phenytek and Tikosyn Interactions

Interactions between phenytek(phenytoin) and Tikosyn (dofetilide)

phenytoin and dofetilide (Major Drug-Drug)

CONTRAINDICATED: Dofetilide should not be used with Class I or other Class III antiarrhythmic agents due to the potential for additive effects on myocardial refractoriness. Many of these agents, including dofetilide, can also cause prolongation of the QT interval, thus concomitant use may increase the risk of ventricular arrhythmias such as ventricular tachycardia and torsade de pointes.

MANAGEMENT: Class I (e.g., disopyramide, quinidine, procainamide) and class III (e.g., amiodarone, ibutilide, sotalol) antiarrhythmic agents should be withheld for at least 3 half-lives before administering dofetilide. In the case of amiodarone with its unpredictable pharmacokinetics, dofetilide should not be initiated until serum amiodarone levels are below 0.3 mcg/mL or amiodarone has been withdrawn for at least three months.