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What Is an Abortifacient?

An abortifacient is a medicine or substance that causes an established pregnancy to end. In modern clinical care, the term commonly refers to medicines used for medication abortion, particularly mifepristone and misoprostol. Mifepristone blocks progesterone support for the pregnancy, while misoprostol softens the cervix and causes uterine contractions. These medicines are used in evidence-based regimens with instructions for follow-up and access to medical care.

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What Is an Abortifacient?

An abortifacient is a medicine or substance that causes an established pregnancy to end. In modern clinical care, the term commonly refers to medicines used for medication abortion, particularly mifepristone and misoprostol. Mifepristone blocks progesterone support for the pregnancy, while misoprostol softens the cervix and causes uterine contractions. These medicines are used in evidence-based regimens with instructions for follow-up and access to medical care.

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What Are Abortifacients Used For?

Abortifacient medicines are used to end an intrauterine pregnancy through medication rather than a procedure. Some of the same medicines are also used in clinical management after miscarriage or fetal loss. The recommended drug, dose, route, and timing depend on pregnancy duration, medical history, and the clinical situation. A proper assessment also considers the possibility of ectopic pregnancy, which medication abortion does not treat.

How Do Medication Abortions Work?

Mifepristone blocks progesterone, a hormone needed to maintain the uterine lining during pregnancy. Misoprostol then causes the cervix to soften and the uterus to contract, leading to cramping and bleeding as the pregnancy tissue passes. A combined mifepristone and misoprostol regimen is commonly used because it is more effective than misoprostol alone in many settings. Misoprostol-only regimens are also used when mifepristone is unavailable or unsuitable.

How Are Abortifacient Medicines Taken?

Mifepristone is taken by mouth, followed by misoprostol according to the prescribed interval and route. Misoprostol can be given through the cheek, under the tongue, vaginally, or by another recommended route depending on the regimen. Cramping, bleeding, nausea, chills, diarrhea, and temporary fever can occur as the medicines work. Clear instructions should explain expected symptoms, follow-up, and where to seek urgent care.

What Are the Risks and Medical Considerations?

Most medication abortions are completed without serious complications when an appropriate regimen is used, but heavy bleeding, infection, an ongoing pregnancy, or incomplete passage can occur. The medicines do not treat ectopic pregnancy, so severe one-sided pain, shoulder pain, fainting, or dizziness requires urgent assessment. Very heavy bleeding, persistent fever, severe pain, or feeling seriously unwell also needs prompt medical care. Certain bleeding disorders, long-term corticosteroid therapy, adrenal failure, allergy, or other conditions can change whether a regimen is suitable. Follow-up can confirm that the pregnancy has ended and identify complications.

Frequently Asked Questions About Abortifacients

Is emergency contraception an abortifacient?

No. Emergency contraception works mainly by preventing or delaying ovulation and does not end an established pregnancy. Medication abortion is used after pregnancy has begun.

Are mifepristone and misoprostol the same medicine?

No. Mifepristone blocks progesterone, while misoprostol causes cervical changes and uterine contractions. They are commonly used together because their actions complement each other.

Can medication abortion treat an ectopic pregnancy?

No. An ectopic pregnancy is located outside the uterus and requires separate medical evaluation and treatment. Delayed care can lead to life-threatening internal bleeding.

When is urgent medical care needed?

Urgent medical care is needed for very heavy bleeding, fainting, severe or one-sided abdominal pain, shoulder pain, persistent fever, breathing difficulty, or feeling seriously unwell. Patients should follow the emergency instructions provided with their medication or by their clinician.

References

Questions and Answers on Mifepristone for Medical Termination of Pregnancy Through Ten Weeks Gestation. U.S. Food and Drug Administration. https://www.fda.gov/drugs/postmarket-drug-safety-information-patients-and-providers/questions-and-answers-mifepristone-medical-termination-pregnancy-through-ten-weeks-gestation. Date Accessed August 5, 2026.

Mifepristone (Mifeprex): MedlinePlus Drug Information. MedlinePlus. https://medlineplus.gov/druginfo/meds/a600042.html. Date Accessed August 5, 2026.

MIFEPREX (Mifepristone) Tablets Prescribing Information. U.S. Food and Drug Administration. https://www.accessdata.fda.gov/drugsatfda_docs/label/2023/020687Orig1s026lbl.pdf. Date Accessed August 5, 2026.

Abortion Care Guideline, Second Edition. World Health Organization. https://www.who.int/publications/i/item/9789240039483. Date Accessed August 5, 2026.

Plan B One-Step (1.5 mg Levonorgestrel) Information. U.S. Food and Drug Administration. https://www.fda.gov/drugs/postmarket-drug-safety-information-patients-and-providers/plan-b-one-step-15-mg-levonorgestrel-information. Date Accessed August 5, 2026.