Which of the following is an active metabolite of another drug and is available as a separate drug for the treatment of angine?
**Core Concept**
The question is testing the concept of drug metabolism and the availability of active metabolites as separate drugs for therapeutic use. In pharmacology, an active metabolite is a metabolite that retains the pharmacological activity of the parent compound.
**Why the Correct Answer is Right**
The correct answer is a well-known active metabolite of another drug, which is available as a separate medication for the treatment of angina. This active metabolite is produced through the hepatic metabolism of its parent compound, a beta-blocker. The resulting active metabolite has a longer half-life and is more lipophilic, allowing it to more effectively inhibit the beta-1 adrenergic receptors in the heart, leading to a reduction in heart rate and contractility. This results in decreased myocardial oxygen demand, thereby alleviating angina symptoms.
**Why Each Wrong Option is Incorrect**
* **Option A:** This is not an active metabolite of a beta-blocker and is not used for the treatment of angina.
* **Option B:** This option is not a recognized active metabolite of a beta-blocker, and its use in treating angina is not established.
* **Option D:** This is not an active metabolite of a beta-blocker and is not used for the treatment of angina.
**Clinical Pearl / High-Yield Fact**
It's essential to remember that active metabolites can have different pharmacokinetic properties and therapeutic effects compared to their parent compounds. This is crucial in clinical practice, as it may impact dosing regimens and the choice of treatment.
**Correct Answer:** C. Nitroglycerin (active metabolite of pentaerythritol tetranitrate)