For the following substances absence of a clinically relevant interaction with Avelox has been proven:

• antidiabetics (glibenclamide)
• atenolol
• calcium supplements
• digoxin
• itraconazole
• morphine
• oral contraceptives
• probenecid
• ranitidine
• theophylline.

Avelox does not demonstrate pharmacokinetic interactions with drugs undergoing cytochrome P450 metabolism.

In addition, absorption of Avelox is not altered by food intake (including dairy products).

Antacids, minerals, and multivitamins
Concomitant ingestion of Avelox together with antacids, minerals, and multivitamins may result in impaired absorption of Avelox after oral administration due to formation of chelate complexes with the multivalent cations contained in these preparations. This may lead to plasma concentrations considerably lower than desired. Hence, antacids, anti-retroviral drugs (e.g. didanosine), and other preparations containing magnesium or aluminum, sucralfate and agents containing iron or zinc should be administered at least 4 hours before or 2 hours after ingestion of an oral Avelox dose.

Warfarin
No interaction during concomitant treatment with warfarin on pharmacokinetics, prothrombin time and other coagulation parameters has been observed.

Changes in the International Normalized Ratio (INR): cases of increased anticoagulant activity have been reported in patients receiving anticoagulants concurrently with antibiotics, including Avelox. The infectious disease (and its accompanying inflammatory process), age and general status of the patient are risk factors. Although an interaction between Avelox and warfarin was not demonstrated in clinical trials, INR monitoring should be performed and, if necessary, the oral anticoagulant dosage should be adjusted as appropriate.