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Beta
Blockers
- Block beta-adrenergic
receptors, hence decrease heart rate and cardiac output
- Selective beta-blockers have actions chiefly on the heart rate (beta-1
receptors)
- Non-selective
- Propranlol Selective
- Atenolol, Metoprolol
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Atenolol
- Selective
beta-1 receptor blocker
- Decreases heart rate (negative chronotrophic action)
- Decreases myocardial contractility (negative ionotrophic effect)
- Decreases cardiac work load
- Useful in IHD
- Decreases cardiac output
- Useful in hypertension
- Decreases conduction
- Useful in arrhythmias
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Atenolol In
Hypertension
- Negative
chronotropic & inotropic action ----> decreases cardiac output
- Decreases renin activity
- Usual dosage 25-100 mg O. D.
- No adverse effects on foetus; suitable for hypertension in pregnancy
/ pre-eclampsia
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Atenolol
In IHD
- Decreases
cardiac work load ----> decreases O2 requirement
- Decreases contractility, heart rate ----> decreases diastolic filling
time ----> decreases coronary blood flow
- 50-100 mg daily improves exercise capacity, prevents anginal attacks,
reduces nitroglycerin requirements
- After myocardial infarction, atenolol administration prevents further
damage
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Pharmacokinetics
- Absorbed
from G. I. Tract (50%)
- Peak plasma levels : 2-4 hours
- Half life : 6-8 hours (Propranolol : 3-5 hours)
---> once daily dosing
- Crosses placenta is excreted in breast milk
- Does not significantly cross blood brain barrier
- Excreted unchanged in urine/stools
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Other uses
- Arrhythmias
- Alcohol withdrawal
- Hyperthyroidism
- Migraine
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Tolerability
- Well tolerated
- Selectivity of action
- Headache, dizziness, fatigue, bradycardia, cardiac failure
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Advantages
over Propranolol
- Atenolol
is selective; propranolol is a non selective beta blocker. Thus adverse
effects related to beta-2 receptor blockade (e.g., bronchospasm) are
avoided
- Once daily dosing convenience with atenolol
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Salient Features
- Selective
beta-1 receptor blocker
- Beta-1 receptor blockade results in lower myocardial contractility
and heart rate
- Decreased cardiac output and blood pressure; useful in hypertension
- Decreased conduction; useful in arrhythmias
- Well absorbed orally, convenient once daily administration
- Better tolerated than non-selective beta-blockers; can be administered
to asthmatics
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