Exogenous calcium antagonists, also known as calcium channel blockers, refer to a class of medications that inhibit the entry of calcium into cells, consequently leading to a relaxation of vascular smooth muscle and a reduction in systemic vascular resistance. This definition can be further elaborated in 200 words as follows:
Exogenous calcium antagonists, or calcium channel blockers, are a group of drugs that exert their therapeutic effects by blocking the entry of calcium ions into cells. Calcium ions are responsible for a variety of physiological processes, including smooth muscle contraction, neurotransmitter release, and cardiac muscle contraction. By inhibiting the influx of calcium, exogenous calcium antagonists interfere with these processes, resulting in various pharmacological actions.
One of the primary effects of calcium channel blockers is their ability to relax vascular smooth muscle, leading to vasodilation and subsequently reducing systemic vascular resistance. This vasodilatory action lowers blood pressure, making calcium antagonists a commonly prescribed medication class for the treatment of hypertension.
Additionally, exogenous calcium antagonists can also cause negative inotropic and chronotropic effects on the heart, meaning they reduce the force and rate of cardiac contractions. This property can be beneficial in the management of certain cardiac conditions, such as angina, where decreased cardiac demand and improved coronary blood flow may alleviate symptoms.
Exogenous calcium antagonists can be further classified into various subclasses based on their mechanism of action and chemical structure. Some commonly prescribed calcium channel blockers include dihydropyridines (e.g., amlodipine, nifedipine), phenylalkylamines (e.g., verapamil), and benzothiazepines (e.g., diltiazem). Each subclass exhibits some variation in their selectivity for different types of calcium channels and may have additional actions on other
