Adrenergic Receptor Antagonists
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Transcript of Adrenergic Receptor Antagonists
Adrenergic Receptor Antagonists• Excessive sympathetic activity is characteristic of
a number of pathological states including:• Hypertension• Angina pectoris • Cardiac arrhythmias
• Sympatholytics – adrenergic receptor antagonists• Block , or both • Therapeutic effects due to 1 and 1 blockade• Adverse effects due to 2 and 2 blockade• Therefore 1 and 1 selective antagonists
59-291, Section 2, Lecture 5
Non-selective -blockers• Block both 1 and 2 receptors
– Ie. phentolamine and phenoxybenzamine Competitive
inhibitor Non-competitive
inhibitor
Chemical sympathectomy
Hypertensive Episodes
- decreases vascular resistance - lowers BP - smooth muscle relaxation in the bladder
Used to treat hypertensive episodes of Pheochromocytoma
Selective 1-blockers• Selectively block 1 receptors
– Ie. Alfuzosin, doxazosin, prazosin, terazosin•Used in the treatment of chronic hypertension• Also used to treat urinary retention in men with benign prostatic hyperplasia
Selective 1 blockers cause less reflex tachycardia than phenoxybenzamine and phentolamine
Adverse effect of 1 blockers
• Mostly caused by excessive vasodilation• Hypotension, dizziness, fainting, reflex
tachycardia, palpitation• First-dose syncope: effect on BP when
they are initially administered
-adrenergic receptor antagonists
• Both non-selective and selective -blockers• Non-selective
– ie nadolol, pindolol, propranolol, tomilol– Block both 1 receptors in cardiac tissue and 2 in smooth muscle, liver and other tissues
• Blockade of 1 reduces sympathetic stimulation of heart…
Therefore, negative
• Blockade of 2 may cause broncoconstriction and limit glycogenolysis Adverse effects!!
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1-antagonist _____
1-antagonists --------
Selective 1-blockers
• Have greater affinity for 1 than for 2 receptors– Ie Acebutolol, atenolol, esmolol, metoprolol
CARDIOSELECTIVE BLOCKERS• Produce fewer adverse effects than non-
selective, but their selectivity is not absoluteIn summary,
-blockers have a number of clinical applications including treatment of:• migraines• Hypertension• angina pectoris• cardiac arrhythmia• glaucoma
1- Contract vascular smooth muscle, iris, bladder sphincter muscle
2-Inhibits NE release
2- Relaxes bronchial, uterine, and vascular smooth muscle
2-mediates platelet aggregation;decrease insulin secretion; decreases secretion of aqueous humor 2-inhibits platelet aggregation; promotes glycogenolysis
Practice Questions• Blockade of which receptors is responsible
for the therapeutic and adverse effects of adrenergic receptor agonists?
• Therapeutic: 1, 1• Adverse: 2, 2
• Which type of drugs causes chemical sympathectomy? Give an example?
• Non-Competitive blocker• phenoxybenzamine
• What type of adrenergic receptor antagonists can be used in treatment of nocturia in benign prostate hyperplasia? Give an example.
1 blockers• Alfuzosin, doxazosin, prazosin, terazosin