Digitalis Drugs: Dose, Action, side effects and Contra-indications

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Digitalis drug is used in the treatment of Congestive cardiac failure, Left ventricular failure, Arterial fibrillation and flutter, premature beats and Supra-ventricular tachycardia.

Dose of Digitalis Drugs

  1. Rapid
    1. Digoxin 1.5 mg : initially 0.5 mg 6 hrly till digitalization
    2. Digoxin 0.4 mg : orally0.2 mg.6 hrly till digitalization
    3. Ouabain : I.V. ultra-short acting
  2. Slow
    1. Digoxin 0.25 - 0.5 mg : initially 0.25 mg/day till digitalization.
    2. Digitoxin 0.2 mg : initially 0.2 mg. 8 hrly till digitalization.
  3. Maintenance dose
    1. Digoxin 0.25 mg/day : 10-20 μgm/kg body wt
    2. Digitoxin 0.1-0.2 mg/d

Action of Digitalis

  • It increases the force of Systolic contraction and decreases the oxygen expenditure for a given work output.
  • Heart rate is decreased.
  • Conduction through the A.V. node and Purkinje's fibers is depressed.
  • Refractory period of atria and ventricles is decreased and that of AV node is increased (QT interval shortens). It acts by inhibiting the sodium-potassium ATPase. This causes faster release of calcium which enhances the automaticity, contractibility ectopic pacemaker activity.
  • It is a cardiac glycoside. It works by correcting irregular heartbeat to a normal rhythm and increases the force with which the heart muscle contracts with every heartbeat.

Common side effects of Digitalis

  • Cardiac: Premature beats atrial and ventricular tachycardia and fibrillation. Heart blocks, sinus bradycardia, Arrhythmia (irregular heartbeats)
  • Gastrointestinal: Anorexia, nausea, vomiting (of central origin} and diarrhea.
  • Neurological: Vertigo, Visual hallucinations, color vision defects and blurring, Headache, Neuralgic pains.
  • Miscellaneous: Skin rashes (Eosinophilia), Dizziness, Gynecomastia, Premature labour with ECG changes in fetus and Visual impairment

Contra-indications of Digitalis

  • High output states
  • Partial heart (AV) block
  • Ventricular tachycardia
  • Constrictive pericarditis
  • Myocarditis/Diphtheria
  • Hypersensitivity
  • WPW syndrome
  • Hypokalemia

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