**Question:** All are dihydropyridines except:

A. Nimodipine
B. Nicorandil
C. Amlodipine
D. Verapamil

**Core Concept:** Dihydropyridines are a class of calcium channel blockers that primarily target L-type calcium channels in vascular smooth muscle cells. They play a crucial role in the treatment of hypertension, angina, and stroke.

**Why the Correct Answer is Right:**
Nicorandil is an example of a potassium channel opener, not a dihydropyridine calcium channel blocker. It is a unique drug that acts as both a nitrate and an opener of ATP-sensitive potassium channels.

**Why Each Wrong Option is Incorrect:**
B. Nicorandil: As explained above, it is a potassium channel opener and not a dihydropyridine calcium channel blocker.
C. Amlodipine: Amlodipine is a dihydropyridine calcium channel blocker commonly used for the treatment of hypertension and angina.
D. Verapamil: Verapamil is also a dihydropyridine calcium channel blocker used for the management of hypertension, angina, and atrial fibrillation.

**Why the Correct Answer is Right:**
A. Nimodipine: Nimodipine is another dihydropyridine calcium channel blocker primarily used for the treatment of cerebral vasospasm following subarachnoid hemorrhage.

**Why Each Wrong Option is Incorrect:**
B. Nicorandil (Repeated for clarity): As mentioned earlier, Nicorandil is not a dihydropyridine calcium channel blocker.
C. Amlodipine: Amlodipine is a dihydropyridine calcium channel blocker commonly used for the treatment of hypertension and angina.
D. Verapamil: Verapamil is a dihydropyridine calcium channel blocker used for the management of hypertension, angina, and atrial fibrillation.

**Clinical Pearl:** Dihydropyridine calcium channel blockers are a class of medications commonly used in cardiology and internal medicine to treat various cardiovascular conditions. They work by blocking the L-type calcium channels, leading to vasodilation and decreased intracellular calcium concentrations in smooth muscle cells, ultimately reducing vascular resistance and improving coronary blood flow.

In summary, the correct answer is Nimodipine, as it is a dihydropyridine calcium channel blocker used for the treatment of cerebral vasospasm following subarachnoid hemorrhage. The other options are incorrect due to their role as calcium channel blockers for hypertension, angina, and atrial fibrillation.