Effect of Ensure on the Oral Bioavailability of Gatifloxacin in Healthy Volunteers

Study Objective . To determine the effect of Ensure on the relative oral bioavailability of gatifloxacin in healthy volunteers. Design . Single‐dose, randomized, crossover study. Setting . University‐affiliated research center. Subjects . Twelve healthy volunteers (six men, six women) aged 18 years or older with no clinically significant abnormal findings on physical examination or in medical history. Intervention . Subjects consumed 120 ml of study liquid—water or Ensure—every 30 minutes for five doses. With the second dose, subjects ingested a single gatifloxacin 400‐mg tablet that had been uniformly crushed and mixed into the study liquid. Measurements and Main Results . Serial blood samples were collected for 48 hours, and gatifloxacin concentrations were determined by high‐performance liquid chromatography. Pharmacokinetic data were analyzed by using noncompartmental methods. Maximum serum concentration (C max ) and area under the serum concentration‐time curve from zero to infinity (AUC 0–∞ ) were tested for bioequivalence after log‐transformation of the data. Comparison of parameters for gatifloxacin administered with water versus those with Ensure showed that C max (4.35 ± 0.90 vs 2.41 ± 0.58 μg/ml, p<0.0001) and AUC 0–∞ (42.4 ± 10.1 vs 31.3 ± 8.3 mg•hr/L, p<0.0001) were significantly decreased with Ensure, and bioequivalence was not achieved for either parameter. The geometric least squares mean ratio was 0.553 (90% confidence interval [CI] 0.501–0.611) for C max and 0.730 (90% CI 0.664–0.802) for AUC 0–∞ . The median time to reach C max was significantly prolonged when gatifloxacin was administered with Ensure versus that with water (2.5 hrs vs 1.0 hr, p=0.006). Conclusions . The C max and AUC 0–∞ of gatifloxacin were significantly decreased when the drug was administered with Ensure. The clinical significance of these findings will depend on the offending pathogen and its susceptibility to gatifloxacin.