Which combination of drugs could interact adversely with Warfarin?

• A. Fluconazole and Levofloxacin
• B. Phenobarbital and Daptomycin
• C. Metronidazole and Rifampin
• D. Ampicillin and Erythromycin

Answer: (A)

The correct combination that could interact adversely with Warfarin is Fluconazole and Levofloxacin due to the potential for increased anticoagulant effects when taken together.

Fluconazole is an azole antifungal that can inhibit the metabolism of Warfarin by affecting the cytochrome P450 enzyme system, specifically CYP2C19 and CYP3A4. This inhibition can lead to elevated levels of Warfarin in the bloodstream, increasing the risk of bleeding.

Levofloxacin, a fluoroquinolone antibiotic, is also known to have a variable effect on Warfarin, as it can enhance the anticoagulant effect by mechanisms that may involve alterations in gut flora or direct effects on bleeding risk.

The other combinations listed do not notably possess the same potential for significant interactions that would lead to increased anticoagulation or bleeding risks when taken with Warfarin. Therefore, the combination of Fluconazole and Levofloxacin is particularly noteworthy for clinicians monitoring patients on anticoagulation therapy.