Beta blockers Flashcards
Indications for Beta blockers
HTN Angina HF Arrhythmia Thyrotoxicosis Migraine prophylaxis Anxiety
Name three locations beta one receptors are found and what blocking them does
Heart. Reduces rate and contractility
Kidneys. Reduces renin release
Adipocytes. Inhibit lipolyis
Name three locations Beta 2 receptors are found and what blocking them does
Blood vessels. Vasoconstriction
Bronchi. Bronchioconstriction
Kidneys. Reduces renin release and reduces tubular Na+ reabsorption.
Name a mainly beta 1 selective BB
Metoprolol
How do BB lower BP?
Not totally clear, multifactorial.
Reduces CO (B1 receptors in heart).
Reset carotid baroreceptors reducing sympathetic drive.
Renin inhibition.
Cardiovascular effects of BB
Negative chronotrope
Negative inotrope in acute settings
Positive inotrope chronic setting
Would you give acute HF patient BB?
NO! Contraindicated.
Stabilze with diuretics and O2. Introduce beta blocker after 1/52
Respiratory contraindication
Asthma (not COPD). B2 receptor in lungs, BB can cause bronchioconstriction.
Metabolic effects of BB
Block SNS causing glyconeogenolysis so can prolong hypo in diabetics
How can BB be used in thyroid rx.
Can reduce symptoms of hyperthyroidism as block conversion of T4 to T3
Discuss drug withdrawl with BB
Because of upregulation of B receptors when BB used if abruptly stopped adrenergic effects on b-receptors exacerbated.
Which Ca2+ blocker is contraindicated with BB
Non-DHP (verapamil) as may cause heart block with two negative chronotropes
How does BB improve angina
Reduce HR
Reduce inotropy
How does BB help treat MI
Decrease arrhythmia, decrease ventricular remodelling, increase cardiac modelling
How do BB work to treat chronic HF
Mechanism unclear?
?Upregulation of B1 receptors in heart
?Decrease cardiac sympathetic tone, decrease HR, increase diastolic filling, decrease O2 consumption.
