months of use. Side effects include:

• Irregular menstrual cycles.
• Spotting or bleeding between menstrual periods.
• Sore breasts.
• Headache.
• Nausea.
• Dizziness.
• Bloating or weight gain, especially with the Depo-Provera shot (to manage this, increase your activity level).^{4, 1}
• No menstrual periods. Although mini-pill use can stop periods, the shot is most likely to do so. After 1 year of taking Depo-Provera shots, 25% of women stop having monthly periods. After 5 years of shots, 80% of women do not have periods.⁴ This does not cause medical problems.

Less common progestin side effects include depression and darkening of the skin on the upper lip, under the eyes, or on the forehead (chloasma).

Depo-Provera risks

Bone thinning. Depo-Provera use for 2 or more years can cause bone loss, which may not be fully reversible after stopping the medication.⁶ Bone loss can lead to osteoporosis in later life, which makes bones weak enough that they are more likely to break.

For teens, bone loss from Depo-Provera is a big concern. Teens are normally building bone mass as they grow. This is why it is very important for teens to get enough calcium and vitamin D when using Depo-Provera. A small study among teens showed that bone loss from Depo-Provera was reversed after the teens stopped getting the shots.⁷ Talk to your doctor about your risk if you have been using Depo-Provera for longer than 2 years.

Infection risk. One recent study has shown that Depo-Provera use may make chlamydia or gonorrhea infection more likely if you are exposed to these bacteria.⁸ If you have any risk of being exposed to sexually transmitted diseases, use condoms.

Progestin risk after having gestational diabetes

Breast-feeding women can use the mini-pill or shot without worrying about effects on their milk supply or the baby. However, using progestin-only birth control after having gestational diabetes appears to make it more likely that you will develop diabetes.^{9, 10} (Combination estrogen-progestin birth control does not appear to increase this diabetes risk.⁵)

See Drug Reference for a full list of side effects. (Drug Reference is not available in all systems.)

What To Think About

Progestin-only mini-pills may not be as effective if you are vomiting or have diarrhea. Use another method of birth control for 7 days after vomiting or diarrhea, even if you have not missed any pills.

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Author:	Merrill Hayden Carrie Henley	Last Updated: August 16, 2006
Medical Review:	Adam Husney, MD - Family Medicine Joy Melnikow, MD, MPH - Family Medicine Kirtly Jones, MD - Obstetrics and Gynecology Femi Olatunbosun, MB, FRCSC - Obstetrics, Gynecology and Reproductive Medicine
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