Effects of high-dose cancer chemotherapy on the absorption of digoxin in two different formulations

The oral absorption of digoxin in tablet form has been reported to be reduced after cancer chemotherapy and radiation therapy because of cancer treatment-induced damage to the intestinal epithelium. We investigated possible differences in the effects of high-dose cancer chemotherapy on the relative bioavailability of digoxin administered in tablet form (Lanoxin; Burroughs Wellcome Co.) and in solution-in-capsule form (Lanoxicaps; Burroughs Wellcome Co.). Each subject received a single oral dose of either 0.5 mg Lanoxin (six subjects) or 0.4 mg Lanoxicaps (seven subjects) both before and after chemotherapy. For Lanoxin, there was a significant reduction in the AUC after chemotherapy to 54.4% +/- 35.5% (mean +/- SD) of the value before chemotherapy (P = 0.02), whereas for Lanoxicaps there was an insignificant reduction in AUC to 85.1% +/- 42.7% of the value before chemotherapy. These findings show that changes in the oral dosage formulation of digoxin from a tablet to a solution-in-capsule form can overcome the adverse effects of high-dose cancer chemotherapy on drug absorption, and suggest a similar approach may be successful for other drugs.