How Do Antiprogestins Work?

Antiprogestins are medications administered to terminate intrauterine pregnancy in its early phase, up to 10 weeks of gestation. Antiprogestins are also used to manage and treat high blood glucose levels (hyperglycemia) in people with Cushing’s syndrome, a disorder that leads to excessive levels of cortisol, a natural steroid hormone.

Antiprogestins are synthetic steroids that work in the following ways:

• Block the activity of progesterone, a natural hormone that prepares the endometrium, the inner lining of the uterus, for implantation and continuation of pregnancy.
• Increase the concentration of prostaglandin, a natural compound in the body that promotes contraction of the uterine muscle wall (myometrium), which results in menstrual bleeding and termination of pregnancy.
• Block cortisol from binding to its glucocorticoid receptors, mitigating hyperglycemia caused by excess cortisol levels. Antiprogestins, however, do not reduce cortisol levels.

Antiprogestins are administered orally as tablets, and are approved by the FDA for use in the following conditions:

• Pregnancy termination up to 10 weeks of gestation, in combination with misoprostol, a drug that induces uterus contraction. Antiprogestin is typically administered as a single dose followed by misoprostol 24-48 hours later.
• Management and treatment of hyperglycemia secondary to hypercortisolism in adults with endogenous Cushing’s syndrome who have type 2 diabetes mellitus or glucose intolerance and have failed surgery or cannot have surgery.
• Ovarian cancer (orphan designation)

Side effects of antiprogestins may include the following:

• Abdominal pain, cramping
• Uterine cramping
• Nausea
• Vomiting
• Diarrhea
• Headache
• Dizziness
• Fatigue
• Endometrial hypertrophy
• Hypokalemia (low potassium level in the blood)
• Arthralgia (joint pain)
• Peripheral edema
• Hypertension (high blood pressure)
• Decreased appetite
• Abnormal thyroid function test result
• Xerostomia (dry mouth)
• Back pain
• Dyspnea (shortness of breath)
• Myalgia (muscle pain)
• Pain
• Sinusitis (inflammation of the sinuses)
• Nasopharyngitis (inflammation of nose and throat)
• Pain in the extremities
• Leg pain
• Angioedema (swelling in the tissue under the skin or mucous membranes)
• Pitting edema
• Decrease in hemoglobin
• Anemia
• Uterine hemorrhage
• Viral infection
• Dyspepsia (indigestion)
• Insomnia
• Rigors (chills/shivering)
• Vaginitis (inflammation of the vagina)
• Anxiety
• Fainting
• Leukorrhea (whitish vaginal discharge)
• Pelvic pain
• Asthenia (weakness)
• Constipation
• Somnolence (drowsiness)
• Anorexia (loss of appetite)
• Gastroesophageal reflux disease (GERD)
• Increase in triglycerides
• Hypoglycemia (low blood sugar levels)
• Vaginal hemorrhage, metrorrhagia (vaginal bleeding between periods)
• Malaise
• Thirst
• Muscular weakness
• Flank pain
• Musculoskeletal chest pain
• Adrenal insufficiency
• Rash
• Pruritus (itching)

Information contained herein is not intended to cover all possible side effects, precautions, warnings, drug interactions, allergic reactions, or adverse effects. Check with your doctor or pharmacist to make sure these drugs do not cause any harm when you take them along with travel medicines. Never stop taking your medication and never change your dose or frequency without consulting your doctor.

Generic and brand names of antiprogestin drugs include:

• Korlym
• Mifeprex
• mifepristone
• ru486