Pathophysiologyand Pharmacology of Hypertension
Hypertensionis characterized by abnormal high blood pressure in the body. Normalblood pressure is a product of systemic vascular resistance andcardiac output. This means that individuals suffering from high bloodpressure have increased cardiac output and elevated vascularresistance. One of the factors that can cause this elevation isincreases in alpha-adrenoreceptor stimulation. High blood pressureis also attributed to an increase in peptides such as angiotensin orendothelins (Porth, 2011). These substances exert theirpharmacological effects by increasing the vascular tone andresistance and high muscular stiffness thus resulting inhypertension. In some cases, high blood pressure have been linked tothe autonomic nervous system. For example, in hypotensive patients,there is increased release and high peripheral sensitivity tonorepinephrine.
Drugsused in managing hypertension are called antihypertensive and areclassified into five categories namely, diuretics, sympatholytic,vasodilators, calcium channel blockers and angiotensin-convertingenzyme inhibitors. The diuretics include thiazides, potassiumsparring, and loop diuretics. Thiazides, like chlorothiazide act bydecreasing sodium reabsorption in the distal tubule. This leads toloss of potassium through the exchange mechanism. Hypotensiveactivity of thiazides is causes reduction in vascular resistance dueto a decrease in blood volume. Loop diuretics like furosemide act atthe ascending limb of the loop of Henle. They also work by reducingthe reabsorption of sodium and chloride. This results in anincreased renal blood flow due to reduced renal vascular resistance.Sympatholytic act by inhibiting the movement of adrenaline from thebrain, therefore reducing blood pressure. Examples are methyldopa andreserpine. Vasodilators like nitroprusside sodium act by activationof ATP-sensitive potassium channels. This results in hyperpolarization of the arteriolar smooth muscle, hence relaxation.Calcium channel blockers like nifedipine act by reducing vascularmuscle tone due to their ability to reduce the transmembrane movementof calcium ions. Angiotensin converting enzyme inhibitors likeenalapril act by reducing the amount of angiotensin 2 produced.
Porth,C. (2011). Essentialsof pathophysiology: Concepts of altered health states.Lippincott Williams & Wilkins.