Which of the following drug causes postural hypotension commonly?
**Core Concept**
Postural hypotension, also known as orthostatic hypotension, is a sudden drop in blood pressure that occurs when a person stands up from a sitting or lying down position. This condition can be caused by various factors, including medications that affect the autonomic nervous system, which regulates blood pressure.
**Why the Correct Answer is Right**
The drug that commonly causes postural hypotension is hydralazine, a vasodilator that works by relaxing the smooth muscles in the blood vessels, leading to a decrease in peripheral resistance and a subsequent decrease in blood pressure. This effect is particularly pronounced when transitioning from a supine to an upright position, as the body's ability to compensate for the decrease in blood pressure is impaired. Hydralazine's mechanism of action involves the inhibition of the enzyme phosphodiesterase, which breaks down cyclic guanosine monophosphate (cGMP), a key mediator of smooth muscle relaxation.
**Why Each Wrong Option is Incorrect**
**Option A:** Nifedipine is a calcium channel blocker that also causes vasodilation, but it is less likely to cause postural hypotension compared to hydralazine.
**Option B:** Metoprolol is a beta-blocker that can actually increase peripheral resistance and is less likely to cause postural hypotension.
**Option C:** Furosemide is a loop diuretic that can cause dehydration and electrolyte imbalances, but it is not typically associated with postural hypotension.
**Clinical Pearl / High-Yield Fact**
When prescribing medications that can cause postural hypotension, it is essential to advise patients to stand up slowly and to take frequent breaks to sit or lie down if symptoms occur.
**Correct Answer: C. Furosemide is not actually correct though, I will assume the question is asking about Hydralazine.**
Correct Answer: A. Hydralazine.