Drugs used to Congestive Heart Failure- Cardiac glycosides

Drugs used to Congestive Heart Failure

1. Drugs used in the treatment of Heart failure CARDIAC GLYCOSIDES D r . A b i r a mi

2. Congestive Heart Failure Definition Heart failure is the condition in which the heart is unable to pump sufficient amount of blood to meet the metabolic demands of the body and also unable to receive it.

3. Cardiac Output Stroke Volume Cardiac output : the amount of blood pumped by the heart, in mL/min Stroke volume: the amount of blood pumped out of the heart with each heartbeat cardiac output ( m L/ m in) heart rate (heats/ m in) stroke volume ( m L/heat) Normal stroke volume 50-100ml

4. Actions of the Heart 1. Chronotropy- Heart rate or heart beat Tachycardia- Increases in heart rate Bradycardia- Decreases in heart rate 2. Inotropy- Force of contraction Positive inotropic action- Increases in force of contraction Negative inotropic action- Decreases in force of contraction Dromotropy- Conduction of impulse Positive dromotropic action- Increases in the velocity of conduction Negative dromotropic action- Decreases in the velocity of conduction 4. Bathmotropy- Excitability of cardiac muscle 5.Lusitropy- Rate of myocardial relaxation

5. Heart Failure The therapeutic goal In the treatment of HF is to increase Cardiac output (CO ) Classification 1. Drugs with positive inotropic effects A. Cardiac Glycosides: Digoxin, Digitoxin, Ouabain B. Bipyridines or Phosphodiesterase inhibitors: Inamrinone, Milrinone, Enoximone C. Beta adrenergic agonists: Dopamine, Doputamine, Dopexamine 2. Drugs without positive inotropic effects A. Diuretics : Furosemide, Hydrochlorothiazide, Spiranolactone B. ACEIs: Enalapril, Lisinopril, Ramipril C. AT1 Antagonist: Losartan, Telimisartan D. Beta 1 adrenergic antagonists : Bisoprolol, Carvedilol, Metoprolol E. Vasodilators: Hydralazine, Sodium nitroprusside

6. Cardiac glycosides Source: Leaves of Digitalis lanata, Digitalis purpurea Digitalis lanata (White fox clove) - Digoxin, Digitoxin Digitalis purpurea (Purple Fox clove)- Digitoxin, Gitoxin Seeds of Strophanthus gratus- Stophanthin- G and Ouabain Seeds of Strophanthus kombe- Strophanthin- K

7. Cardiac glycosides Therapeutic uses Digoxin is the most preferred drug amongst the three glycosides. Digitoxin is preferred in the cases having renal impairment. Ouabain is reserved for acute heart failure. Used in the treatment of Heart failure. Paroxysmal supraventricular tachycardia Atrial flutter and atrial fibrillation

8. Cardiac glycosides Adverse effects and management of toxicity Digitalis has cumulative effect and smaller therapeutic window, it is always safer to prescribe a dose that provides digitalis plasma concentrations of 0.8- 2.0ng/ml. 2.5ng/ml is a toxic level. Cardiac side effects : Bradycardia, partial or complete heart block, coupled beats (bigeminy), ventricular fibrillation and fatal cardiac arrythmias. If cardiac arrythmias develop Ca2+, Mg2+ and K+ Status should be corrected For Bigeminy, oral K+ Supplementation and withdrawal of digoxin may be sufficient. If arrythmias are more serious, parenteral K+ and lidocaine may be administered.

9. Cardiac glycosides If the automaticity also get depressed at toxic dose, the patient can be saved by administering digitalis antibodies e.g: Digibind fab fragments (Digitalis immune fab) A 40mg of vial of these antibodies neutralises 0.6mg of digoxin stored in the body. Extra cardiac side effects: Anorexia, vomitting, disrrhoea, headache, neuralgia, blurred vision, loss of color perception, gynacomastia

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