Drugs Used In CCF

Question 1

Classification

Answer 1

1. Diuretics - loop, thiazides, aldosterone antagonists.
2. Vasodilators :
   a. Ace inhibitors, arb’s, direct renin inhibitor, sodiumnitroprusside.
   b. Venodilators - nitroglycerin, isorbide
   c. Arteriolar dilators - Hydralazine, nicorandil.
3. Beta adrenergic blockers
4. Sympathomimetic amines - dopamine
5. Cardiac glycosides- digoxin

Question 2

Cardiac glycosides

Pharmacological actions

Answer 2

Cardiac :
1. Myocardial contractility - positive inotropic effect. Causes complete emptying of ventricles and increases CO. Cardiotonic.

2.Heart rate : negative chronotropic effect. In toxic doses, increases HR.

3. Electrophysiological actions - decreases automacity, increases RMP, prolongs ERP, decreases conduction velocity in AV node.
   In toxic dose - arrthymias.
4. ECG : prolongation of p-r interval, inversion pf t wave, depression of st segment.

Question 3

Extracardiac actions

Answer 3

1. GIT - anorexia, nausea, vomiting, diarrhoea.
2. Kidney - diuresis
3. CNS - confusion, blurring of vision, disorientation.

Question 4

Pharmacokinetics

Answer 4

Oral route.
Food delays absorption.
Concentrated in heart, liver, kidney, skeletal muscle.
Crosses BBB.
Excreted unchanged in urine
Dosage adjustment in renal failure.

Question 5

Adverse effects

Answer 5

1. Cardiac- any type of arrhythmias, ventricular premature beats, pulsus bigeminy, ventricular tachycardia.
   AV block, atrial tachycardia, atrial fibrillation, atrial flutter, severe bradycardia.

Question 6

Factors affecting digitalis toxicity

Answer 6

1. Age - elderly more susceptible
2. Route- iv has more risk
3. Hypokalaemia enhanced toxicity
4. Hypercalcaemia and hypomagnesaemia
5. Hypothyroidism, hyperthyroidism, hypoxia, RF, myocarditis.

Question 7

Treatment of digoxin toxicity

Answer 7

1. Shift to ICU
2. Stop digoxin and potassium depleting diuretics
3. Potassium chloride given orally or iv when serum k level is low/normal.
4. Supra ventricular arrthymias treated with oral or iv propranolol.
5. IV lignocaine for ventricular arrhythmias.
6. Atropine and cardiac pacing for AV block, bradyarrthymias.
7. Digoxin antibodies- digibind for serious digitalis toxicity.

Question 8

Drugs interactions of digoxin

Answer 8

1. Cholestyramine + digoxin - cholestyramine bind to cardio glycosides in gut and reduce absorption.
2. Beta-blockers + digoxin - have additive depressant effect on SA and AV nodes.
3. Thiazides + digoxin - Hypokalaemua caused by diuretics may potentiate digoxin therapy.
4. Calcium + digoxin - ca increases the incidence of digoxin toxicity.
5. Digoxin + symphathomimetic - chances of cardiac arrhythmias are mire with sympathomimetic in patients on digoxin.

Question 9

Therapeutic uses of digoxin

Answer 9

1. CCF - in patients with low output failure when esp associated with atrial fibrillation.
2. Atrial fibrillation- direct and indirect effect on AV node. Depresses av node by increasing ERP and decreasing conduction velocity this reduces ventricular rate.
3. Paroxysmal supra ventricular tachycardia: digoxin has a slower onset of action, hence not suitable for Acute therapy.