Plan B

In 1999, the FDA approved Plan B. It is a two-dose regimen: you take two pills 12 hours apart. Each pill contains 0.75 milligrams of the progestin levonorgestrel.

This is a synthetic hormone that has been used in birth control pills for more than 35 years. But the levels of progestin in Plan B (and Plan B One-Step) are higher than those in birth control pills.

In 2009, the FDA approved Plan B One-Step. It is a one-dose regimen: you take one pill. The pill contains 1.5 milligrams of levonorgestrel. Research has shown that taking Plan B One-Step up to 72 hours after unprotected sex works just as well as Plan B. And it doesn’t cause increased side effects. So Plan B One-Step is replacing Plan B, although it may still be available in some pharmacies and health centers until supplies run out.

Beginning in 2009, Plan B and Plan B One-Step became available without a prescription to women aged 17 and older. But you must show proof of age. They are available by prescription to women younger than age 17.

Depending upon where you are in your cycle, Plan B or Plan B One-Step may work in one of these ways:

• It may prevent or delay ovulation.
• It may interfere with fertilization of an egg.

It is also possible that this type of emergency birth control prevents implantation of a fertilized egg in the uterus by altering its lining.

Plan B or Plan B One-Step is not the same as RU-486, which is an abortion pill. It does not cause a miscarriage or abortion. In other words, it does not stop development of a fetus once the fertilized egg implants in the uterus. So it will not work if you are already pregnant when you take it.

Plan B or Plan B One-Step is more effective than emergency contraceptive pills (ECPs) that contain both estrogen and progestin.

If you take it within 72 hours after you’ve had unprotected sex, Plan B One-Step can reduce the risk of pregnancy by up to 89%. If you take Plan B One-Step within 24 hours, it is about 95% effective.

But you should know that Plan B or Plan B One-Step is not as effective as regular contraception. So don’t take it as your main form of birth control. And, it does not protect you against sexually transmitted diseases. Think of it as a backup — not for routine use. That’s why it’s called Plan B.

Available in drugstores and health centers, Plan B or Plan B One-Step costs from $10 to $70. Because it is most effective when taken as soon as possible, consider having a ready supply in your medicine cabinet. If you are under 17, you will need to talk with your doctor about a prescription.

If you are taking Plan B, take one pill within 72 hours after unprotected sex and another pill 12 hours later.

If you are taking Plan B One-Step, take a single pill as soon as possible but within 72 hours of unprotected sex.

You can take Plan B or Plan B One-Step if:

• You didn’t use any birth control.
• The condom came off or broke.
• The diaphragm slipped out of place.
• You missed at least two or three active birth control pills in a row.
• You forgot to insert your ring or apply your patch.
• Your partner didn’t pull out in time.
• You have another reason to think your birth control might not have worked.
• You were forced to have sex.

Remember: Plan B or Plan B One-Step will not protect you from getting pregnant if you have sex after taking the pills. Instead, you need to take it right after you have unprotected sex.

Do not take Plan B or Plan B One-Step if:

• You know you are pregnant or suspect you might be.
• You have a history of allergy or hypersensitivity to its ingredients.
• You have a history of recent abnormal vaginal bleeding that your doctor has not yet evaluated.

Many women have taken emergency contraception without serious complications. But it’s a good idea to ask your doctor about possible interactions with other medications.

Plan B or Plan B One-Step is considered safe for most women. You should not take it if you are pregnant; at this time, there is limited data on the safety of taking Plan B or Plan B One-Step while pregnant.

Potential side effects of Plan B or Plan B One-Step include:

• nausea
• abdominal pain
• fatigue
• headache
• menstrual changes
• dizziness
• breast tenderness
• vomiting
• diarrhea

Plan B or Plan B One-Step causes less nausea and vomiting than ECPs that contain both estrogen and progestin. And, you may be able to reduce any nausea or vomiting by taking the pill on a full stomach. Eating small, frequent meals over 24 hours may also help.

With Plan B or Plan B One-Step, you may also have some unexpected bleeding. It should go away by the time of your next period. However, it is possible that Plan B or Plan B One-Step may cause your next period to be heavier or lighter than usual. It may also come earlier or later than is normal for you. If you don’t get your period within three weeks, get a pregnancy test to make sure you’re not pregnant.