beta-blocker Flashcards
uses of beta blockers
- hypertension
- angina
- heart failure
- arrhythmias (AF, atrial flutter, SVT)
mechanism of action
- block post-synaptic β receptors → inhibiting sympathetic activity
- chronic β-blockage changes kinase activity associated w/ β-receptors
- post-synaptic membrane up-regulates β receptors
receptor type and effect in the heart
B1
tachycardia, increased contractility, relaxation
receptor type and effect in the kidneys
B1 and B2
causes renin release
difference between water soluble and lipid soluble drugs
water soluble
- elimination by the kidneys
- e.g. atenolol, sotalol
lipid soluble
- elimination by the liver
- has a shorter half-life so given in slow release formula
- passes through BBB, may have central effects
- e.g. propranolol, metaprolol
pharmacodynamics - CVS effect
BP lowering
- reduce CO (decrease HR, & cardiac work)
- negative chronotropic
- renin inhibition (B in juxtaglomerular)
- central of sympathetic drive
- reset baroreceptors to decrease sympathetic drive
- inotropic effects (acutely negative, chronically positive) e.g. beta-blockers good for chronic bad for acute
pharmacodynamics - respiratory effect
- B2 receptor antagonism (bronchoconstriction)
- contraindicated in asthmatics
adverse effects of Beta-blockers
- asthma exacerbation
- hypotension
- bradycardia
- fatigue, impotence, nightmares
- mask hypoglycaemia
- promote vasospasm
drug interactions
verapamil = both have potent negative chronotropic effects
diltiazem = caution, but acceptable
other BP lowering drugs
contraindications
acute HF (as B-blockers acutely reduce inotropy)
asthma
beta blocker in angina
- mechanism and drug example
- decrease HR, cardiac work
- improve symptoms
e.g. metoprolol or atenolol
beta blocker post MI
- mechanism
- decrease arrhythmias
- decrease ventricular rupture
- increased cardiac remodelling
example of beta-blocker given in hypertension
- atenolol
- metoprolol
beta blocker in HF
- mechanism and drug example
- decrease cardiac sympathetic tone
- up-regulation of B receptors
- improve baroreceptor function
- improve LV remodelling
e.g. carvedilol, metoprolol, bisoprolol
