Drug Interaction Report

MONITOR CLOSELY: Coadministration of landiolol with positive inotropes, vasoconstrictors, or sympathomimetic agents may decrease the therapeutic effects of landiolol. According to the package labeling, concomitant use reduced landiolol's heart rate and blood pressure lowering effects. In addition, concomitant dobutamine also reduced landiolol's effect on PR-interval prolongation.

MANAGEMENT: If coadministration is clinically necessary, careful titration of the landiolol infusion and close hemodynamic monitoring is advised. Consultation with package labeling and relevant institutional protocols may be advisable for further guidance.

Administration of digoxin with a high-fiber meal has been shown to decrease its bioavailability by almost 20%. Fiber can sequester up to 45% of the drug when given orally. Patients should be advised to maintain a regular diet without significant fluctuation in fiber intake while digoxin is being titrated.

Grapefruit juice may modestly increase the plasma concentrations of digoxin. The mechanism is increased absorption of digoxin due to mild inhibition of intestinal P-glycoprotein by certain compounds present in grapefruits. In 12 healthy volunteers, administration of grapefruit juice with and 30 minutes before, as well as 3.5, 7.5, and 11.5 hours after a single digoxin dose (0.5 mg) increased the mean area under the plasma concentration-time curve (AUC) of digoxin by just 9% compared to administration with water. Moreover, P-glycoprotein genetic polymorphism does not appear to influence the magnitude of the effects of grapefruit juice on digoxin. Thus, the interaction is unlikely to be of clinical significance.