Effect of Maalox and omeprazole on the bioavailability of trovafloxacin

To determine the effect of the concurrent administration of Maalox and omeprazole in the bioavailability of trovafloxacin (CP-99,219), an open, placebo-controlled, randomized, four-way crossover study was conducted in 12 healthy male volunteers. Each received treatments of three 100 mg trovafloxacin tablets in the morning 30 min after 30 mL of Maalox (A), 30 min after placebo (B), 2 h before 30 mL of Maalox (C) and 2 h after 40 mg of omeprazole (D). For treatments A and C, Maalox was also given at 22.00 h the night before the study day, 1 and 3 h after meals and at bedtime on the study day. For B and D, placebo and omeprazole, respectively, were also given at 22.00 h the night before the study day. After treatments A and C, mean area under the curve (AUC) was reduced by 66% and 28% (14.2 and 30.2 mg.h/L), respectively, and mean T(1/2) declined by 33% and 31% (8.3 and 8.5 h), respectively, relative to the values after B (42.1 mg.h/L; 12.4 h). The mean Kel-corrected relative bioavailabilities for A and C were 50% and 104%, respectively, suggesting a large reduction in the initial absorption of trovafloxacin with A. Treatment D had no appreciable effect on mean T(1/2) but mean AUC and Cmax were reduced by 18% and 32%, respectively, relative to B. The mean relative bioavailability after D was 82%. We conclude that the concurrent administration of trovafloxacin and aluminium- and magnesium-containing antacids should be avoided but that co-administration with omeprazole is unlikely to have a clinically significant effect on the extent of absorption of the antibiotic.