The pharmacokinetics and bioavailabiity of ofloxacin in 20 healthy male volunteers were studied in an open-label, randomized, two-way crossover study. Ofloxacin (400 mg) was administered either as a 1-h infusion or as an oral tablet. The mean peak concentration after intravenous infusion was 4.30 0.69 ,ug/ml, and that after oral administration was 3.14 ± 0.53 ,ug/mI, occurring 1.74 + 0.57 h after dosing. The bioavailability (F) of the oral dosage form of ofloxacin was virtuaUy identical to that of the intravenous form (F = 105% 7%). This complete bioavailability of ofloxacin is supportive of the use of the oral dosage form for the treatment of infections in hospitalized patients either as a replacement for intravenous ofloxacin therapy or in streamlining therapy from the intravenous to the oral route.Ofloxacin is a synthetic, fluorinated carboxyquinolone active against members of the family Enterobactericeae and gram-positive organisms. Its favorable pharmacokinetic features include good oral absorption and lack of metabolism resulting in decreased drug interaction. The presence of the methyl piperazine ring in ofloxacin probably leads to enhanced oral absorption and a long half-life (properties shown by other quinolones such as pefloxacin, fleroxacin, and difloxacin). Pharmacokinetic disposition and bioavailability have been previously studied in different study populations, and the bioavailability of ofloxacin has been reported to be 80 to 90% (1, 2, 4, 5, 7). There is a paucity of data, however, directly comparing oral (p.o.) and intravenous (i.v.) dosage forms in the same population. The present study was undertaken to evaluate the bioavailabilities of orally and parenterally administered ofloxacin in normal volunteers. An accurate determination of bioavailability is necessary for considering the use of oral ofloxacin in place of the parenteral form in the treatment of hospitalized patients.On the basis of laboratory tests (serum chemistry, hematology, urinalysis), medical history, and physical examination, 20 healthy male volunteers (age, 25 ± 4.6 years; weight, 74.5 ± 7.87 kg; height, 178.3 ± 5.92 cm [mean ± standard deviation]) were enrolled in this study after giving written informed consent. No alcohol or concomitant medication was allowed 72 h prior to the initial administration of the dose and for the entire duration of the study. All subjects reported to the study site at least 12 h prior to the administration of the initial dose, remained within the facility for 36 h after each dose, and returned to the study site for the 48-h scheduled blood draw. Subjects were dosed in the mornings of day 1 and day 8. Subjects fasted at least 8 h prior to each dose and remained fasted for 2 h postdose. Water was permitted ad lib until 2 h prior to and 2 h after dosing. Tablets containing 400 mg of ofloxacin (FD 18489-BS-22) and 10-ml single-dose vials containing 400 mg of ofloxacin (FD 18489-* Corresponding author. BR-45) for parenteral use were provided by Ortho Pharmaceutical Corporation.The tablets were admin...