What is the mechanism of action of Diltiazem Hydrochloride?

Diltiazem Hydrochloride is a calcium channel blocker that primarily acts on the heart and vascular smooth muscle. Its mechanism of action involves decreasing heart rate and prolonging atrioventricular (AV) nodal conduction. By inhibiting the influx of calcium ions through L-type calcium channels, Diltiazem ultimately reduces the excitability and automaticity of the pacemaker cells in the heart, resulting in a lower heart rate. Additionally, this reduction in calcium influx at the AV node leads to prolonged conduction times, effectively slowing down the overall conduction velocity through this pathway.

This unique effect makes Diltiazem particularly useful in managing conditions like hypertension and certain types of arrhythmias, as it helps control heart rate and improve oxygen delivery to the heart by reducing cardiac workload. The other choices describe mechanisms that do not align with the pharmacological profile of Diltiazem. For instance, increasing heart rate or calcium levels would be counterproductive to the drug’s intended effects, while inhibiting cardiac contractility is not a primary action of Diltiazem but rather a consequence of reducing calcium availability in the heart muscle. Thus, the correct understanding of Diltiazem’s mechanism highlights its role in cardiovascular therapy.