Digitalis induced Ventricular Tachycardia

Q: Which of the following is more effective in Digitalis-induced Ventricular Tachycardia (V.Tach.)? - select one

A) Lidocaine

B) Phenytoin

Answer: B

Ventricular tachycardia (V.Tach.) is common in Digitalis toxicity and may respond well to Phenytoin (Dilantin). Lidocaine is another practical choice, but phenytoin depresses the enhanced ventricular automaticity without significantly slowing AV conduction. Phenytoin may reverse digitalis-induced prolongation of AV nodal conduction. Phenytoin has been shown to dissociate the inotropic and dysrhythmic action of digitalis, thus suppressing digitalis-induced tachydysrhythmias without diminishing the contractile effects. In addition, phenytoin can terminate supraventricular dysrhythmias induced by digitalis, whereas lidocaine may not be as effective.

Phenytoin has been administered in boluses of 100 mg every 5-10 minutes up to a loading dose of 15 mg/kg.

#cardiology

#pharmacology

References:

1. Alvarado-Alvarado JA, Salas-Villela RA, Reyes-Guerrero JA, Ezquerra-Osorio A. Phenytoin as treatment for bidirectional ventricular tachycardia in a patient with anterior myocardial infarction and digoxin toxicity. Arch Cardiol Mex. 2022;92(4):550-552. doi: 10.24875/ACM.21000262. PMID: 36413700; PMCID: PMC9681520.

2. Garan H, Ruskin JN, Powell WJ Jr. Centrally mediated effect of phenytoin on digoxin-induced ventricular arrhythmias. Am J Physiol. 1981 Jul;241(1):H67-72. doi: 10.1152/ajpheart.1981.241.1.H67. PMID: 7246790.

3. O'Reilly MV, MacDonald RT. Efficacy of phenytoin in the management of ventricular arrhythmias induced by hypokalaemia. Br Heart J. 1973 Jun;35(6):631-4. doi: 10.1136/hrt.35.6.631. PMID: 4712468; PMCID: PMC458670.

4. Regina AC, Rehman R, Hai O. Cardiac Glycoside and Digoxin Toxicity. [Updated 2025 Mar 25]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2025 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK459165/