Concomitant administration of this drug with organic nitrates is contraindicated due to marked potentiation of vasodilatory action leading to profund hypotension. This drug is:
**Core Concept**
The question tests the understanding of a pharmacological interaction between a vasodilator and organic nitrates, leading to a significant risk of profound hypotension. This interaction is crucial in clinical practice, particularly in the management of cardiovascular diseases.
**Why the Correct Answer is Right**
The correct answer is a phosphodiesterase type 5 (PDE5) inhibitor, which is a well-known potent vasodilator. When administered concomitantly with organic nitrates, the combination can lead to a marked potentiation of vasodilatory action, causing a significant decrease in blood pressure. This is due to the additive effect of nitric oxide-mediated vasodilation and the inhibition of PDE5, leading to increased levels of cyclic guanosine monophosphate (cGMP) and subsequent smooth muscle relaxation.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because while other vasodilators may also interact with organic nitrates, they are not as potent as PDE5 inhibitors in causing profound hypotension.
* **Option B:** This option is incorrect because beta-blockers are actually used to counteract the effects of vasodilators and nitrates, rather than exacerbating them.
* **Option C:** This option is incorrect because calcium channel blockers, while also vasodilators, do not have the same level of interaction with organic nitrates as PDE5 inhibitors.
**Clinical Pearl / High-Yield Fact**
When prescribing PDE5 inhibitors, it is essential to inform patients about the contraindication of concomitant use with organic nitrates, as this can lead to a significant increase in the risk of hypotension.
**Correct Answer: C. Sildenafil**