Which of the following anti hypertensives act by decreasing heart rate only?
Ans: a (Propranolol) Ref: Katzung, 10th ed, p. 160Beta blockers decrease heart rate, force of contraction and cardiac output, this leads to decrease in blood pressure.Drugs used in hypertension are:1) Diuretics - Low-dose thiazide diuretics are often used as first-line agents, alone or in combination with other antihypertensive drugs e.g., hydrochlorthiazide, chlorthalidone.2) ACE-inhibitors and angiotensin receptor blockers - ACE inhibitors decrease the production of angiotensin n, increase bradykinin levels, and reduce sympathetic nervous system activity. Angiotensin II receptor blockers provide selective blockade of AT1 receptors.3) Beta Blockers - a adrenergic receptor blockers lower blood pressure by decreasing cardiac output, due to a reduction of heart rate and contractility. Other actions include renin inhibition.4) Calcium Channel Blockers - Calcium channel antagonists reduce vascular resistance through L- channel blockade, which reduces intracellular calcium and blunts vasoconstriction.5) Aldosterone Antagonists - It may be a particularly effective agent in patients with low-renin essential hypertension, resistant hypertension, and primary aldosteronism.The newer agent, eplerenone, which is a selective aldosterone antagonist have lesser side effects than spironolactone.6) a adrenergic blockers - They lower blood pressure by decreasing peripheral vascular resistance.7) Sympatholytic Agents - Centrally acting a2 agonists lower blood pressure by inhibiting sympathetic outflow and thereby decreasing peripheral resistance e.g., clonidine.8) Direct vasodilators - These agents decrease peripheral resistance.Hydralazine is a potent direct vasodilator.S/e: lupus-like syndrome.Minoxidil is another vasodilator and is most frequently used in patients with renal insufficiency that is refractory to all other drugs.S/e: hypertrichosis and pericardial effusion.9) Adrenergic neuron-blocking agents-These drugs lower blood pressure by preventing normal physiological release of norepinephrine from postganglionic sympathetic neurons.E.g. Guanethidine, reserpine
Propranolol
Methyl dopa
Prazosin
Nitrate
C.V.S