Multiple-dose pharmacokinetics and tolerability of gemifloxacin administered orally to healthy volunteers

Gemifloxacin mesylate (SB-265805-S, LB-20304a) is a potent, novel fluoroquinolone agent with a broad spectrum of antibacterial activity. The pharmacokinetics and tolerability of oral gemifloxacin were characterized in two parallel group studies in healthy male volunteers after doses of 160, 320, 480, and 640 mg once daily for 7 days. Multiple serum or plasma and urine samples were collected on days 1 and 7 and were analyzed for gemifloxacin by high-performance liquid chromatography (HPLC)-fluorescence (study 1) or HPLC-mass spectrometry (study 2). Safety assessments included vital signs, 12-lead electrocardiogram (ECG) readings, hematology, clinical chemistry, urinalysis, and adverse experience monitoring. Gemifloxacin was rapidly absorbed, with a time to maximum concentration of approximately 1 h after dosing followed by a biexponential decline in concentration. Generally, maximum concentration and area under the concentration-time curve (AUC) increased linearly with dose after either single or repeat doses. Mean +/- standard deviation values of AUC(0-tau) on day 7 were 4.92 +/- 1.08, 9.06 +/- 2.20, 12.2 +/- 3.69, and 20.1 +/- 3.67 microg x h/ml following 160-, 320-, 480-, and 640-mg doses, respectively. The terminal-phase half-life was approximately 7 to 8 h, independent of dose, and was similar following single and repeated administrations. There was minimal accumulation of gemifloxacin after multiple dosing. Approximately 20 to 30% of the administered dose was excreted unchanged in the urine. The renal clearance was 160 ml/min on average after single and multiple doses, which was slightly greater than the accepted glomerular filtration rate (approximately 120 ml/min). These data show that the pharmacokinetics of gemifloxacin are linear and independent of dose. Gemifloxacin was generally well tolerated, although one subject was withdrawn from the study after 6 days at 640 mg for mild, transient elevations of alanine aminotransferase and aspartate aminotransferase not associated with any clinical signs or symptoms. There were no other significant changes in clinical chemistry, hematology or urinalysis parameters, vital signs, or ECG readings. In conclusion, the results of these studies, combined with the antibacterial spectrum and potency, support the further investigation of once-daily administration of gemifloxacin for indications such as respiratory tract and urinary tract infections.

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Absorption, disposition, and metabolism of rosiglitazone, a potent thiazolidinedione insulin sensitizer, in humans

Rosiglitazone is a potent peroxisome proliferator-activated receptor gamma agonist that decreases hyperglycemia by reducing insulin resistance in patients with type 2 diabetes mellitus. The disposition of (14)C-labeled rosiglitazone was determined after oral and i.v. dosing of rosiglitazone solution, and the disposition of nonradiolabeled rosiglitazone was determined after oral dosing of tablets in this open-label, three-part, semirandomized, crossover study. The absorption of rosiglitazone was rapid and essentially complete, with absolute bioavailability estimated to be approximately 99% after oral tablet dosing and approximately 95% after oral solution dosing, and clearance was primarily metabolic. The time to maximal concentration of radioactivity and the elimination half-life for two metabolites in plasma were significantly longer than for rosiglitazone itself (4-6 h versus 0. 5-1 h, and ca. 5 days versus 3-7 h). Radioactivity was excreted primarily via the urine ( approximately 65%) and was excreted similarly after oral and i.v. dosing. The major routes of metabolism were N-demethylation and hydroxylation with subsequent conjugation, of which neither was affected by the route of drug administration. The major metabolites, those of intermediate importance, and nearly all of the trace metabolites in humans have been identified previously in preclinical studies. Rosiglitazone was well tolerated in all formulations.

Evaluation of phototoxic potential of gemifloxacin in healthy volunteers compared with ciprofloxacin

This double-blind, randomized, parallel-group comparative study investigated the phototoxic potential of gemifloxacin mesylate, a potent, novel fluoroquinolone antimicrobial. Forty healthy male and female volunteers received repeat dosing for 7 days with 160 mg or 320 mg of gemifloxacin (o.d., p.m.), 500 mg of ciprofloxacin (b.d.) or placebo (b.d.). On day 5 (large step) and day 6 (small step), graded series of wavebands were irradiated onto the back of each volunteer (phototesting). Skin reactions were assessed 0-30 min (immediate erythema) and 24 and 48 h (delayed erythema) after irradiation. Both gemifloxacin, 320 mg o.d., and ciprofloxacin, 500 mg b.d., were associated with mild phototoxicity following 7 days of administration. The range of mean phototoxic indices (the ratio of minimal erythemal dose at baseline compared with that on day 7 at the end of dosing) was 1.00-2.19 for gemifloxacin and 0.97-2.23 for ciprofloxacin. The abnormal responses occurred within the ultraviolet A region (335-365 +/-30 nm) and were maximal at 24 h. Susceptibility to phototoxicity had cleared 48 h after stopping the drug. The phototoxicity observed with gemifloxacin, 160 mg o.d., was lower than that at the higher dose and similar to that of placebo, suggesting that gemifloxacin phototoxicity is dose dependent. There were no clinically important changes in the safety profiles of gemifloxacin and ciprofloxacin compared with placebo in healthy volunteers after 7 days of repeat dosing. This study demonstrated that gemifloxacin, 320 mg o.d. given for 7 days, has a low potential to cause mild photosensitivity which is similar to that of ciprofloxacin, 500 mg b.d., given for the same period.

