2/21/2023 0 Comments Beta blocker antidote glucagon moa![]() ![]() Mechanism of action: partial agonist activity.Intrinsic sympathomimetic activity ( ISA) A rule to remember the main effector organs for β receptors: There is 1 heart ( β 1 blockers act on the heart) and 2 lungs ( β 2 blockers affect bronchial smooth muscles). ![]() Inhibits lipoprotein lipase → ↑ triglycerides and ↓ HDL → hyperlipidemiaīeta blockers competitively inhibit adrenergic substances (e.g., adrenaline, noradrenaline ) at β receptors.↓ Hepatic glycogenolysis → hypoglycemia (esp.↓ Glucose uptake ( ↓ insulin sensitivity).↓ Insulin release → hyperglycemia and new-onset diabetes.↓ Aqueous humor production → ↓ intraocular pressure.β 1 blockade of the juxtaglomerular cells → ↓ renin release → ↓ angiotensin II conversion → ↓ H 2O resorption → ↓ BP.Antiarrhythmic effect: β 1 blockade → ↓ AVN conduction, ↑ AVN refractory time, and ↓ heart rate → anti-arrhythmic effect.Anti- ischemic effect: β 1 blockade → ↓ heart rate and ↓ cardiac contractility → ↓ blood pressure (BP) and ↓ oxygen consumption by the heart → anti- ischemic effect.Except for beta blockers with alpha-blocking action ( labetalol, bucindolol, carvedilol), all noncardioselective beta blockers begin with the letters N to Z ( B 2 = second half of the alphabet). With the exception of nebivolol, all cardioselective beta blockers begin with the letters A to M ( B 1 = first half of the alphabet). Esophageal variceal bleeding (prophylactic use).Pregnancy-induced hypertension (e.g, labetalol).Same as side effects of nonselective beta blockers (both with and without ISA).Improve endothelial function and vascular remodeling.Reduce portal hypertension and pressure gradient in hepatic venous.Because of their α-blocking action : vasodilation → ↓ peripheral vascular resistance, ↓ preload, ↓ afterload, and ↑ renal blood flow.Alternative to cardioselective beta blockers.Vasoconstriction: avoid in patients with peripheral vascular disease.Bronchoconstriction : may exacerbate asthma / COPD.Sotalol also blocks cardiac potassium channels (antiarrhythmic effect).Nonselective beta blockers (β 1, β 2, and β 3 receptors) Cardiac arrhythmias (e.g., atrial fibrillation, atrial flutter, PSVT).Generally do not interfere with glycogenolysis safe in diabetic patients.Generally do not cause bronchoconstriction or vasoconstriction.Cardioselectivity is dose-dependent: β 2 receptor blocking activity increases with higher doses.Nebivolol is the only beta blocker that causes NO-mediated vasodilation: it decreases vascular resistance by stimulating β 3 receptors and activating NO synthase in the vasculature.Decrease the heart rate, contractility, and AVN conductivity. ![]()
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