When prescribed for angina, how does oral nifedipine achieve a therapeutic effect?

Nifedipine is a calcium channel blocker that specifically targets the L-type calcium channels present in the smooth muscle of blood vessels and the myocardium. By inhibiting the influx of calcium through these channels, nifedipine causes vasodilation of coronary and peripheral arteries. This leads to a decrease in myocardial oxygen demand, alleviating the symptoms of angina.

In the context of angina, reducing calcium entry into the cells helps to lower the force of contraction of the heart (inotropic effect) and decreases heart rate (chronotropic effect) when taken in certain formulations (like extended-release). This overall reduction in myocardial workload and oxygen consumption is crucial for patients experiencing angina pectoris, where the heart's demand for oxygen exceeds the supply due to narrowed coronary arteries.

The other answer options do not accurately describe the mechanism of action for nifedipine in the treatment of angina, as they pertain to different physiological pathways or agents that do not involve calcium channel modulation.