Lecture 14 - Alpha Blockers and Ca Channel Blockers Flashcards
Alpha affinities?
Norepinephrine > Epinephrine»_space; isoproterenol
Alpha 1?
post-synaptic, vasoconstriction, alpha1a found in prostate, alpha1b found in vascular smooth muscle
Alpha 2?
pre and post synaptic, inhibit norepinephrine and insulin release
Alpha 1 antagonism drug?
doxazosin -> vasodilation hypotension
Alpha blocker indications?
hypertension (used as combination therapy, not first line), phaeochromocytoma, prostatism
Doxazosin?
reversible alpha blocker (1»>2), blocks all subtypes, vasodilator, reduce prostatic symptoms, start low dose and titrate, once daily, liver metabolism, fecal excretion
Alpha blocker adverse effects?
hypotension, lassitude, nasal stuffiness, dry mouth, urinary incontinence
Phenoxybenzamine?
oral, irreversible alpha blocker antagonism (1 > 2), used in pheaochromocytoma and pre-operatively,
Phenoxybenzamine side effects?
decreased postural BP, tachycardia, nasal stuffiness, CNS
Alpha and beta combined therapeutics?
Labetalol (reversible, used for hypertension in pregnancy and phaeochromocytoma). Carvedilol (also anti-oxidant, used in congestive cardiac failure)
Indications for Ca channel blockers?
hypertension, angina, arrhythmias, vasospasms
Ca channel blocker physiology?
block voltage-operated L-type Ca channels of cardiac and smooth muscle, selective for resistance vessels, myocardium and conducting tissue
Ca channel blockers - vascular SM mechanism>
decreased tone, resistance and blood pressure/afterload
Ca channel blockers - cardiac mechanisms?
decreased contractility, sinus and AV node transmission
Ca channel blockers - specific drugs?
nifedipine (vessels - flushing, headaches oedema), diltiazem (both), verapamil (heart an gut - heart block, negative ionotrope, constipation)
Ca channel blockers - PK?
hepatic metabolism, short (nifedipine) or long (amlodipine) half life
Nifedipine?
used for hypertension & vasospasm, oral, liver metabolism and renal excretion, side effects oedema, flushing and headache, t1/2 few hours
Diltiazem?
used for angina, hypertension and tachyarrhythmias (AF), oral, liver metabolised and fecal excreted, side effects oedema, flushing, headache and bradycardia, can b used with beta-blockers
Verapamil?
used for tachyarrhythmias (SVT, AF) and hypertension, oral and IV, hepatic metabolism and renal excretion, 7hr t1/2, side effects bradycardia, negative inotrope and constipation
Verapamil interactions?
BETA BLOCKERS, inhibits cytc p450, care with statins, inhibits p-glycoproteins
