Drug Interactions between Avelox and didanosine

ADJUST DOSING INTERVAL: Concomitant administration with didanosine buffered tablets or pediatric oral solution may reduce the oral bioavailability of moxifloxacin and other quinolone antibiotics. The mechanism is reduced quinolone absorption due to chelation with metallic cations from buffering agents and antacids used in certain formulations of didanosine. In 12 healthy volunteers, administration of an antacid containing aluminum hydroxide-magnesium hydroxide (900 mg-600 mg/10 mL dose) 4 hours before, simultaneously, and 2 hours after a single 400 mg dose of moxifloxacin reduced the relative bioavailability of moxifloxacin by 23%, 60%, and 26%, respectively. The pharmacokinetics of moxifloxacin have not been studied in combination with the various didanosine formulations, but significant reductions in bioavailability have been reported for ciprofloxacin, another quinolone, in interaction studies with didanosine.

MANAGEMENT: Moxifloxacin should be administered at least 4 hours before or 8 hours after didanosine buffered tablets or pediatric oral solution, and patients should be monitored for potentially decreased antimicrobial efficacy during concomitant therapy. Didanosine buffered powder for oral solution, which uses a citrate-phosphate buffer, and the delayed-release capsules, which are not buffered, are not expected to cause this interaction.