yang Flashcards
what drugs are alpha-1 antagonists?
prazosin
terazosin
doxazosin
what is the pk of alpha-1 antagonists?
prazosin –> 3 hours
terazosin –> 12 hours
doxazosin –> 20 hours
what is the metabolism of alpha-1 antagonists?
extensive metabolism that is excreted in the bile
what is the MOA of prazosin?
Alpha-1 antagonism decreases TPR –> activates the baroreceptor reflex —-> increases NE release into the myocardium –> increase in HR via beta-1 receptors.
Negative feedback via alpha-2 receptors in the myocardium mitigates NE release
what are alpha-1 antagonists?
quinazolines that produce vasodilation via alpha-1 antagonism in arterioles and venules without causing reflex tachycardia or increased CO (presynaptic alpha-2 effect)
what are the effects of alpha-1 antagonists?
decrease TPR with less reflex tachycardia than nonselective antagonists (phentolamine)
what are the compensatory effects of alpha-1 antagonists?
reflex tachycardia
renin release
co-administer diuretic to decrease retention of salt and water
what are the clinical use of alpha-1 antagonists?
BPH
HTN (not first line)
reynaud’s disease
what is reynaud’s disease
numbness due to cold or stress producing vasconstriction in hands/feet
what are the problems with alpha-1 antagonists?
first dose phenomenon (most common with prazosin)
what is the first dose phenomenon?
orthostatic hypotension and syncope particularly with first dose
what are the effects of direct-acting alpha-2 agonists?
inhibit NE release and decrease sympathetic tone in CNS –> resulting in decreased HR, contractility, and renin release, and less vasoconstriction
what is clonidine?
alpha-2 agonist and imidazoline receptor
activates the presynaptic alpha-2 receptor in the CNS to decrease SNS activity to the heart and blood vessels
how is clonidine administered?
oral
parenteral
transdermal
what is the half life of clonidine?
8-12 hours
is clonidine lipophilic or hydrophilic?
lipophilic
what are the clinical uses of clonidine?
HTN
ADHD
neuropathic pain/opiate withdrawal
restless leg syndrome
what are the SE of clonidine?
hypotension
sedation
dry mouth
withdrawal syndrome after prolonged use –> HTN tachycardia, angina, MI so taper dose
what are guanabenz and guanfacine?
oral direct acting alpha-2 agonists and open ring imidazolidines that are mostly non-ionized at physiological pH
what is the half life of guanabenz?
6 hours
what is the half life of guanfacine?
12-16 hours
what is the clinical usage of guanabenz and guanfacine?
HTN
ADHD
what is methyldopa?
oral direct-acting alpha-2 agonist and prodrug that reduces sympathetic outflow
what is the metabolic pathway of methyldopate
methyldopate –> methylopa (via esterase) –> alpha-methyldopamine (via L-aromatic amino acid decarboxylase) –> (IR,2S)-alpha-methylnorepineprhine (via dopamine beta-hydroxylase)
what is methyldopate?
ester hydrochloride salt that is water soluble and used parenterally
what is the clinical use of methyldopa?
HTN especially in pregnancy
what drugs are central acting alpha-2 agonists?
clonidine
methyldopa
guanabenz
guanfacine
what is the action of methyldopa?
false transmitter that displaced NE from vesicle
what are the effects of alpha-2 agonists?
decrease TPR, HR, and renin activity
what are the SE of methylopa?
sedation
sodium/water retention (combine with diuretic)
what is the impact of beta blockers on angina?
reduce myocardial oxygen demand via reduced HR and contractility