Following is a specific antidote for poisoning due to metoprolol:
**Core Concept**
Metoprolol, a beta-blocker, is a medication used to treat hypertension, angina, and heart failure. In the event of metoprolol overdose, a specific antidote is required to reverse its effects and prevent severe complications.
**Why the Correct Answer is Right**
The correct antidote for metoprolol poisoning is glucagon, which works by activating protein kinase A (PKA) and increasing cAMP levels, thereby countering the beta-adrenergic blockade caused by metoprolol. This leads to increased heart rate, blood pressure, and contractility, ultimately reversing the effects of the overdose. Glucagon's mechanism of action is distinct from that of epinephrine, which is often used in beta-blocker overdose but can have unpredictable effects due to its ability to stimulate beta-2 receptors.
**Why Each Wrong Option is Incorrect**
**Option A:** Atropine is an anticholinergic agent that can increase heart rate but does not directly counteract the beta-blockade caused by metoprolol.
**Option B:** Epinephrine can be used in beta-blocker overdose but is not the preferred antidote for metoprolol, as it can stimulate beta-2 receptors and cause unwanted effects.
**Option C:** Adrenaline does not directly counteract the beta-blockade caused by metoprolol.
**Clinical Pearl / High-Yield Fact**
Glucagon is a specific antidote for beta-blocker poisoning, and its use should be considered in cases of metoprolol overdose to rapidly reverse cardiac effects and prevent severe complications.
**Correct Answer:** C. Glucagon