This document discusses β-adrenergic blockers (β-blockers), which are effective in treating several cardiovascular conditions like angina, arrhythmias, hypertension, and congestive heart failure. It covers the classification of β-blockers based on their selectivity, intrinsic sympathomimetic activity, lipid solubility, and ability to block alpha receptors. The main pharmacological effects and clinical uses of β-blockers are reducing heart rate and contractility, lowering blood pressure, and decreasing intraocular pressure for glaucoma. Adverse effects can include bradycardia, bronchospasm, fatigue, and sexual dysfunction.
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L7 ans pharmacology 17 18
1. Drugs Affecting
The Autonomic Nervous System(ANS)
β-Adrenergic Blockers
ANS Pharmacology
Lecture 7
Dr. Hiwa K. Saaed
College of Pharmacy/University of Sulaimani
2017-2018
2.
3. β-Adrenergic Blockers
• β-Blockers are effective in treating:
• angina,
• cardiac arrhythmias,
• myocardial infarction,
• congestive heart failure,
• hyperthyroidism,
• and glaucoma,
• as well as serving in the prophylaxis of migraine headaches.
• Note: The names of all β-blockers end in “olol” except for labetalol and carvedilol.
• All are competitive antagonists
• Propranolol is prototype
• Although all β-blockers lower blood pressure in hypertension, they do not induce
postural hypotension!? because the α-adrenoceptors remain functional.
6. 2, Combined (α & β): peripheral vasodilation
Labetalol & Carvedilol
• Useful in Rx HTN patients for whom increased Peripheral resistance is
undesirable (elderly or black)
• Labetalol in Rx preeclampsia, pheochromocytoma
• They do not alter serum lipid or blood glucose levels
• Carvedilol also decreasees lipid peroxidation and vascular wall thickening
(benefit in heart failure)
7. 3. Partial agonist activity ISA
Pindolol, Acebutolol & Labetalol
less bradycardia & diminished effect on CO,
less disturbances of lipid and carbohydrate metabolism
Advantages:
• HTN with asthma,
• HTN with moderate bradycardia
• HTN+DM
4. Local anesthetic activity (membrane-stabilizing activity):
Is a disadvantage when used topically in the eye because it decreases protective
reflexes and increases the risk of corneal ulceration
Timolol, atenolol, carvedilol & nadolol: no Local anesthetic activity
9. 6. K+ channel blockade: sotalol
• Sotalol is a nonselective β receptor antagonists,
• that lack Local Anesthetic action
• but has marked class III antiarrhythmia effect reflecting k+ channel
blockade
10. B. Pharmacological Effects and Clinical Uses
1. CVS:
A. Heart: both
• decreased HR, force of contraction (–ve inotropic & chronotropic effect)
• decreased A-V conduction, ↑PR interval
• Decrease CO, work & O2 consumption
Rx: Angina and Supraventricular tachycardia
B. Vascular system: prevent β2 mediated vasodilation→ reduction in CO
(because of cardiac effect) → decrease BP → reflex vasoconstriction.
On balance there is gradual reduction of both systolic and diastolic BP
11. 2. Respiratory: bronchoconstriction; contraindicated in asthma
3. Eye: reduce IOP especially in Glaucomatous eyes decrease aqueous humor
production
4. metabolic and endocrine effects:
A. Increased Na+ retention, how?
• Reduced BP causes a decrease in renal perfusion, resulting in an increase in Na+
retention and ↑plasma volume → In some cases, ↑BP.
• For these patients, β-blockers are often combined with a diuretic to prevent Na+
retention.
• Also by inhibiting β receptors, renin production is also prevented, contributing to
Na+ retention.
B. Pharmacological Effects and Clinical Uses
12. B. inhibit lipolysis: ↑ plasma VLDL, ↓ HDL,─LDL
↓ HDL/LDL ratio→ coronary heart disease
C. partially inhibit glycogenolysis and decrease glucagon secretion
Great caution in IDDM (Type 1)?
Because pronounce hypoglycemia may occur after insulin injection, β blockers also
attenuate the normal physiologic response to hypoglycemia, furthermore they
mask signs of hypoglycemia; tremor, palpitation..
4. metabolic and endocrine effects:
13. B. Pharmacological Effects and Clinical Uses
Cardiovascular and ophthalmic applications are extremly important
A. CVS:
-angina pectoris ↓cardiac work & O2 demand,
-Chronic hypertension, ↓CO, ↓ TPR, inhibition of renin release
NB: β blockers are not used for acute or emergency Rx of HTN,? may increase diastolic pressure
Labetalol is effective in emergency HTN
-Arrhythmia (supraventricular tachycardias),
-prophylaxis after MI:
1) early use within 6-12 hrs for 3-4 wks
2) Late use within 4 days- 4 wks after onset of infarction and continued for at least 2 years useful for secondary
prevention from another MI
- congestive heart failure*
14. B. Eye: Glaucoma: reduce aqueous humor secretion (timolol)
C. Endocrine use: Thyroid storm, thyrotoxicosis: propranolol
D. CNS: propranolol
1. Anxiety with somatic symptoms
2. Migraine headache prophylaxis:
3. Famillial tremor, other types of tremor, “stage fright”:
4. Alcohol, opioids acute withdrawal symptoms
B. Pharmacological Effects and Clinical Uses
15. C. Adverse effects
• CVS: bradycardia, A-V blockade, CHF
• Arrhythmias: never stop Rx with β blockers suddenly
• Bronchoconstriction: Patients with airway disease: asthmatic attack
• Sexual dysfunction?? Independent of β blockade
• CNS effects: sedation, fatigue, sleep alterations