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Preven EC

Generic name: ethinyl estradiol and levonorgestrel
Drug class: Contraceptives

Medically reviewed by Last updated on Jun 18, 2021.

What is Preven EC?

Preven EC contains a combination of ethinyl estradiol and levonorgestrel. Ethinyl estradiol and levonorgestrel are forms of estrogen and progesterone, which are both female hormones involved in conception.

Preven EC is used as an emergency contraceptive (EC) to prevent pregnancy after contraceptive failure or unprotected intercourse. Preven EC prevents ovulation (the release of an egg from an ovary), disrupt fertilization (joining of the egg and sperm), and inhibit implantation (attachment of a fertilized egg to the uterus).


The first dose of Preven EC must be taken as soon as possible and within 72 hours of having unprotected sex, and the second dose 12 hours following the first, to be effective.

Preven EC does not protect you from sexually transmitted diseases--including HIV and AIDS.

Before using Preven EC

Before taking Preven EC, tell your doctor if you

  • have high blood pressure, angina, or heart disease;
  • have had a stroke;
  • have a bleeding or blood-clotting disorder;
  • have breast, uterine, or another hormone-related cancer;
  • have liver disease;
  • have undiagnosed, abnormal vaginal bleeding;
  • have migraines or severe, recurrent headaches;
  • have diabetes; or
  • smoke.

You may not be able to take Preven EC, or you may require special monitoring during treatment if you have any of the conditions listed above. Preven EC should not be used at any time during pregnancy except in an attempt to prevent pregnancy within 72 hours following unprotected sexual intercourse. Ethinyl estradiol and levonorgestrel pass into breast milk and may affect milk production. Do not take Preven EC without first talking to your doctor if you are breast-feeding a baby.

How should I take Preven EC?

Take Preven EC exactly as directed by your doctor. If you do not understand these directions, ask your pharmacist, nurse, or doctor to explain them to you.Read the entire patient information book before using the ethinyl estradiol and levonorgestrel emergency contraceptive kit.

Use the pregnancy test provided to determine if you are already pregnant from sex earlier in the month or in a previous month. Preven EC will not be effective if you are already pregnant.

To use the pregnancy test:

  • Remove the test stick from the foil wrapper and take off the protective cap covering the absorbent tip. Hold the test stick with the absorbent tip pointing downward and place the tip into your urine stream for at least five seconds so that the entire tip is wet.
  • Do not urinate on the windows of the test stick.
  • Remove the test stick from your urine stream and lay the test stick on a flat surface with the windows facing up. Wait at least three minutes after exposure to your urine, but not more than 20 minutes, for the results. The test is ready to be read when you see a pink/purple line in the square control window. You must see a line in the square control window in order for the test to be valid. Contact your doctor if you do not see the pink/purple line in the square control window.

If a pink/purple line appears in the round window, you are pregnant. Do not take Preven EC, it will not work. Contact your doctor immediately. The test may show that you are pregnant when you are not if you have had a miscarriage or have given birth within the past 8 weeks. Ask your doctor for help in interpreting the test if you have recently been pregnant.

If no pink/purple line appears in the round window, the test is negative and you are not pregnant. Take two Preven EC tablets as soon as possible and within 72 hours of having unprotected sex. Take the second dose of two tablets 12 hours after the first dose.

The first dose of Preven EC must be taken as soon as possible and within 72 hours of having unprotected sex, and the second dose 12 hours following the first, to be effective.

If you vomit within one hour of taking either dose of Preven EC, contact your doctor.

Schedule a follow-up visit with your doctor for three weeks after taking Preven EC.

Contact your doctor as soon as possible if you miss your period following the use of Preven EC.

Preven EC is not intended for use as ongoing pregnancy protection and should not be used as a routine form of contraception.

Store Preven EC at room temperature away from moisture and heat.

What happens if I miss a dose?

Contact your doctor if you miss a dose of Preven EC. Missing a dose of Preven EC increases the risk of becoming pregnant. It is very important to take the two doses of pills 12 hours apart.

What happens if I overdose?

Death or serious side effects are not likely to occur from an overdose of Preven EC. Consult your doctor, an emergency room, or a poison control center for advice.

Symptoms of an overdose of Preven EC include nausea, vomiting, and menstrual bleeding.

What should I avoid?

Preven EC does not protect you from sexually transmitted diseases--including HIV and AIDS.

Avoid smoking. Smoking increases your risk of developing a heart attack, stroke, or blood clot while taking Preven EC.

Preven EC side effects

If you experience any of the following serious side effects, stop taking Preven EC and seek emergency medical attention:

  • an allergic reaction (difficulty breathing; closing of your throat; swelling of your lips, tongue, or face; or hives);
  • sudden shortness of breath, sudden pain or heaviness in the chest, or coughing up blood (possible heart attack or blood clot in the lung);
  • pain, redness, swelling, or numbness of an arm or leg (possible blood clot in an arm or leg);
  • severe headache, sudden difficulty seeing or speaking, dizziness, weakness, numbness, or fainting;
  • severe pain or tenderness in the stomach area; or
  • liver damage (yellowing of the skin or eyes, nausea, abdominal pain or discomfort, unusual bleeding or bruising, severe fatigue).

Other, less serious Preven EC side effects may be more likely to occur. Continue to take Preven EC and talk to your doctor if you experience

  • headache or mild dizziness;
  • nausea or vomiting;
  • changes in menstrual bleeding (spotting, earlier or later menstrual period, heavier or lighter menstrual bleeding, longer or shorter menstrual period); or
  • breast tenderness.

Side effects other than those listed here may also occur. Talk to your doctor about any side effect that seems unusual or that is especially bothersome.

What other drugs will affect Preven EC?

Some drugs may decrease the effectiveness of Preven EC, which may result in pregnancy. Before taking Preven EC, talk to your doctor if you are taking any of the following medicines:

  • a penicillin antibiotic such as amoxicillin (Amoxil, Trimox, Augmentin, others), penicillin (Veetids, Pen Vee K, Bicillin, Permapen, others), ampicillin (Principen, Omnipen, Totacillin, others), bacampicillin (Spectrobid), carbenicillin (Geocillin), cloxacillin (Cloxapen, Tegopen), dicloxacillin (Dynapen, Dycill, others), nafcillin (Unipen, others), or oxacillin (Bactocill, others);
  • a tetracycline antibiotic such as demeclocycline (Declomycin), doxycycline (Doryx, Doxy, Vibramycin, Vibra-Tabs, others), minocycline (Minocin), or tetracycline (Sumycin, Achromycin, Robitet, Panmycin, others);
  • a barbiturate such as amobarbital (Amytal), butabarbital (Butisol), mephobarbital (Mebaral), secobarbital (Seconal), or phenobarbital (Luminal, Solfoton);
  • a seizure or pain medicine such as phenytoin (Dilantin), primidone (Mysoline), ethosuximide (Zarontin), carbamazepine (Tegretol), and others; or
  • rifampin (Rifadin).

You may require a dosage adjustment or special monitoring during treatment if you are taking any of the medicines listed above.

Drugs other than those listed here may also interact with Preven EC. Talk to your doctor and pharmacist before taking any prescription or over-the-counter medicines.

Further information

  • Your pharmacist has additional information about Preven EC written for health professionals that you may read.

What does my medication look like?

Preven EC is available with a prescription under the brand name Preven Emergency Contraceptive Kit (or Preven EC). Other brand name or generic formulations may also be available. Ask your pharmacist any questions you have about this medication, especially if it is new to you.

Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use this medication only for the indication prescribed.

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.