Study Set Content:
Theses are drugs that binds to adrenergic receptors but do not initiate the usual intracellular response.
ADRENERGIC ANTAGONISTS
Major divisions
-blockers
• -blockers
This chapter deals with pharmacologic antagonist drugs whose major effect is to occupy a 1, a 2, or ß receptors outside the central nervous system and prevent their activation by
catecholamines and related agonists.
nonselective a antagonists used in the treatment of ____ (tumors that secrete catecholamines),
pheochromocytoma
are used in primary hypertension and benign prostatic hyperplasia.
+ 1 -selective antagonists
are useful in the treatment of hypertension, ischemic heart disease, arrhythmias, endocrinologic and neurologic disorders, glaucoma, and other conditions.
Beta-receptor antagonist drugs
Examples of a-blockers:
Prazosin (Minipress)
Doxazosin (Cardura
Terazosin (Hytrin)
Phenoxybenzamine (Dibenzyline
Yohimbine (Yocon)
Phentolamine (Regitine
1-adrenergic selective, reversible
Prazosin (Minipress) -
₁-adrenergic selective, reversible
Doxazosin (Cardura)
₁-adrenergic selective, reversible
Terazosin (Hytrin
nonselective, irreversible (remember: phenoxybenzamine is the only a-adrenergic receptor mentioned that is nonreversible)
Phenoxybenzamine (Dibenzyline
₁-adrenergic selective, reversible
Yohimbine (Yocon)
nonselective, reversible
Phentolamine (Regitine)
Mechanism of Action:
•_____ may be reversible or irreversible in their interaction with these receptors.
Alpha-receptor antagonists
dissociate from receptors, and the block can be Surrounded with sufficiently high concentrations of agonists.
Reversible antagonists
-used as antihypertensive drug largely dependent on the half-life of the drug in the body and the rate at which it dissociates from its receptor.
Labetalol
(A) Cardiovascular Effects
• A-receptor antagonist drugs cause a () of peripheral vascular resistance and blood pressure
lowering
In the case of agonists with both a and ß 2 effects (eg, epinephrine), selective a-receptor antagonism may convert a pressor to a
depressor response
This change in response is called epinephrine reversal; + a-receptor antagonists often cause
orthostatic hypotension and reflex
may be more marked with agents that block a 2 -presynaptic receptors in the heart, since the augmented release of norepinephrine will further stimulate ß receptors in the heart.
Tachycardia
