Levonorgestrel, such as Plan B or Next Choice, is specially packaged for emergency
contraception. You can buy this medicine in most drugstores.
Emergency contraception is used after unprotected sex to
prevent a pregnancy from starting. It is most effective when it is used as soon
as possible after intercourse. It is not necessary to take a pregnancy test
before using emergency contraception.
experts recommend having emergency contraception pills, or a prescription for
them, on hand in case you ever need them.
Emergency contraception is most effective when used as soon as possible after unprotected sex. Your risk of becoming pregnant increases as time
For the emergency contraception option that contains 2 pills, you can take both pills at the same time. Or you can take 1 pill right away and the second pill
12 hours later.
There is also a one-pill emergency contraception option that lets you take the dose you need in just 1 pill.
You can take emergency contraception up to 5 days after
unprotected sex. But it works best if you take it right away.
Emergency contraception pills work by
preventing ovulation, fertilization, or implantation.
contraception hormones may prevent fertilization by stopping the ovary from
releasing an egg (ovum). They also make the fallopian tubes less likely to move
an egg toward the uterus. Emergency contraception is also thought to thin the
lining of the uterus, or
endometrium. The thickened endometrium is where a
fertilized egg would normally implant and grow.
contraception does not protect against
sexually transmitted infections (STIs).
Emergency contraception is meant to
be used as a backup method for preventing pregnancy. For regular protection, be
sure that you have:
You can use emergency contraception if you are not
confident that you were protected against pregnancy during intercourse. This
can happen if:
Be sure to plan with your doctor for your birth control
effectiveness varies according to the method used.
The sooner pills are used after unprotected sex, the more
likely they are to prevent pregnancy.
effects may include the following:
Call your doctor if side effects, such as headache,
dizziness, or belly pain, continue for longer than 1 week after using emergency
See your doctor if you do not have your period within 21
days after using emergency contraception.
See Drug Reference for a full list of side effects.
(Drug Reference is not available in all systems.)
Some pharmacists refuse to fill
emergency contraception prescriptions based on their personal beliefs. If this
happens to you, ask for the location of a pharmacist who will fill the
prescription, or contact:
Emergency contraception use is not
recommended if you know or suspect you are already pregnant. If you may already
be pregnant, see your doctor.
If hormonal emergency contraception does not work and a
pregnancy develops and grows, there is no known risk to the embryo.2
Complete the new medication information form (PDF)(What is a PDF document?) to help you understand this medication.
American College of Obstetricians and Gynecologists (2010). Emergency contraception. ACOG Practice Bulletin No. 112. Obstetrics and Gynecology, 115(5): 1100–1109.
Stewart F, et al. (2007). Emergency contraception. In RA Hatcher et al., eds., Contraceptive Technology, 19th ed., pp. 87–112. New York: Ardent Media.
May 4, 2012
Sarah Marshall, MD - Family Medicine
& Femi Olatunbosun, MB, FRCSC - Obstetrics and Gynecology
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