Beta Blockers Flashcards
Beta blocker indications
Hypertension Angina HFailure Arrythmias (AF, A flutter, SVT), rate control Thyrotoxicosis Migraine prophylaxis Anxiety
Mechanism of action
Block beta receptors, notably on cardiac muscle (reduce rate and contractility) and kidneys (stop renin release, stops fluid retention). Note B receptors are Gs linked, increased adenylate cyclase and associated kinases. Mostly B1
Contraindicated in asthma, as block the b2 receptors which cause bronchodilation.
Selectivity of diff beta blockers
B1»>B2: metoprolol, atenolol
B1=B2: propanolol
Mixed (a and B): labetalol, carvedilol
Common beta blockers
Metoprolol: B1, lipid soluble, hepatic
Atenolol: B1, polar, renal excretion
Propanolol: B1 and B2, lipid soluble, hepatic
Carvedilol: B1, B2 and alpha. Antioxidant
Labetalol: B1, B2 and alpha. Pregnancy induced hypertension
Esmolol: broke down in blood, B1. Used in IC as rapidly broken down, but rapid effect
Sotalol: anti-arrythmic, renal excreted.
BETA BLOCKER effects CVS BP; chronotropy; inotropy RESP EYE METABOLIC THYROTOXICOSIS MIGRAINE
BP: unclear, but reduce CO (HR, work); reset baroreceptors, renin inhibtion, reduce sympathetic activity centrally (lipid soluble, cross BBB)
Chronotropy: negative effects, SAN slow, slows AVN conduction
Inotropy: negative if acutely ill. If chronic positive, for chronic stable heart failure improves. DO NOT want to use in acute heart failure, as will reduce inotropy. In acute, diuretics
RESP: B2 receptor antagonism, contraindicated in asthmatics
EYE: reduce aqeous humour production (glaucoma)
Metabolic: decrease glycogenolysis (mask hypoglycaemia)
Thyro: negative chronotropy, decrease T4, less T3
Migraine: unsure, but central mechanism
Beta blocker adverse effects
Resp: asthma exacerbation
CVS: hypotension, acute CCF exacerbation (negative inotrope), bradycardia
Fatigue, impotence, nightmares
Mask hypoglycaemia (decrease sympathetic response when hypo, and prolongs hypo recovery)
Drug interactions
Drug withdrawal: has to titrate BB down, due to increased B receptor upregulation. So sudden stop tachycardia
BBlockers interactions
Never with verapamil, as both negative chronotrope, so bradycardia or heart block.
Must be cautious, but possible with diltiazem as less effect on AVN
Antidiabetics due to hypo mask (with these, more likely to be hypo)
Beta blockers and Angina
First line: Reduces heart ate and cardiac work, improves symptoms
Metoprolol or atenolol
Post MI: decrease chance of arrythmia, decrease chanceof ventricular rupture, increase cardiac remodellling
Beta blockers and heart failure
ratio of b2 and a1 receptors in damaged heart
Mechanism?
CHRONIC, reduced systolic function (systolic heart failure)
Combined therapy with ACEi, diuretic?
Carvedilol, metoprolol or bisoprolol (also B1 selective)
A damaged heart has less B1, more B2 and alpha1 in it.. Chronic beta blockade may increase B1 upregulation and amount, helping chronic HF
-Decrease sympathetic drive, so lower HR, increase filling; up regulate B2 receptors maybe multifactorial.
Beta blockers and hypertension
Atenolol, metoprolol
Unclear how it reduces
2nd/3rd line now
Thyrotoxicosis and migraine and specific beta blockers
Thyro: propanolo, stops T4-T3 conversion, so no tachycardia, agitation, tremor
Migraine: propanolol, atenolol, metoprolol. Central B1?
Scenario: 40y/o with new onset angina, hyperlipidaemia, childhood asthma, HT
Not BB as asthma, diltiazem maybe as rate control properties, as may reduce BP
Scenario: 70 y/o man, with SOB and pulmonary oedema admitted to ED. Hypoxic, fluid overload, chest crackles
Not BB in acute decompensated CCF (no negative inotropes acutely)
Initial: diuretics, O2, nitrates, ACEi, low dose Beta blockade when condition stable
Scenario: 60 y/o anxious HT on bendrofluazide and cilazipril.
What anti hypertensive, warning
Add once daily beta blocker: atenolol, metoprolol. Will reduce anxiety maybe, reduce HR
Warn: fatigue, dizzy, slowing down, erectile dysfunction, enquire asthma, bradycardia
