The purpose of this study was to assess the pharmacokinetic profile of ciprofloxacin in 12 patients with diabetic gastroparesis. Patients received both a single 500-mg oral (p.o.) dose and a single 400-mg intravenous (i.v.) dose of ciprofloxacin separated by a 1-week washout period. Pharmacokinetic parameters (means +/- standard deviations) for the p.o. and i.v. doses were as follows: areas under the concentration-time curve from 0 h to infinity, 9.74 +/- 2.59 and 11.78 +/- 3.18 micrograms.h/ml, respectively; maximum concentrations of drug in serum, 2.13 +/- 0.67 and 4.21 +/- 1.07 micrograms/ml, respectively; and half-lives, 4.03 +/- 0.58 and 4.20 +/- 0.58 h, respectively. The ratio of the areas under the concentration-time curves from 0 h to infinity for the p.o. and i.v. doses was 0.84, with a 90% confidence interval of 0.68 to 0.98; the mean absolute bioavailability was calculated to be 67% (range, 43 to 82%). From these data it appears that ciprofloxacin is adequately absorbed in patients with diabetic gastroparesis.