EFFECT OF MULTIPLE STAGGERED DOSES OF CALCIUM ON THE BIOAVAILABILITY OF CIPROFLOXACIN

OBJECTIVE: To determine the effect on the relative bioavailability (Fr ) of a staggered single dose of ciprofloxacin given two hours a mornin g dose of calcium carbonate given three times daily over the three pre vious days. DESIGN: Thirteen male volunteers participated in this rand omized, nonblinded, crossover investigation; 12 subjects were included in the final analysis. SETTING: Data collection and ciprofloxacin adm inistration occurred at Albany Medical Center, a tertiary-care teachin g institution. Calcium carbonate administration was on an outpatient b asis. RESULTs: For 12 volunteers, the mean +/- SD Fr of ciprofloxacin staggered with calcium was 0.87 +/- 0.23 (noncompartmental model) and 0.98 +/- 0.27 (compartmental model). Other statistically significant f indings were a decrease in the time to maximum concentration of ciprof loxacin staggered with calcium in serum compared with ciprofloxacin al one (from 1.76 +/- 0.54 to 1.23 +/- 0.52 h in the noncompartmental mod el; p<0.05), and a decrease in the same parameter (from 1.92 +/- 0.96 to 0.77 +/- 0.53 in the compartmental model; p<0.005). Maximum concent ration of ciprofloxacin staggered with calcium was decreased in the no ncompartmental model compared with ciprofloxacin alone (from 2.11 +/- 0.72 to 1.60 +/- 0.33, respectively; p<0.05). The elimination half-lif e and area under the concentration-time curve of ciprofloxacin were no t significantly altered.CONCLUSIONS: Repeated doses of calcium carbona te, administered two hours before ciprofloxacin, did not significantly alter the Fr of this fluoroquinolone.