The relative oral bioavailabilities of ciprofloxacin and ofloxacin when they were coadministered with water or an enteral feeding product (Ensure) were assessed in 13 healthy volunteers. The area under the concentration time curve from time zero to infinity and the maximum concentration of drug in serum for both drugs were reduced by Ensure in comparison with those by water (P < 0.01). However, Ensure reduced the percent relative bioavailability of ciprofloxacin (72% ± 14%; range, 52 to 96%) significantly more than ofloxacin (90% ± 8.3%; range, 74 to 105%) (P < 0.005). Coadministration of Ensure significantly diminished ciprofloxacin and ofloxacin absorption, but ciprofloxacin absorption was reduced significantly more than ofloxacin absorption.Fluoroquinolone antibiotics represent an important therapeutic advance in the treatment of bacterial infections. The beneficial characteristics of these agents include unique spectra of antimicrobial activity, favorable side effect profiles, and the advantages of both oral and parenteral routes of administration. Many serious infections which previously could be treated only with parenteral drugs can now be treated with an oral fluoroquinolone. The availability of oral fluoroquinolones has allowed more patients to be treated as outpatients and has expanded the use of oral antibiotics to the nursing home and critical care setting (49) to reduce drug costs (12,31,37).The oral bioavailabilities of fluoroquinolone antibiotics may be affected adversely by interactions with divalent cations (1,22,35,39,41). Divalent cations contribute to the clinically important interactions of fluoroquinolone antibiotics with food (9,15,16,18,19,27,42,43,45), vitamins with iron (4, 17, 36), antacids (8,14,21,28,40,41), and sucralfate (10,32,44). Of the two most studied fluoroquinolones, ciprofloxacin absorption appears to be affected more than ofloxacin absorption (6,15,26).The reduced bioavailabilities of oral fluoroquinolone antibiotics because of drug interactions may be important, particularly in the critical care setting, because therapeutic failures have been reported (30,38). The practice of using the enteral rather than the parenteral route to provide nutrition is becoming more common in intensive care units (ICUs) Because of the increasingly common practices of using oral fluoroquinolones and enteral feedings in ICU and nursing home settings, many patients may receive both of these therapies concurrently (23). We conducted a study to assess the influence that concomitant enteral feeding with an enteral feeding product (Ensure) has on the absorption of oral ciprofloxacin and ofloxacin.
MATERIALS AND METHODSProtocol. Thirteen healthy adults gave informed consent and were enrolled in the study. Subjects were excluded if they were pregnant or were intending to become pregnant within 30 days of the conclusion of the study. Other exclusion criteria included breastfeeding at the time of the study and use of any medications during the 24 h prior to the study periods. Any known allergies to t...