Mechanism of action of antihypertensive drugs
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Major Classes of Antihypertensive Drugs and Their Mechanisms of Action
Antihypertensive drugs work through several main mechanisms to lower blood pressure, and these mechanisms are the basis for classifying the drugs into different groups. The five major classes are beta-blockers, diuretics, angiotensin-converting enzyme (ACE) inhibitors, angiotensin II receptor blockers (ARBs), and calcium channel blockers. Additional classes include renin inhibitors, alpha-adrenergic blockers, centrally acting agents, and direct vasodilators 234.
Beta-Blockers: Blocking Sympathetic Effects
Beta-blockers reduce blood pressure by blocking beta-adrenergic receptors, which decreases heart rate and the force of heart contractions. This leads to reduced cardiac output and lower blood pressure 234.
Diuretics: Promoting Sodium and Water Excretion
Diuretics lower blood pressure by increasing the excretion of sodium and water from the kidneys. This reduces blood volume and, consequently, blood pressure 2347.
ACE Inhibitors and ARBs: Inhibiting the Renin-Angiotensin System
ACE inhibitors block the conversion of angiotensin I to angiotensin II, a substance that narrows blood vessels. ARBs block the action of angiotensin II at its receptor. Both mechanisms result in blood vessel relaxation and lower blood pressure 2347.
Calcium Channel Blockers: Reducing Vascular Resistance
Calcium channel blockers prevent calcium from entering the muscle cells of the heart and blood vessels. This causes the blood vessels to relax and dilate, reducing resistance and lowering blood pressure 2347.
Additional Mechanisms: Renin Inhibitors, Alpha-Blockers, and Vasodilators
Renin inhibitors block the activity of renin, an enzyme involved in blood pressure regulation. Alpha-adrenergic blockers relax certain muscles and help small blood vessels remain open. Direct vasodilators act directly on the blood vessel walls to relax and widen them, lowering blood pressure 234.
Central and Peripheral Actions of Antihypertensive Drugs
Some antihypertensive drugs act centrally, meaning they affect the brain’s regulation of blood pressure. These drugs, such as clonidine and methyldopa, reduce sympathetic nervous system activity by stimulating central alpha-2 adrenergic receptors, leading to decreased heart rate and dilation of blood vessels 468. There is also evidence that some drugs may act on imidazoline receptors in the brain, but the main effect is still thought to be through alpha-2 receptors .
Renal Mechanisms and Long-Term Blood Pressure Control
Many antihypertensive drugs also act on the kidneys, either by dilating the renal blood vessels or by inhibiting the reabsorption of sodium and water in the kidney tubules. This helps the kidneys regulate blood volume and pressure over the long term .
New and Dual-Action Antihypertensive Drugs
Recent research has focused on developing drugs with new or dual mechanisms of action. For example, some new drugs stimulate soluble guanylate cyclase (sGC), leading to increased production of cGMP, a molecule that relaxes blood vessels independently of nitric oxide 910. Other compounds have been designed to inhibit both ACE and neutral endopeptidase, providing a dual effect on blood pressure regulation .
Conclusion
Antihypertensive drugs lower blood pressure through a variety of mechanisms, including reducing heart rate, promoting fluid excretion, relaxing blood vessels, and inhibiting hormonal systems that raise blood pressure. These mechanisms can act at different sites in the body, such as the heart, blood vessels, brain, and kidneys. Ongoing research continues to develop new drugs with improved efficacy and safety by targeting multiple pathways involved in blood pressure regulation 23457910.
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