lanoxin and Invirase Interactions

Interactions between lanoxin(digoxin) and Invirase (saquinavir)

digoxin and saquinavir (Major Drug-Drug)

MONITOR CLOSELY: Coadministration with saquinavir may significantly increase the serum concentrations of digoxin. The mechanism of interaction has not been described but may be related to saquinavir inhibition of the P-glycoprotein-mediated renal tubular secretion of digoxin. In 16 healthy volunteers, administration of a single 0.5 mg dose of digoxin with saquinavir/ritonavir (1000 mg/100 mg twice a day for 16 days) resulted in a 27% increase in digoxin peak plasma concentration (Cmax) and a 49% increase in systemic exposure (AUC). Increases in serum digoxin concentration were greater in female subjects than in male subjects.

MANAGEMENT: Caution is advised if digoxin must be used concurrently with saquinavir. Serum digoxin levels should be checked frequently and the dosage adjusted accordingly, particularly following initiation or discontinuation of saquinavir in patients who are stabilized on their digoxin regimen. Patients should be advised to notify their physician if they experience signs of digoxin toxicity such as nausea, anorexia, visual disturbances, slow pulse, or irregular heartbeats.