Drug Interaction Report

Coadministration of topical lidocaine with class III antiarrhythmics (e.g., amiodarone, dofetilide, sotalol) may lead to additive cardiovascular effects. Drug interaction studies evaluating class III antiarrhythmics with topical lidocaine formulations are unavailable. The degree of systemic absorption of topical lidocaine may be dependent on the duration of application and the applied surface area. Some authorities recommend increased clinical monitoring during concomitant use.

In vitro data suggest that grapefruit juice may inhibit the CYP450 3A4 first-pass metabolism of dofetilide. Decreased first-pass metabolism may increase dofetilide concentrations and increase the risk of QT interval prolongation and arrhythmias. The clinical significance is unknown, since dofetilide has a high oral bioavailability and a low affinity for CYP450 3A4. The manufacturer recommends caution.