Anti Spasmodic effect is seen with –
**Core Concept**
The question is testing the understanding of the mechanism of antispasmodic action in smooth muscle relaxation. Antispasmodic agents work by inhibiting the contraction of smooth muscle cells, which is mediated by the influx of calcium ions into the cell. This is achieved through the blockade of voltage-gated calcium channels.
**Why the Correct Answer is Right**
The correct answer is a calcium channel blocker, such as diltiazem or verapamil, which inhibits the influx of calcium ions into smooth muscle cells, leading to relaxation and antispasmodic effect. This action is mediated through the blockade of L-type calcium channels, which are responsible for the contraction of smooth muscle cells. By blocking these channels, calcium channel blockers reduce the intracellular calcium concentration, leading to muscle relaxation.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because anticholinergics, such as atropine, actually increase the contraction of smooth muscle by blocking muscarinic receptors, which are responsible for the relaxation of smooth muscle. This is the opposite of the desired antispasmodic effect.
**Option B:** This option is incorrect because beta-2 agonists, such as salbutamol, actually cause relaxation of smooth muscle by stimulating beta-2 adrenergic receptors, which leads to the relaxation of smooth muscle. However, this is not the mechanism of antispasmodic action.
**Option D:** This option is incorrect because antihistamines, such as diphenhydramine, do not have a direct effect on smooth muscle contraction and are not typically used as antispasmodics.
**Clinical Pearl / High-Yield Fact**
Calcium channel blockers are often used in the treatment of hypertension, angina, and certain types of arrhythmias, in addition to their antispasmodic effect.
**Correct Answer: C. Calcium channel blockers.**