**Question:** Most common side effect of mifepristone

**Core Concept:** Mifepristone is a synthetic glucocorticoid receptor antagonist with anti-progestogenic, anti-androgenic, and anti-glucocorticoid activities. It is primarily used for its ability to induce uterine contractions and cause expulsion of the fetus and placenta following administration of prostaglandin analogs.

**Why the Correct Answer is Right:** The most common side effect of mifepristone is uterine bleeding, also known as menstrual-like bleeding. This occurs due to the drug's anti-progestogenic activity, which blocks the action of progesterone in the uterus. Progesterone is essential for maintaining the endometrium and pregnancy. By blocking progesterone's action, mifepristone triggers a series of events that lead to uterine contractions, resulting in the expulsion of the fetus and placenta. Consequently, the uterus starts to shed its lining, leading to the observed menstrual-like bleeding.

**Why Each Wrong Option is Incorrect:**

A. **Increased lactation (galactorrhea):** Although mifepristone can cause a temporary increase in breast milk production due to its anti-glucocorticoid activity, this is not the most common side effect.

B. **Increased appetite (hyperphagia):** Mifepristone can increase appetite due to its anti-glucocorticoid activity, but this is not the most common side effect.

C. **Low blood pressure:** Mifepristone does not primarily affect blood pressure; its primary effects are related to its actions on the endometrium and the pituitary gland.

D. **Anaphylactic shock:** This is a severe allergic reaction and not a direct side effect of mifepristone administration. Though rare, patients may experience anaphylaxis due to their underlying medical conditions or simultaneous administration of other medications.

**Core Concept:** Mifepristone is primarily a progesterone receptor antagonist, which binds to progesterone receptors and prevents progesterone from binding, thereby inhibiting progesterone's actions. This is particularly useful in inducing uterine contractions and expelling the fetus and placenta during medical termination of pregnancy.

**Why the Correct Answer is Right:**

The most common side effect of mifepristone is uterine bleeding due to its anti-progestogenic activity. By inhibiting the action of progesterone, mifepristone triggers uterine contractions, which result in the expulsion of the fetus and placenta, followed by uterine shedding of the endometrial lining, leading to the observed menstrual-like bleeding.

**Why Each Wrong Option is Incorrect:**

A. **Increased lactation (galactorrhea):** Mifepristone can transiently increase lactation due to its anti-glucocorticoid activity. However, this is not the primary side effect, and uterine bleeding is more common.

B.