Adrenoceptor Blocking Agents. Subat Turdi . Adrenergic Blocking Agents. Alpha Adrenoceptor Blocking Agents. Beta Adrenoceptor Blocking Agents. Non-Selective Propranolol ( Prototype) Nadolol Timolol *Pindolol *Carteolol. Non-Selective Phenoxybenzamine Phentolamine.
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Very Short Acting
Alpha and Beta Blocker
Both bind both 1 & receptors
1. Vascular. Dependent on the degree of sympathetic tone. i.e., blocks the effects of endogenous NE. See reduced blood pressure. Orthostatic hypotension.
2. Cardiac. Reflex tachycardia from reducing BP, which enhances NE release. Because alpha-2 receptors on adrenergic nerves are also blocked, this further increases NE release at the heart, where it can act on beta-1 receptors.
3. CNS. lipophilic agent which can cross the blood brain barrier. Nausea, vomiting and weakness may be signs of non-specific effects.
4. Others: miosis, inhibition of ejaculation, stuffy nose (all alpha1 blockade).
1. Pheochromocytoma: Pre-operative management to treat vascular effects of high circulating catecholamines.
2. Peripheral Vascular Disease. Raynaud’s syndrome where sympathetic tone to peripheral vasculature is high. Acrocyanosis from frost bite.
1. Pheochromocytoma. Acute hypertensive crisis.
2. Clonidine withdrawal
3. Treat necrosis due to vasoconstrictors such as NE and phenylephrine.
4. For erectile dysfunction (ED) – has been replaced by drugs with less severe side-effects.
A. Propranolol (Inderal) is the prototype
High therapeutic doses may also have a non-receptor related quinidine-like or membrane-stabilizing effects.
Relatively high lipid solubility allows distribution to the CNS (some drowsiness)
1. Heart. decreases HR, CO, and pacemaker activity.
2. Blood vessels. Slow developing decrease in peripheral resistance. Possibly due to: central reduction in sympathetic tone and reduction in renin release (beta-1 effect)
3. Bronchial Smooth Muscle.
4. Metabolic. Blocks beta receptor effects on lipolysis and glycogenolysis.
5. Quinidine-like effect.
1. Angina pectoris. Reduces cardiac work and O2 consumption.
2. Hypertension. Decreases CO and produces slow decrease in peripheral resistance due to blockade of renin release. May see Na+ and water retention with prolonged use because of reduced CO.
3. Migraine headache (Prophylactic treatment)
4. Arrhythmias: sinus tachycardia and supraventricular ectopic beat
They must be used very cautiously if at all in patients with reactive (asthma) airways.
No demonstrated therapeutic advantage over pure antagonists. Lessened bradycardia, better lipid profile ?
ISA (Intrinsic sympathomimetic activity)