Which one of the following is a relatively selective α2 adrenergic blocker with short duration of action ?
**Core Concept**
α2 adrenergic blockers are a class of medications used to treat conditions such as hypertension, glaucoma, and erectile dysfunction by inhibiting the action of α2 adrenergic receptors. These receptors are located in the brain and peripheral nervous system, and their activation can lead to decreased sympathetic tone and decreased blood pressure.
**Why the Correct Answer is Right**
Yohimbine is a relatively selective α2 adrenergic blocker with a short duration of action. It works by competing with endogenous norepinephrine for binding sites on α2 adrenergic receptors, thereby preventing the inhibitory effects of norepinephrine on neurotransmitter release. This results in increased sympathetic tone and increased blood pressure. Yohimbine's short duration of action is due to its rapid metabolism and excretion.
**Why Each Wrong Option is Incorrect**
**Option A:** Prazosin is a non-selective α1 adrenergic blocker, primarily used to treat hypertension and benign prostatic hyperplasia. It is not a selective α2 adrenergic blocker and has a longer duration of action compared to yohimbine.
**Option C:** Terazosin is another non-selective α1 adrenergic blocker, used to treat hypertension and benign prostatic hyperplasia. Like prazosin, it is not a selective α2 adrenergic blocker and has a longer duration of action compared to yohimbine.
**Option D:** Doxazosin is a non-selective α1 adrenergic blocker, primarily used to treat hypertension and benign prostatic hyperplasia. It is not a selective α2 adrenergic blocker and has a longer duration of action compared to yohimbine.
**Clinical Pearl / High-Yield Fact**
Yohimbine is also known for its ability to increase libido and is sometimes used off-label to treat erectile dysfunction. However, its use is not without risks, as it can cause tachycardia, hypertension, and anxiety in some individuals.
**✓ Correct Answer: B. Yohimbine**