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Cytochrome P450-Mediated Interactions: In vitro studies with cytochrome P450 isoenzymes (CYP) have shown that moxifloxacin does not inhibit CYP3A4, CYP2D6, CYP2C9, CYP2C19, or CYP1A2, so it is unlikely to alter the pharmacokinetics of drugs metabolized by these enzymes. Cytochrome P450 isoenzymes are also not known to be involved in the metabolism of moxifloxacin. Based on these results, metabolic interactions via cytochrome P450 enzymes are unlikely to occur.
Clinical studies indicate no interactions when moxifloxacin is administered with ranitidine, probenecid, oral contraceptives, calcium supplements, parenterally administered morphine, theophylline, cyclosporine, or itraconazole.
Rifampicin: When given with a double dose of rifampicin, the AUC (Area Under the Curve) of moxifloxacin decreased by approximately 30%. The clinical consequences of this are unknown, and no dose adjustments are recommended when used together.
Rifapentine: When given with a double dose of rifapentine, the AUC of moxifloxacin decreased by 17%. The clinical consequences of this are unknown, and no dose adjustments are recommended when used together.
Drugs that Prolong the QT Interval: The additive effect on QT interval prolongation of moxifloxacin and other drugs that prolong the QT interval cannot be ignored, for example: Class IA antiarrhythmic drugs (e.g., quinidine, hydroquinidine, disopyramide).
Class III antiarrhythmic drugs (e.g., amiodarone, sotalol, dofetilide, ibutilide).
Neuroleptics (e.g., phenothiazine, pimozide, sertindole, haloperidol, sultopride).
Tricyclic antidepressants.
Certain antimicrobials (sparfloxacin, erythromycin IV, pentamidine, antimalarials, especially halofantrine).
Certain antihistamines (terfenadine, astemizole, mizolastine).
Others (e.g., cisapride, bepridil).
This effect may increase the risk of ventricular arrhythmias, particularly torsades de pointes.
Therefore, moxifloxacin is contraindicated in patients treated with these drugs.
Bivalent and Trivalent Cations: Chelating agents such as iron, aluminum, and magnesium can inhibit the absorption of moxifloxacin. Co-administration or administration of drugs containing these cations with moxifloxacin can reduce its exposure by approximately 25-60%. A minimum separation of 6 hours between the administration of drugs containing bivalent or trivalent cations (e.g., magnesium or aluminum-containing antacids, didanosine, sucralfate, and iron or zinc-containing medications) and moxifloxacin is recommended. Calcium does not affect moxifloxacin exposure, and calcium-containing supplements can be taken with moxifloxacin.
Changes in INR (International Normalized Ratio): A significant number of cases have reported increased oral anticoagulant activity in patients receiving antibiotics, especially fluoroquinolones, macrolides, tetracyclines, cotrimoxazole, and some cephalosporins. It is difficult to evaluate whether infection or antibiotic therapy is the cause of the INR disturbance. INR should be closely monitored in patients receiving warfarin or other anticoagulants.
Food Interactions: Moxifloxacin has no clinically relevant interactions with food, including dairy products.
Warfarin: No interaction was observed with warfarin in terms of prothrombin time and other coagulation parameters when used concomitantly.
Digoxin: The pharmacokinetics of digoxin are not affected by moxifloxacin (and vice versa).
Antidiabetic Medications: No clinical interaction was observed between glibenclamide and moxifloxacin.
