Adrenergic Receptor ANTAGONISTS Flashcards
Alpha Receptor Antagonists
- Nonselective example?
- Alpha 1 selective example?
- phentolamine
- prazosin
Beta Receptor Antagonists
- Non-selective (first generation) example?
- Beta 1 selective examples?
- Non-selective (third generation) example? Why are they used?
- propranolol
- esmolol and metoprolol
- Carvedilol and labetalol (used because they have additional vasodilator activities)
IGNORE Alpha adrenergic receptors mediate several functions:
- Receptor and action on smooth muscle?
- CNS receptor effect?
- Presynaptic receptor effect?
- Vagal effect? Why?
- Two other basic effects?
- Alpha 1 (some alpha 2) and contraction of arterial and venous smooth muscle
- Suppress sympathetic output
- Inhibit NE and ACh release
- Increase vagal tone as reflex effect in response to increased BP
- Facilitate platelet aggregation and regulate glucose/lipid metabolism (Alpha 2)
Alpha 1 receptor antagonists:
What does it do to catecholamines normal effect? Effect?
Inhibits catecholamine mediated vasoconstriction in arteries and veins –> reduces peripheral vascular resistance and BP. The decreased BP causes reflex increases in HR, CO, as well as fluid retention.
(inhibits vasoconstriction and increased BP in response to sympathomimetic amines)
Alpha 2 antagonists
What is an unwanted effect of alpha 2 antagonists?
Increases sympathetic outflow to the heart and blood vessels resulting in an increase in BP
What can alpha receptor antagonists do to the amount of glucose released?
Action on insulin release? Receptor?
Reduce glucose release
Facilitates insulin release; alpha 2
Haloalkylamines
- The drug associated?
- Affects what receptors? How?
- Primary results stem from blockade of receptors on ___ ___.
- Phenoxybenzamine
- Both alpha 1 and 2; irreversible
- smooth muscle
Phenoxybenzamine
- Main action?
- Impair pressor response to catecholamines resulting in?
- DECREASE TPR, INCREASE CO (reflex), and possible tachycardia (from alpha 2 block)
- hypotension, hypovolemia, and vasodilation
Phenoxybenzamine
Therapeutic uses?
Pheochromocytoma (catecholamine secreting tumor that causes severe hypertension) in preparation to remove it (bc it will release catecholamines during surgery) to control episodes of severe hypertension and injury to the myocardium
Phenoxybenzamine
Adverse effects? Why?
Due to low BP –> postural hypotension with reflex tachycardia and other arrhythmias
Due to impaired smooth muscle contraction of the vas deferens/ejaculatory ducts –> inhibition of ejaculation
Imidazolines
- Drug example?
- Receptor antagonists? Mechanism?
- CV effects?
- Phentolamine
- Both (nonselective); competitive inhibition
- similar to phenoxybenzamine: Decreases TPR, Increases CO, possible tachycardia
Phentolamine
Other than CV effects - what else can this cause?
Block 5HT receptors, release histamine (from mast cells), block K+ channels, stimulate GI smooth muscle, enhance gastric acid secretion (not good)
Phentolamine
Therapeutic uses:
- In regards to pheochromocytoma?
- In regards to clonidine?
- In regards to MAOIs?
- What are 2 additional uses?
- Decrease excessive hypertension and relieve pseudo-obstruction of the bowel
- Withdrawl of clonidine results in hypertensive crisis (this decreases hypertension)
- With tyramine ingestion hypertensive crisis occurs (results in a decrease of hypertension)
- (a) prevents dermal necrosis after the leakage of an alpha agonist (b) intracavernous injection for ED
Phentolamine
Adverse Effects/Contraindications?
- Hypotension
- Reflex cardiac stimulation with tachycardia, cardiac arrhythmias, ischemia, and MI
- GI stimulation resulting in abdominal pain/nausea (caused by increased motility by blocking SNS and increased vagal effects) and exacerbation of peptic ulcer
Alpha 1 receptor antagonists? (5)
Prazosin, Terazosin, Doxazosin, Alfuzocin, Tamsulosin
Prazosin
- Receptor antagonist?
- Pharmacological effects? Potent inhibitor of?
- Why are these better: what do they not cause?
- Alpha 1
- Antihypertensive; cyclic nucleotide PDE (vasodilator)
- Little postural hypotension, does NOT result in reflex tachycardia, no change in CO
Prazosin
Therapeutic effects?
Hypertension, CHF (doesnt prolong life!), BPH and associated lower urinary tract
Prazosin
Adverse effects and contraindications?
Primary first dose effect: marked postural hypotension and syncope within 30 to 90 minutes after an initial dose (because its very potent and causes increased vasodilation)