Lecture 11: Beta blockers Flashcards
What are the indications for beta-blocker use?
- Hypertension
- Angina
- HFrEF
- Arrhythmias
- Thyrotoxicosis
- Migraine prophylaxis
- Anxiety
What do the beta receptors do?
BV - Dilation
Bronchi - Relaxation
Kidneys - Renin
Heart - Tachy + Contractility
What drugs have beta subtype selectivity?
B1»>B2
Metoprolol, atenolol, celiprolol, emsolol
B1 = B2
- Propranolol, nadolol
What are the main differences in beta blockers?
Selectivity
- B1 v B2
Elimination
Renal v Liver
Half life
Solubility
- Water v Lipid (shorter T1/2)
What are the commonly used beta blockers and some of their propeties?
Metoprolol
- B1, lipid sol, hepatic
Atenolol
- B1, Polar, renal
Propranolol
- B1/2, lipid, hepatic
Carvedilol and labetalol
- Alpha, B1, B2
How are beta blockers absorbed?
- Oral is good
- Sustained release preps
- Some IV preps (hypertensive emergencies)
Describe the distribution / metabolism of beta blockers:
Variable lipophilicity
- Propranolol, metoprolol (high) and liver metab.
- Atenolol (low), renal excreted.
Lipophilicity = crosses BBB
Whats the PK of beta blockers?
Lipophilic
- Propranolol, metoprolol
- Extensive rapid gut absorption
- First pass
- Enters BBB
- High protein binding
Hydrophilic
- Atenolol
- Renal excretion
- Longer T1/2
Whats the effects of beta blockers on lowering BP?
Lowers BP
- Unsure of mechanism
- Reduced CO, HR an cardiac work
- Resets baroreceptors
- Renin inhibition
- Central actions (Dec. SNS)
- Decrease TPR
How do beta blockers effect chronotropy? and inotropy?
-ive chronotrope
- SA node effects
- AV node transmission
-ive inotrope (acute short term)
+ive inotrope (long term)
Why are beta blockers contraindicated in heart failure?
B/C the SNS is trying to enhance CO.
So must use diuretic to find euvolemic stable state before considering beta blocker.
How do beta blockers act in resp. eye and gut?
Resp
- B2 antagonism
- Contraindicated in asthmatics
Eye
- Reduces aqeous humor prod (topical app)
Metabolic
- Dec glycogenolysis (attenuate hypoglyceamia)
How do beta blockers function in thyrotoxicosis? and some examples:
- Negative chrontropic
- Prevents T4-T3 conversion
= Propranolol
What are the adverse effects of beta blockers?
Resp
- Asthma exacerbation
CVS
- Hypotension, bradycardiac, acute CCF exacerbation (-ive inotrope), promote vasospasm
- Fatigue, impotence, nightmares.
- Mask hypoglycemaia
- Drug withdrawal (tachy and tremors, must titrate dose down)
What are some drug interactions of beta blockers?
- Verapamil (C/I) Marked -ive inotrope effect
- Diltiazem (Cautioned)
- Other blood pressure lowering drugs and antidiabetic drugs *hypoglyceamia awareness
