Mifepristone (RU–486) is:
**Core Concept**
Mifepristone, also known as RU-486, is a synthetic steroid with potent anti-glucocorticoid and anti-progestogenic properties. It acts by competitively inhibiting the glucocorticoid receptor and progesterone receptor, thereby exerting its therapeutic effects.
**Why the Correct Answer is Right**
Mifepristone's mechanism of action involves binding to the progesterone receptor, which is essential for maintaining the pregnancy. By blocking this receptor, mifepristone prevents the maintenance of pregnancy, making it a key component in medical abortion. Additionally, mifepristone has anti-glucocorticoid effects, which can be beneficial in treating Cushing's syndrome. Its anti-progestogenic effects are utilized in the treatment of severe hyperemesis gravidarum and in the management of uterine fibroids.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because mifepristone does not primarily act as a dopamine antagonist. Dopamine antagonists, such as haloperidol, are used to treat schizophrenia and other psychiatric disorders.
**Option B:** This option is incorrect because mifepristone is not an estrogen receptor modulator. Selective estrogen receptor modulators (SERMs) like tamoxifen are used in the treatment of breast cancer.
**Option C:** This option is incorrect because mifepristone is not primarily used as an anabolic steroid. Anabolic steroids are synthetic derivatives of testosterone used to promote muscle growth.
**Clinical Pearl / High-Yield Fact**
Mifepristone is a potent anti-progestogen, and its use in medical abortion requires careful patient selection and follow-up. It's essential for clinicians to be aware of its potential side effects, including nausea, vomiting, and dizziness.
**Correct Answer:** C. A synthetic steroid with potent anti-glucocorticoid and anti-progestogenic properties.