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- 2. • adrenergic antagonistsalso called adrenergic blockers • sympatholytics
- 4. α-ADRENERGIC BLOCKING AGENTS •Drugs that block α adrenoceptors profoundly affect blood pressure. • Recetpotors ?? Nonselective A. Phenoxybenzamine • Nonselective • Linking covalently to both α1 and α2 receptors • The block is irreversible and noncompetitive, • the actions of phenoxybenzamine last about 24 hours.
- 5. • Therapeutic uses:Phenoxybenzamine is used in the treatment of • pheochromocytoma, a catecholamine-secreting tumor of cells derived from the adrenal medulla. • It may be used prior to surgical removal of the tumor to prevent a hypertensive crisis, • it is also useful in the chronic management of inoperable tumors. • Phenoxybenzamine is sometimes effective in treating Raynaud disease and frostbite. • 3. Adverse effects: • can cause postural hypotension, • nasal stuffiness, • nausea, vomiting. • It may also induce reflex tachycardia, which is mediated by the baroreceptor reflex. .
- 6. Phentolamine produces a competitiveblock of α1 and α2 receptors lasts for approximately 4 hours after a single injection., • it produces postural hypotension. • Phentolamine-induced reflex cardiac stimulation and tachycardia are mediated by the baroreceptor reflex and by blocking the α2 receptors of the cardiac sympathetic nerves. The drug can also trigger arrhythmias and anginal pain, and phentolamine is contraindicated in patients with coronary artery disease. Phentolamine is used for the short-term management of pheochromocytoma.. • Phentolamine is useful to treat hypertensive crisis due to abrupt withdrawal of clonidine and from ingesting tyramine-containing foods in patients taking monoamine oxidase inhibitors.
- 7. C. Prazosin, terazosin,doxazosin, tamsulosin, and alfuzosin • Prazosin, terazosin and doxazosin are selective competitive blockers of the α1 receptor • useful in the treatment of hypertension. • Tamsulosin and alfuzosin are examples of other selective α1 antagonists indicated for the treatment of benign prostatic hyperplasia • (BPH). • Pharmakokinetics:Metabolism leads to inactive products that are excreted in urine except for those of doxazosin, which appear in feces. • Doxazosin is the longest acting of these drugs
- 8. • Mechanism ofaction:decrease peripheral vascular resistance and lower blood pressure by causing relaxation of both arterial and venous smooth muscle.
- 9. • Therapeutic uses:Individuals with elevated blood pressure treated. • However, the first dose of these drugs may produce an exaggerated orthostatic hypotensive response that can result in syncope (fainting). • This action, termed a “first-dose” effect, may be minimized by adjusting the first dose to one-third or one-fourth of the normal dose and by giving the drug at bedtime. • These drugs may cause modest improvement in lipid profiles and glucose metabolism in hypertensive patients. • The α1 receptor antagonists have been used as an alternative to surgery in patients with symptomatic BPH
- 10. Adverse effects: Headache anddiziness Sexual dysfunction Tachycardia Orthostatic hypotension
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- 13. Nonselective β-Blockers [Firstgeneration β-blockers) • propanolol, timool, nadolol, pindolol, alprenolol and Oxprenolol. • Important effects of these drugs are: • Myocardial oxygen demand is decreased due to blockade of β1 receptors in the heart(useful in classical angina) but coronary vasoconstriction can occur due to blockade of vasodilatory β2 receptors (contraindicated in variant angina). • Decrease in blood pressure (mainly due to β1 blockade). • Bronchoconstriction may occur due to blockade of β2 receptors (contraindicated in asthmatics). • Dyslipidemia characterized by increase in LDL and decrease in HDL may be seen (β2 blockade). • Decreased chances of reversal of hypoglycemia in patients on insulin and other hypoglycemic agents (β2 blockade). • Decreased production of aqueous humor (useful in glaucoma) by β2 blocking action. • Impaired exercise capacity due to blockade of β2 receptors in blood vessels of skeletal muscle. • Abolishes sympathetic tremors (β2 blockade).
- 15. Nadolol and timolol:Nonselective β antagonists • block β1- and β2-adrenoceptors and are more potent than propranolol. • Nadolol has a very long duration of action Timolol reduces the production of aqueous humor in the eye. • It is used topically in the treatment of chronic open-angle glaucoma
- 16. Acebutolol, atenolol, betaxolol,bisoprolol, esmolol, metoprolol, and nebivolol: Selective β1 antagonists • Actions: These drugs lower blood pressure in hypertension and increase exercise tolerance in angina
- 17. DRUGS AFFECTING NEUROTRANSMITTER RELEASEOR UPTAKE • Reserpine, a plant alkaloid, blocks the Mg2+/adenosine triphosphate– dependent transport of biogenic amines (norepinephrine, dopamine, and serotonin) from the cytoplasm into storage vesicles in the adrenergic nerve terminals in all body tissues. • This causes the ultimate depletion of biogenic amines. Sympathetic function, in general, is impaired because of decreased release of norepinephrine. • Reserpine has a slow onset, a long duration of action, and effects that persist for many days • It has been used for the management of hypertension • but has largely been replaced with newer agents with better side effect.