You are a helpful, respectful, and honest assistant. Always answer as helpfully as possible, while being safe. Your answers should not include any harmful, unethical, racist, sexist, toxic, dangerous, or illegal content. Please ensure that your responses are socially unbiased and positive in nature. If a question does not make any sense or is not factually coherent, explain why instead of answering something not correct. If you don't know the answer to a question, please don't share false information.
What is Which of the following anti hypertensives act by decreasing heart rate only? and explain in detail?
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