What are the primary indications for calcium channel blockers?

Calcium channel blockers are primarily indicated for conditions involving complications related to the cardiovascular system, particularly angina and hypertension. They function by inhibiting calcium ions from entering the muscle cells through voltage-gated calcium channels, leading to relaxation of vascular smooth muscle and reduced myocardial contractility.

Angina, or chest pain due to reduced blood flow to the heart, is effectively managed with calcium channel blockers because they reduce the heart's workload and improve blood flow to the myocardium. Hypertension, or high blood pressure, is another major indication; the vasodilatory effect of these medications helps to lower systemic vascular resistance, which decreases arterial pressure.

Pulmonary hypertension can also be treated with certain calcium channel blockers, as they can reduce vascular resistance in the pulmonary arteries, thereby improving symptoms and exercise capacity in patients with this condition.

Other options do not align with the primary pharmacological effects of calcium channel blockers. For instance, epilepsy is generally managed with anticonvulsants, while severe pain and inflammation would lean towards the use of analgesics or NSAIDs. Anxiety or respiratory distress would typically be treated with anxiolytics or bronchodilators, respectively. Thus, the focus on cardiovascular conditions in the correct option aligns with the pharmacological action of calcium channel