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Index
»
PHARMACOLOGY 1
»
CHAPTER 7 Adrenergic Antagonists
»
Level 1
level: Level 1
Questions and Answers List
level questions: Level 1
Question
Answer
• also called ADRENERGIC BLOCKERS or SYMPATHOLYTICS • drugs that BLOCK the action of norepinephrine and epinephrine in adrenergic receptors
Adrenergic Antagonists
• binds covalently to alpha receptors (both 1 and 2), causing irreversible blockade of long duration (14-48 hours or longer) • CA: major use is in the treatment of PHAECHROMOCYTOMA; RAYNAUD DISEASE • S/E: orthostatic hypotension and tachycardia; nasal stuffiness and INHIBITS MALE EJACULATION
Phenoxybenzamine
• a TUMOR of the adrenal medulla or sympathetic ganglion cells • the tumor secretes norepinephrine and epinephrine
Phaeochromocytoma
• a potent competitive antagonist at both alpha 1 and alpha 2 receptors (short-acting) • used in the treatment of Phaeochromocytoma; treatment of HYPERTENSIVE CRISIS due to abrupt withdrawal of Clonidine • S/E: severe tachycardia, arrythmia and myocardial ischemia
Phentolamine
• effective in the management of HYPERTENSION • SELECTIVE ALPHA-1 receptor ANTAGONIST • RELAXES both arterial and venous vascular smooth muscle, as well as smooth muscle in the prostate
Prazosin
• reversible alpha-1 selective antagonist that is effective in HYPERTENSION • also approved in men with urinary symptoms due to BENIGN PROSTATIC HYPERPLASIA
Terazosin
• efficacious in the treatment of hypertension and BPH • has LONGER haf-life compared to prazosin and terazosin
Doxazosin
• a competitive alpha-1 receptor antagonist with a structure quite different from that of most other alpha-1 antagonists • GREATER POTENCY in INHIBITING CONTRACTION in PROSTATE smooth muscle
Tamsulosin
• is an α1-selective QUINAZOLINE derivative that is approved for use in BPH
Alfuzosin
• used as an antihypertensive • not available in the USA
INDORAMIN
• an α1-antagonist that also has α2- agonist actions and weak antagonist action at β1-receptors • used in Europe as an antihypertensive agent and for benign prostatic hyperplasia
URAPIDIL
• has both α1-selective and βantagonistic effec
LABETALOL
• Examples: Chlorpromazine and Haloperidol • are potent dopamine receptor antagonists but are also antagonists at α-receptors • antagonism of α receptors probably contributes to some of their adverse effects, particularly hypotension
NEUROLEPTIC DRUGS
• an antidepressant that has the capacity to block α1-receptors
TRAZODONE
• Examples: Ergotamine and Dihydroergotamine • cause reversible α-receptor blockade, probably via a partial agonist action
ERGOT DERIVATIVES
• an indole alkaloid • an α2-SELECTIVE ANTAGONIST • sometimes used in the treatment of orthostatic hypotension because it promotes norepinephrine release through blockade of presynaptic α2 receptors • once used to improve male erectile dysfunction but has been superseded by phosphodiesterase-5 inhibitors like sildenafil • can reverse the antihypertensive effects of an α2-adrenoceptor agonist such as clonidine
YOHIMBINE