Beta Blockers Flashcards
Classification of beta blockers
First generation (nonselective
ß-adrenergic blockers)
Propranolol limolol
Pindolol
• Sotalol
Second generation (Bi-selective
adrenergic blockers)
Atenolol®
Acebutolol
Bisoprolol
Esmolol
• Metoprolol
Third generation (B-blockers with additional vasodilatory effect)
Nonselective
• Labetalol
• Carvedilol
B,-Selective
• Betaxolol
• Celiprolol
•
Therapeutic effects of beta blockers?
- Angina prophylaxis and MI: B-Blockers reduce yocardial O2 demand by decreasing heart rate, myocardial contractility and arterial pressure: They improve exercise tolerance and reduce frequency of anginal episodes. Use of ß-blockers early in acute phase of MI may limit infarct size. Long-term use of -blockers may reduce mortality and reinfarction.
- Cardiac arrhythmias: B-Blockers are mainly used in atrial arrhythmias such as atrial fibril-lation, atrial flutter and paroxysmal supraventricular tachycardia (PSVT) but rarely for ventricular arrhythmias (pp. 159-160).
- CCF (see p. 150): Chronic use of -blockers such as carvedilol, metoprolol, nebivolol and bisoprolol has shown to reduce mortality rate in chronic heart failure.
- Pheochromocytoma: B-Blockers are used to control the cardiac manifestations of pheo-chromocytoma, but should not be given alone (see p.101).
- Glaucoma (pp. 70-71): B-Blockers decrease IOP by reducing the production of aqueous hu-mour. Timolol, carteolol, levobunolol, betaxolol, etc. are used topically in glaucoma. Timolol is the most frequently used -blocker in glaucoma. Betaxolol is a selective B,-blocker; hence, systemic adverse effects (cardiovascular and pulmonary) are rare.
Prophylaxis of migraine: Propranolol and metoprolol are
effective in reducing the fre-
quency of migraine headache. The mechanism is not known. - Hyperthyroidism: The signs and symptoms of hyperthyroidism such as tachycardia, pal-pitation, tremor and anxiety are reduced because of blockade of B-receptors. Propranolol inhibits the peripheral conversion of Ta to I3. It is also used in thyroid storm.
- Essential tremors: Oral propranolol may give some benefit in patients with essential
tremors. - Acute anxiety states: B-Blockers are useful in controlling the symptoms of acute anxiety such as palpitation, tachycardia, tremor and sweating.
Alcohol withdrawal: Propranolol may produce some benefit in the treatment of alcohol withdrawal. - Hypertrophic obstructive cardiomyopathy: Propranolol decreases outflow resistance.
- Dissecting aortic aneurysm: B-Blockers are useful in the management of dissecting aortic aneurysm - they decrease cardiac contractility and the rate of development of pressure during systole.
- Prevent variceal bleeding in portal hypertension: Nonselective beta-blockers like nadolol and propranolol are useful. They decrease cardiac output, constrict splanchnic blood vessels → \ portal blood flow → / portal pressure → I risk of variceal
Adverse effect of beta blockers ?
Aaverse effects of -blockers. They are mainly an extension of pharmacological actions.
CVS:
• Bradycardia, heart block and may precipitate congestive heart failure in patients with low-cardiac reserve.
• Blockade of vascular 2-receptors causes unopposed a action, reduces further blood supply and may worsen peripheral vascular disease
• B-Blockers can exacerbate Prinzmetal angina (variant angina) due to unopposed as action, hence are contraindicated (see p. 140) in this condition.
2 Respiratory system: Blockade of Bz-receptors in the bronchial smooth muscle can cause severe bronchospasm in patients with asthma and COPD. Hence, B-blockers are contraindicated in the above conditions.
3. CNS: Sleep disturbances, hallueinations, fatigue and mental depression.)
Metabolic: Recovery from hypoglycaemia (induced by antidiabetic drugs) is delayed by B-blockers. B-Blockers may mask the warning signs and symptoms of hypoglycaemia.
5. Muscular weakness and tiredness: These are due to reduced blood flow to skeletal muscle.
6. Withdrawal symptoms: Abrupt withdrawal of B-blockers after chronic use is dangerous because angina or frank myocardial infarction (MIl) and even sudden death can occur. This is due to upregulation (supersensitivity) of B-receptors in response to prolonged blockade
