Quinolones

Abstract

Fluoroquinolone (FQ) antimicrobials are among the most commonly used agents in the outpatient and institutional patient care environments. Due to this high frequency of utilization, the potential for deleterious drug-drug interactions with non-antimicrobials is also high. The majority of interactions with the FQs involve deleterious effects on the FQ component. These are also the most clinically important interactions with these agents. Multivalent cations such as Mg²⁺, Ca²⁺, Fe²⁺, Zn²⁺, Al³⁺, and other minerals as well as drugs such as sucralfate, lanthanum, sevelamer, and didanosine (the cation-supplemented version of the latter) can substantially reduce FQ bioavailability, leading the subtherapeutic drug concentrations at the infection site and clinical failure. Separation of dose administrations may or may not reduce the magnitude of these interactions. Ciprofloxacin, norfloxacin, and three less widely available FQs (antofloxacin, nemonoxacin, and prulifloxacin) act as moderate cytochrome P450 enzyme inhibitors and may increase serum concentrations of theophylline and caffeine. Warfarin pharmacodynamics are variably affected by the FQs. The pharmacodynamic interactions between NSAIDs and FQs are only relevant if fenbufen is used concurrently with possibly, prulifloxacin. Caution is warranted if FQs are used concurrently with other medications prolonging the QTc interval or if patients have other risk factors for prolongation of the QTc interval (e.g., abnormally prolonged QTc interval pretreatment, electrolyte abnormalities, use of starvation-liquid diets, or history of heart disease). Fluoroquinolone antimicrobials can be used effectively and safely in the vast majority of patients if the clinician remembers those few drug-drug interactions that are clinically important.