How Do Cortisol Receptor Blockers Work?

Cortisol receptor blockers (synthetic steroids) are a class of drugs used for the medical termination of intrauterine pregnancy during its early phase. Early pregnancy is considered up to week 10 (up to 70 days after the first day of the last menstrual period), and they are used to control hyperglycemia (high blood glucose level) secondary to hypercortisolism (high level of cortisol-a hormone made by the outer layer of the adrenal gland) in adults with endogenous Cushing’s syndrome (a disorder caused by the body's exposure to an excess level of the hormone cortisol) who have type 2 diabetes mellitus or glucose intolerance and have failed surgery or are not eligible for surgery The only drug that belongs to this class is “mifepristone,” an antiprogestational steroid (progesterone antagonists), usually used in combination with another medicine called misoprostol.

Mifepristone is not indicated in a rare abnormal pregnancy that is outside the womb (ectopic pregnancy). It may cause an ectopic pregnancy to rupture, resulting in very serious bleeding.

Cortisol receptor blockers are administered orally, typically a single dose. Vaginal bleeding, cramps, nausea, and diarrhea usually begin within two days after the medication. Vaginal bleeding or spotting usually lasts for 9 to 16 days but can last for 30 days or longer.

Cortisol receptor blockers work in the following ways:

• Work by blocking the activity of progesterone, a natural substance that the body produces to help continue a pregnancy.
• Act as progestational and glucocorticoid hormone antagonist that inhibits progesterone which in turn induces bleeding by releasing endogenous prostaglandins from the endometrium (lining of the uterus) or decidua (modified endometrium that forms in preparation for pregnancy).
• Block the binding of cortisol to its receptor which helps in reducing the effects of excess cortisol, such as high blood sugar levels.

Cortisol receptor blockers are used in conditions such as:

• Pregnancy termination
• Cushing's syndrome (a disorder caused by the body's exposure to an excess level of the hormone cortisol) 
• Ovarian cancer

Some of the common side effects include:

• Diarrhea
• Nausea
• Vomiting
• Myalgia (muscle pain)
• Weakness
• Abdominal pain
• Cramping
• Headache
• Fatigue (overall feeling of tiredness or lack of energy)
• Decreased appetite
• Back pain
• Indigestion
• Leg pain

Other rare side effects include:

• Dizziness (feeling faint, weak, or unsteady)
• Arthralgia (joint pain)
• Hypokalemia (low blood potassium level)
• Allergic reactions such as the closing of the throat, swelling of the lips and tongue, or face
• Insomnia (trouble falling and/or staying asleep)
• Sinusitis (inflammation or swelling of the tissue lining the sinuses)
• Endometrial hypertrophy (thickening of the endometrium [lining of the uterus])
• Hypoglycemia (low blood sugar level)
• Anxiety
• Asthenia (abnormal physical weakness or lack of energy)
• Abnormal thyroid function test
• Fast/irregular heartbeat

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 other medicines. Never stop taking your medication and never change your dose or frequency without consulting your doctor.

Generic and brand names of cortisol receptor blockers include:

• Korlym
• Mifeprex
• Mifepristone
• Ru486