Adrenergic Agonists and Antagonists Flashcards
What are the indirect acting NE releasers?
Tyramine
Amphetamine
Ephedrine
Where is tyramine normally found?
Diet, aged/fermented foods like cheese and wine
Why does dietary tyramine not normally cause NE release?
Normally oxidized by MAO in gut and liver before reaching the circulation
MAO-I inhibitors will allow NE release
What are amphetamines used to treat?
Narcolepsy and ADD
What is the mechanism of action of ephedrine?
NE releaser and weak Beta2 agonist
What are the uses of ephedrine?
Decongestant
Vasopressor (BP increased)
Stress urinary incontinence (contracts bladder sphincter)
What is the difference between ephedrine and pseudoephedrine?
Less psychostimulant
Less CV effects with equivalent decongestant potency
What is the mechanism of NE release caused by the indirect acting NE releasers?
Nonvesicular release
NE-releaser displaces NE from vesicle to cytoplasm
NE released by reversal of NET
What is the mechanism by which cocaine increases NE?
Blocks neuronal NE uptake by NET
What is the direct-acting Alpha1 agonist?
Phenylephrine
What are the uses of phenylephrine?
Decongestant, vasoconstriction, mydriasis
What are the direct-acting Alpha2 agonists?
Clonidine
Brimonidine
What is clonidine used for?
Reduces sympathetic activity by inhibiting NE release (alpha2 receptors are autoreceptors)
Used for hypertension
What is Brimonidine used for?
Analog of clonidine, used to treat IOP
What are the direct-acting Beta2 agonists?
Albuterol
Salmeterol
Formoterol
Ritodrine
Which beta2 agonists are used for asthma?
Albuterol
Salmeterol
Formoterol
What is Ritodrine used for?
Delay preterm labor
What is the direct-acting Beta3 agonist?
Mirabegron
What is Mirabegron used for?
Treat overactive urinary bladder syndrome by relaxing the detrussor
What are Alpha 1 & 2 antagonists?
Phenoxybenzamine
Phentolamine
What are the Alpha 1 & 2 antagonists used for?
Management of pheochromocytoma (catecholamine-secreting tumors)
What is important to remember about the treatment of pheochromocytomas?
Alpha block must be in place before use of a beta block
If beta receptor was blocked first, would cause huge vasconstriction and increased blood pressure
What are the Alpha 1 specific antagonists and which is Alpha-1A selective?
Prazosin
Terazosin
Tamsulosin - Alpha-1A selective
What are prazosin and terazosin used for?
Primary hypertension - causes vasodilation
Vasodilation in peripheral vascular disease (Raynaud’s)
Relaxation of urinary tract smooth muscle - helpful in benign prostatic hypertrophy and voiding kidney stones
What is tamsulosin used for?
Selective relaxant of urinary tract smooth muscle with less vasodilator
What is the Alpha 2 selective antagonist?
Yohimbine
What is yohimbine used for?
Increased NE release and increased vasoconstriction
What are adverse effects of alpha 1 block?
Postural hypotension
Nasal congestion
Dry mouth
Intraoperative floppy iris syndrome (IFIS)
Retrograde ejaculation (relaxed internal sphincter allows it back up)
Delayed ejaculation (reduced propulsion of seminal fluid along vas deferens
Priapism
Why does alpha 1 block cause priapism?
Sympathetic adrenergic input and contraction of vascular and trabecular smooth muscle maintains flaccidity
Blockage of sympathetic tone relaxes blood vessels, facilitating inflow of blood and compressing veins that are draining blood, resulting in engorgement and rigidity
What are the non selective Beta blockers?
Propanolol
Timolol
Pindolol
What are cardiovascular indications for the use of Beta blockers?
Typical effort angina Postinfarction Arrhythmias Systolic heart failure Primary hypertension
What are other indications (not CV) for the use of beta blockers?
Hyperthyroidism
Migraine
Glaucoma
Tremors
What are the Beta-1 selective blockers?
Atenolol
Metoprolol
What are the nonselective beta blockers with additional vasodilator actions?
Carvedilol
Labetalol
Through what receptor does Labetalol exert its additional vasodilator effects?
Alpha 1
is an alpha1 & beta blocker
Which nonselective beta blocker is also a partial beta agonist and why is this useful?
Pindolol
Partial agonism may be advantageous in patients with bradycardia or partial conduction block
Which nonselective beta blocker has high lipid solubility?
Propranolol
Allows it to cross BBB, placenta
What are cardiovascular adverse effects of beta blockers?
Decreased exercise capacity Bradycardia AV conduction block Heart failure Peripheral vasoconstriction (cold extremities) Withdrawal beta-supersensitivity
What are non-CV adverse effects of beta blockers?
Bronchoconstriction (contraindicated in asthma/COPD)
Mast cell destabilization (dumping of inflammatory mediators, complicates treatment of anaphylaxis with epi)
Exercise induced hyperkalemia
