Alpha blockers and adrenergic blockers Flashcards
types of Alpha receptor antagonists
Nonselective, a1-selective, a2-selective
Nonselective Alpha blockers
- phenoxybenzamine
- Phentolamine
Selective alpha 1 blockers
More systemic affects:
- Prazosin
- terazosin
- Doxazosin
local side effects of non-selective alpha antagonists
Nasal congestion and difficulty in ejaculation
systemic side effects of non-selective alpha antagonists
- reflex tachycardia
- systemic extracellular fluid retention
- orthostatic hypotensive symptoms
pharmacokinetics of phenoxybenzamine
Long acting irreversible inhibitor of Alpha receptors
Phenoxybenzamine clinical use
Main benefit is to treat pheochromocytoma
- treats sweating and hypertension associated with pheochromocytoma
benefit of phenoxybenzamine versus other alpha antagonists
blocks both alpha receptors and is a non competitive inhibitor
pharmacokinetics of phentolamine
nonselective(reversibly inhibits both alpha receptors)
- short acting
clinical use of phentolamine
blocks epi release during adrenal gland removal
- reverses necrosis when missing vein with NE
Historically diagnosis of phenochromocytoma
phentolamine adverse effects
gastrointestinal
prazosin clinical use
treat mild to moderate hypertension
- also treats Raynaud phenomenon (excessive vasoconstriction) if CCB doesn’t work
- off label PTSD and sleep disruption treatment
why is prazosin not used as a mono therapy
the ALLHAT study found that mono therapy did not protect against cardiovascular end points
what is prazosin attractive for
male patient with both hypertension and BPH because it treats both at the same time
what is the initial therapy for Raynaud phenomenon
calcium channel blockers
prazosin adverse effects
- orthostatic hypotension while standing.
(dose titration helps) - Edema occurs as well
- tachycardia
differences of doxazosin and terazosin with Prazosin
Prazosin has a much smaller half life
doxazosin and terazosin clinical use
- Similar to Prazosin +
- treats BPH
- induces apoptosis in prosthetic smooth muscle cells
symptoms of Benign prosthetic hyperplasia (BPH)
with BPH the prostate becomes larger which cause obstructive urinary symptoms. Which in turn a person cannot void their bladder. so must go to the bathroom often
Benign prosthetic hyperplasia (BPH) long acting alpha-1 antagonists
Doxazosin, terazosin, Alfuzosin,
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tamsulosin adverse side effects
abnormal ejaculation
alfluzosin
Demonstrates functional uroselectivity
a1 blocker for BPH
centrally acting sympathetic neuronal blockers
- methyldopa
- clonidine
- Guanfacine (Intuniv)
centrally acting adrenergic neuronal inhibitors function
a2- receptor agonists
prominent effects at CNS a2 sites.
centrally acting adrenergic neuronal inhibitors act on vasomotor centers
Decreases sympathetic outflow to peripheral organs such as heart and kidney
- no reflex mediated only CNS effects
Methyldopa mechanism of action
prodrug that convert dopa to dopamine to NE to methylnorepinephrine
- decreases renin release, decreased heart rate, and decreased peripheral resistance
- decreases sympathetic nervous system
Methyldopa clinical use
treats hypertension in pregnancy
- longest clinical data
Methyldopa adverse effects
- sedation
- edema
- dry mouth
- autoimmune disorder causes positive Coombs test
- hemolytic anemia
-abnormal liver tests
Clonidine mechanism of action
Decreases sympathetic outflow from CNS
Clonidine clinical use
- primary hypertension
- not for initial treatment
-oral or transdermal for BP control - ADHD
- Epidural
- withdrawal
- menopause
- lower intraocular pressure
Clonidine adverse effects
- Sedation
- 50% of patients get dry mouth
- sexual dysfunction
- rebound hypertension with abrupt stop
Guanfacine clinical use
- primary hypertension (not desirable)
- Primarily ADHD if stimulants don’t work
