Antiadrenergic Drugs PDF

Antiadrenergic Drugs Prof. Murat Oz Faculty of Pharmacy Kuwait University Phenoxybenzamine is a noncompetitive blocker of α1 and α2 receptors. It is used in the treatments of sweating and hypertension of pheochromocytoma, Raynaud disease and frostbite Phentolamine is a compet...

Antiadrenergic Drugs Prof. Murat Oz Faculty of Pharmacy Kuwait University Phenoxybenzamine is a noncompetitive blocker of α1 and α2 receptors. It is used in the treatments of sweating and hypertension of pheochromocytoma, Raynaud disease and frostbite Phentolamine is a competitive blocker of a1 and α2 receptors. It is used for treatment of hypertension. Prazosin, Terazosin, and Doxazosin are selective and competitive blockers of the a1 receptor. They decrease peripheral vascular resistance, lower blood pressure by causing relaxation of both arterial and venous smooth muscle and used in the treatment of hypertension. They are also used in benign prostatic hyperplasia. Tamsulosin, Alfuzosin, and Silodosin are other selective a1 antagonists and used in the treatment of benign prostatic hyperplasia. Yohimbine is a competitive a2 blocker. It has been used as a sexual stimulant and in the treatment of erectile dysfunction. Adverse effects of a-adrenergic blockers include lack of energy, nasal congestion and those shown on the right panel Clinical uses of α-adrenergic receptor antagonists: -In treatment of Pheochromocytoma. Administration of phenoxybenzamine in the preoperative period helps to control hypertension -In the management of hypertensive emergencies -In treatment of Benign prostatic hyperplasia (Prazosin, Terazosin, Doxazosin, Tamsulosin, Alfuzosin, and Silodosin) -In treatment of Raynaud disease and frostbite Propranolol blocks both β1 and β2 receptors. Esmolol has the shortest (10 min). Nadolol and Nebivolol have longest (10-30 hours) half-lives. Main effects are shown on the left. In addition, β-blockade leads to decreased glycogenolysis and decreased glucagon secretion and attenuate the normal physiologic response to hypoglycemia. Thus, pronounced hypoglycemia occurs after insulin injection in β-blocker users. β-Blockers are used in treatment of 1) systemic as well as portal hypertension, 2) angina, 3) cardiac arrhythmias, 4) myocardial infarction, 5) heart failure, 6) hyperthyroidism, 6) glaucoma and 7) prophylaxis of migraine, 8) performance anxiety. Nadolol and Timolol also block β1 and β2 adrenoceptors. Timolol reduces the production of aqueous humor in the eye and used topically in the treatment of chronic open-angle glaucoma. Pilocarpine (muscarinic agonist) is used in acute glaucoma Acebutolol, Atenolol, Betaxolol, Bisoprolol, Esmolol, Metoprolol, and Nebivolol are selective β-1 antagonists. The cardioselective β-blockers are used in hypertensive patients with impaired pulmonary function. These agents are also first-line therapy for chronic stable angina. However, in general, β-blockers should be avoided in Asthmatic patients. Acebutolol and Pindolol have partial agonist activity on β1 and β2 receptors (intrinsic sympathomimetic activity). They are used in treatment hypertension with bradycardia. Labetalol and Carvedilol are non-selective antagonists of both α and β adrenoceptors. Labetalol is used for pregnancy-induced hypertension and carvedilol is used in treatment of stable chronic heart failure. Side effects of β blockers: 1) Bradycardia, 2) Sedation and depression (nadolol, atenolol), 3) Hypoglycemia in diabetic patients, Other side effects of β-blockers are shown on the right. In addition, nonselective β-blockers increases triglycerides and reduces high-density lipoprotein ("good" cholesterol). These effects are less pronounced with β1- antagonists such as metoprolol. Reserpine, a plant alkaloid, blocks the transport of biogenic amines (norepinephrine, dopamine, and serotonin) from the cytoplasm into storage vesicles in the adrenergic nerve terminals and causes depletion of biogenic amines. It was used for the management of hypertension, and also indicated in agitated psychotic states such as schizophrenia THANKS