Which of the following drugs is both aeriolar and venodilator?
**Core Concept**
Nitric oxide (NO) and certain vasodilators can cause both arteriolar and venous dilation due to their effects on vascular smooth muscle. This phenomenon is mediated by the relaxation of smooth muscle cells in both arterioles and venules, leading to decreased vascular resistance and increased venous capacitance.
**Why the Correct Answer is Right**
The correct answer is Nitrates. Nitrates, such as nitroglycerin, release nitric oxide (NO) in the body, which activates guanylyl cyclase in vascular smooth muscle cells. This leads to an increase in cyclic guanosine monophosphate (cGMP) levels, causing smooth muscle relaxation and subsequent arteriolar and venous dilation. This effect is particularly beneficial in conditions like angina pectoris, where reduced blood flow to the myocardium is a major concern.
**Why Each Wrong Option is Incorrect**
**Option A:** Isosorbide mononitrate is a nitrate, but it is primarily an arteriolar dilator, with minimal effect on venous capacitance.
**Option B:** Hydralazine is an arteriolar dilator that acts on the endothelium-independent pathway, primarily affecting arterioles and not causing significant venodilation.
**Option C:** Calcium channel blockers (CCBs) can cause venodilation, but they are not as potent in this regard as nitrates. Additionally, CCBs primarily act on cardiac muscle, reducing contractility and heart rate.
**Clinical Pearl / High-Yield Fact**
Nitrates are contraindicated in patients with hypotension, as they can further decrease blood pressure and reduce cardiac output.
**Correct Answer: C. Nitrates. Nitrates are both arteriolar and venodilators due to their release of nitric oxide, which activates guanylyl cyclase and leads to smooth muscle relaxation in both arterioles and venules.**