Blockers Toxicity Mechanism of Action Used for ttt

β-Blockers Toxicity

Mechanism of Action - Used for ttt of hypertension , coronary heart disease , arrhythmia and migraine. 1 - β-adrenergic receptors : β-1 receptors primarily regulate myocardial tissue and affect the rate of contraction. β-2 receptors regulate smooth muscle tone and influence vascular and bronchiolar relaxation. 2 - They decrease adenylate cyclase and c. AMP and leads to decreased influx of sodium and calcium ions and produce negative inotropic and chronotropic effects 3 - Membrane Stabilizing Activity (MSA): quinidine like action Fast Na-Channel inhibition wide QRS 4 - Lipophilicity: Cross BBB into CNS Seizures and CNS depression

Clinical Presentation 1 - Hypotension and bradycardia are common. Arrythmias and prolongation of PR interval with AV block and QRS interval prolongation. Cardiogenic shock and asystole in severe overdose. 2 - Seizures , coma , respiratory depression or arrest. 3 - Hypoglycemia may occur (by inhibiting glycogenolysis) (β 2) 4 - Hyperkalemia 5 - Bronchospasm in asthmatic patients

Investigations 1 - ECG: 2 - Serum electrolyte especially K level 3 - Serum glucose 4 - Arterial Blood gases (ABGs) 5 - Renal function tests Treatment I- Emergency measures ABCD II- GIT decontamination: beneficial if done within 1 -2 hours of ingestion. Atropine before lavage to avoid severe bradycardia -AC is given routinely after lavage III- Antidote (Glucagon) -Increase inotropic and chronotropic effects through a non-adrenergic mechanism. It activate myocardial adenylate cyclase …. Increase c. AMP and cardiac cotractility - Dose: 50 μg/kg IV bolus over 1 -2 minutes followed by an infusion of 1 -5 mg / hour

IV- Fluids for hypotension -Atropine : if fluids therapy fails -Benzodiazepines for convulsions D. D Ca-channel blockers 1 - Ca channel blockers block Ca channels of vascular smooth muscles and cardiac muscles. Used in ttt of hypertension and angina 2 - Acute toxicity is similar to β-Blockers … Hyperglycemia 3 - TTT as β-Blockers : Ca chloride 10% 10 -20 ml slowly IV should be given for hypotension and myocardial depression.