Coadministration of oral levofloxacin with agents that impair its absorption: potential impact on emergence of resistance.

Coadministration of fluoroquinolones (FQs) with divalent or trivalent cation-containing compounds (DTCCs) inhibits FQ absorption. In a case-control study of 46 inpatients receiving oral levofloxacin and DTCCs, patients with a levofloxacin-resistant isolate had been previously exposed to nearly twice as many days of levofloxacin/DTCC coadministration (P = 0.04). There remained a borderline significant independent association between the number of days of coadministration and levofloxacin-resistant culture [adjusted odds ratio (95% confidence interval) = 1.26 (0.98, 1.63); P = 0.07], even after controlling for the length of the levofloxacin course and the duration of hospitalisation prior to initiation of levofloxacin. Efforts should be directed at modifying hospital policies for dosing of levofloxacin and DTCCs to prevent coadministration.