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Drugs reference index «Levonorgestrel»



Brand names: Plan B

Why is Levonorgestrel prescribed?

Plan B is intended as "morning after" birth control to prevent pregnancy after known or suspected contraceptive failure (for instance, a broken condom) or unprotected sex. Plan B treatment must begin within 72 hours after having sex.

Plan B contains only one hormone, a progestin. It may prevent a pregnancy but will not end one that has already begun. It is believed to work mainly by inhibiting ovulation (release of an egg) and fertilization. It may block implantation of the egg in the lining of the uterus. It is not effective once the process of implantation has begun.

Most important fact about Levonorgestrel

Plan B is meant for emergency use only and not as a regular method of birth control. It is not as reliable as regular birth control. Using Plan B correctly after a single act of unprotected sex reduces the average chance of pregnancy to about 1 percent.

How should you take Levonorgestrel?

Plan B comes in a package with two tablets. Take the first tablet as soon as possible after having sex, within 72 hours at the latest. Take the second tablet 12 hours after the first one. You can take Plan B at any time during your menstrual cycle.

  • If you miss a dose...Call your doctor immediately. Your chances of pregnancy increase when you do not take the pills as prescribed.
  • Storage instructions...Store at room temperature.

What side effects may occur?

Side effects cannot be anticipated. If any develop or change in intensity, tell your doctor as soon as possible. Only your doctor can determine if it is safe to continue using Plan B.

  • Side effects may include:Abdominal pain, breast tenderness, diarrhea, dizziness, fatigue, headache, menstrual changes, nausea, vomiting

Why should Levonorgestrel not be prescribed?

Do not take Plan B if you have had an allergic reaction to progestin, the type of hormone found in the drug. You should also avoid Levonorgestrel if you have any unexplained vaginal bleeding.

Special warnings about Levonorgestrel

Remember that Plan B should not be used as a regular form of birth control, and it will not work if you are already pregnant.

Plan B may affect your next menstrual cycle by delaying it or making it much heavier or lighter than normal. It could also cause spotting between cycles. If your next period is delayed by more than a week, you should consider the possibility that you may be pregnant.

Let your doctor know right away if you become pregnant or develop abdominal pain after taking Plan B. There is a slight chance that progestin, the hormone in Plan B, could cause an ectopic pregnancy, which occurs when a fertilized egg becomes implanted outside the uterus, usually in the fallopian tube.

Plan B could slightly raise blood sugar levels. If you have diabetes, your doctor may want to monitor you during treatment.

Emergency contraceptive pills, like other oral contraceptives, do not protect against infection with HIV (the virus that causes AIDS) and other sexually transmitted diseases.

Possible food and drug interactions when taking Levonorgestrel

When Plan B is taken together with other medications, the effectiveness of Plan B may be altered or reduced. Notify your doctor if you are taking the following:

CarbamazepinePhenytoinRifampinSedatives or tranquilizers classified as barbiturates

Special information if you are pregnant or breastfeeding

Contraceptives like Plan B that contain the hormone progestin do not appear to harm a developing baby. However, if you're pregnant or suspect that you're pregnant, you should not take Plan B, since it's not effective after pregnancy has begun.

Although small amounts of progestin can pass into breast milk, no side effects have been identified. Still, it's always best to check with your doctor before breastfeeding during treatment with any medication.

Recommended dosage for Levonorgestrel


Plan B comes in a package with two tablets. Take the first pill as soon as possible after unprotected sex, within 72 hours at the latest. Take the second pill 12 hours after the first one. If you vomit within 1 hour after taking either pill, contact your doctor right away to see if you should take another dose.


If you suspect an overdose, seek medical attention immediately.

  • Symptoms of overdose may include:Nausea, vomiting
  • Levonorgestrel MedFacts Consumer Leaflet (Wolters Kluwer)
  • Levonorgestrel Professional Patient Advice (Wolters Kluwer)
  • levonorgestrel Intrauterine Advanced Consumer (Micromedex) - Includes Dosage Information
  • Mirena Prescribing Information (FDA)
  • Mirena Consumer Overview
  • Mirena IUD MedFacts Consumer Leaflet (Wolters Kluwer)
  • Next Choice Prescribing Information (FDA)
  • Next Choice Oral, Implantation, Parenteral Advanced Consumer (Micromedex) - Includes Dosage Information
  • Plan B Consumer Overview
  • Plan B Prescribing Information (FDA)
  • Plan B One-Step MedFacts Consumer Leaflet (Wolters Kluwer)
  • Plan B One-Step Consumer Overview

See Also...

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