Alpha-blockers
Non-selective blockers
Uses
1) Hypertension in pheochromocytoma.
2) Symptomatic benign prostatic hyperplasia (BPH).
3) Raynaud's phenomenon.
4) Impotence.
Side Effects
1) Postural hypotension
2) Reflex tachycardia and Failure of ejaculation.
Phenoxybenzamine
It is a non-selective irreversible non-competitive.
Duration of action: 3 to 4 days. (Orally).
Tolazoline & Phentolamine
Non-selective reversible competitive.
Phentolamine more potent than Tolazoline
Duration of action
approximately 4 hours. (Parenterally)
selective alpha-1 blockers
Prazosin
Less reflex tachycardia.
Uses:
1) Treatment of hypertension
2) symptoms of BPH
3) Congestive heart failure
4) Pheochromocytoma
5) Raynaud's phenomenon.
Side Effects
1) First-dose orthostatic hypotension (initial syncope attack) to overcome he first dose must be minimized and giving at bed me.
2) Headache
3) dizziness
4) drowsiness
5) nausea
Doxazosin & Terazosin
Used Orally for: symptoms of BPH and hypertension.
Side effects: initial syncope attack.
Alfuzosin
Used for symptoms of BPH (Not for hypertension).
Alfuzosin have better CV tolerability.
Tamsulosin
Selective alpha-1a receptor blocker in the smooth muscle of prostate (not act on dis receptor in the blood vessels).
Most drug prescribed in symptoms of BPH.
Side effect Failure of ejaculation or retrograde ejaculation
selective alpha-2 blockers
Yohimbine
Uses: mydriatic and erectile dysfunction.
Beta-blockers
Non-selective blockers
Propranolol
It blocks both B1 and B2 receptors with equal affinity.
Pharmacological Action
Heart: (-ve) Inotropic & Chronotropic & slow SA and AV nodal conduction.
cardiac work and O2 consuming.
Lung: Bronchoconstriction.
Eye: B-blocking agents IOP especially in glaucoma due to aqueous humour formation.
Metabolic effects:
1) Block B-receptors in adipose tissues Which leads to decrease Lipolysis.
2) Block B2-receptors in liver Which leads to decrease Glycogenolysis.
3) Block B2- receptors in pancreas Which leads to decrease Glucagon.
N.B: Glucagon hormone used to combat hypoglycemia effects, so; non-selective ß-blockers used with caution in insulin-dependent diabetic patients.
Chronic use
increased VLDL (very low density lipoprotein) and decrease HDL (high density lipoprotein; good cholesterol) Which leads to increase risk for coronary artery disease.
Uses:
1) Hypertension.
2) Angina.
3) Myocardial Infarction.
4) Arrhythmias
5) Hyperthyroidism (inhibits the peripheral conversion of T4 to T3).
5) Migraine prophylaxis.
6) Aniaty status.
Side Effects:
1) Hypotension
2) Bronchospasm
3) Arrhythmias
4) Metabolic disturbances (fasting hypoglycemia)
5) Cold extremities
6) Male impotence
7) Sleep disturbances.
Warning: The B-blockers must be tapered off gradually.
Nadolol
Very long duration with low lipid solubility
uses
1) hypertension
2) angina
3) migraine prophylaxis.
Nadolol widely used in esophageal varices to prevent bleeding in people with portal hypertension.
Timolol
Used in chronic open-angle glaucoma.
Sotalol
It is an antiarrhythmic drug with Class II and Class III.
selective blockers
Betaxolol
Used in treatment of chronic open-angle glaucoma.
Esmolol
Ultra-short-acting (half-life: about 10 minutes) used to control blood pressure or heart rhythm during surgery.
Bisoprolol
It is used in hypertension and heart failure.
Nebivolol
Most highly selective B1-blocker with NO-potentiating effect, Used as antihypertensive & anti-anginal agent.
Metoprolol
Uses: hypertension, angina, heart failure, myocardial Infarction, arrhythmias, migraine prophylaxis & anxiety
Atenolol
Used in hypertension, angina, myocardial infarction, arrhythmias.
B-blockers with partial agonist activity
Acebutolol
It is used in hypertension & ventricular arrhythmias.
Pindolol
It is used in hypertension.
Celiprolol
B1-selective blocker and activate B2-receptors.
mixed blockers
Labetalol
Used in hypertension of pheochromocytoma and hypertensive crisis and pregnancy-hypertension associated with pre-eclampsla.
Carvedilol
Used in CHF: due to it decrease lipid peroxidation & oxidative injury to endothelial cells, decrease vascular wall thickening
4) Lippincott's Illustrated Reviews: Pharmacology
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