Peripheral Vasodilators, Capillarotonic, and Venotonic Drugs
Peripheral vasodilators are medications that relax and widen blood vessels outside the heart and brain, improving blood flow and reducing vascular resistance. Capillarotonic and venotonic drugs enhance the tone and function of capillaries and veins, improving circulation.
Classification
- Inhibitors of Renin
- Aliskiren
- ACE Inhibitors (ACEIs)
- Enalapril, Ramipril
- Angiotensin II Receptor Blockers (ARBs)
- Losartan, Valsartan
- Calcium Channel Blockers (CCBs)
- Amlodipine, Diltiazem, Verapamil
- Nitrates
- Isosorbide Mononitrate, Nitroglycerin
- Capillarotonic Drugs
- Diosmin
- Venotonic Drugs
- Hesperidin
Pharmacodynamics (Mechanism of Action)
- Renin Inhibitors (Aliskiren)
- Directly inhibits renin, preventing the conversion of angiotensinogen to angiotensin I.
- Reduces angiotensin II levels → Vasodilation, decreased aldosterone secretion, lower blood pressure.
- ACE Inhibitors (Enalapril, Ramipril)
- Inhibit angiotensin-converting enzyme (ACE), blocking the conversion of angiotensin I to angiotensin II.
- Cause vasodilation, reduced aldosterone secretion, decreased blood pressure.
- ARBs (Losartan, Valsartan)
- Block angiotensin II receptors on blood vessels & adrenal glands.
- Prevent vasoconstriction & aldosterone effects → Vasodilation, decreased blood pressure.
- Calcium Channel Blockers (Amlodipine, Diltiazem, Verapamil)
- Inhibit calcium ion influx into vascular smooth muscle & cardiac cells.
- Reduce vascular contraction → Vasodilation, lower blood pressure.
- Verapamil & Diltiazem also reduce heart rate & contractility.
- Nitrates (Isosorbide Mononitrate, Nitroglycerin)
- Release nitric oxide (NO), which activates guanylate cyclase → cGMP formation.
- cGMP causes vascular smooth muscle relaxation → Venous & arterial dilation.
- Reduces preload & afterload, improving myocardial oxygen supply.
- Capillarotonic Drugs (Diosmin)
- Strengthen capillary walls & improve microcirculation.
- Used in chronic venous insufficiency, hemorrhoids.
- Venotonic Drugs (Hesperidin)
- Improve venous tone & reduce venous stasis.
- Used for varicose veins, hemorrhoids, and venous insufficiency.