Lack of pharmacokinetic interaction between gemifloxacin and digoxin in healthy elderly volunteers

Gemifloxacin is a novel fluoroquinolone with a broad spectrum of antibacterial activity. The objective of this double-blind, randomized, placebo-controlled, 2-way crossover study was to demonstrate the lack of a pharmacokinetic interaction between gemifloxacin and digoxin. During two 14-day treatment periods, healthy elderly volunteers received digoxin (0.25 mg, once daily) co-administered on days 8-14 with either gemifloxacin (320 mg, p.o., once daily) or placebo. On day 14 of each period, blood samples and urine were collected for 24 h post dose and analysed for digoxin levels by radioimmunoassay. Steady-state digoxin pharmacokinetics were not affected by multiple dosing with gemifloxacin. There was no significant difference in digoxin values for the area under the plasma concentration-time curve over the dosing interval 0-24 h (AUC((0-24))) or the trough plasma concentration (C24) after co-administration with either gemifloxacin or placebo. Geometric means for AUC((0-24)) and C24 were 18.1 and 17.8 ng x h/ml and 0.597 and 0.566 ng/ml, respectively. The point estimates (90% confidence intervals) for AUC((0-24)) and C24 (digoxin + gemifloxacin):(digoxin + placebo) were 1.01 (0.93, 1.10) and 1.05 (0.95, 1.16), respectively, entirely within the equivalence range (0.80, 1.25). There were no marked differences between co-administration regimens for maximum observed plasma concentration (C(max)) or renal clearance values. Gemifloxacin was well tolerated during co-administration with digoxin, and the incidence of adverse events was similar to that seen with placebo. There were no clinically relevant changes in vital signs, electrocardiogram readings or laboratory parameters. In conclusion, this study demonstrates that gemifloxacin may be co-administered with digoxin without the need for digoxin dose adjustment.

Effect of omeprazole on the pharmacokinetics of oral gemifloxacin in healthy volunteers

This randomized, double-blind, 2-way crossover study investigated the effect of omeprazole on the pharmacokinetics of gemifloxacin, a novel fluoroquinolone. Thirteen healthy male volunteers received a 320 mg oral dose of gemifloxacin after 4 days of dosing with either omeprazole (40 mg once daily) or matching placebo. Blood was sampled for 48 h after dosing for determination of pharmacokinetic parameters. The mean area under the plasma concentration-time curve extrapolated to infinity (AUC(0-infinity)) and maximum plasma concentration (C(max)) for gemifloxacin were increased by, on average, 10% (90% confidence interval [CI], 0.89, 1.36) and 11% (90% CI, 0.87, 1.43), respectively, when gemifloxacin was given after omeprazole compared with after placebo. Neither the time to C(max) (T(max)) nor the half-life of gemifloxacin appeared to be affected by administration of omeprazole. There were no clinically relevant changes in adverse events, vital signs or the results of laboratory investigations after co-administration of omeprazole compared with placebo. In view of the modest increase in systemic exposure and the likely maximal increases indicated by the CIs, the effect of omeprazole on gemifloxacin pharmacokinetics is not considered to be clinically significant. Gemifloxacin and omeprazole can therefore be co-administered with no requirement for a dose adjustment.

Effect of Maalox on the bioavailability of oral gemifloxacin in healthy volunteers

This open, randomized, 4-way crossover study investigated the effect of the antacid Maalox on the bioavailability of gemifloxacin, a novel fluoroquinolone antimicrobial. Sixteen healthy male volunteers received gemifloxacin, 320 mg p.o., alone, 3 h after Maalox administration, or 10 min or 2 h before Maalox administration. Blood was sampled for 48 h after dosing to determine pharmacokinetic parameters. Estimates for the differences between regimens and 95% confidence intervals were calculated using the t-test for paired data. The administration of gemifloxacin 10 min before Maalox resulted in an average 85% reduction in the area under the plasma concentration-time curve from time zero extrapolated to infinity (AUC(0-infinity)), whereas administration 3 h after Maalox produced a decrease in AUC(0-infinity), 15% of which was not considered to be clinically significant. The administration of gemifloxacin 2 h before Maalox had no notable effect on the gemifloxacin AUC(0-infinity) (average increase of 3%). Similar results were seen for the maximum gemifloxacin plasma concentration (C(max)). Neither the time to C(max) nor the half-life of gemifloxacin were notably altered by the administration of Maalox at any time relative to gemifloxacin dosing. There were no clinically important adverse experiences or changes in clinical laboratory parameters during this study. The findings of this study support the dosing recommendation that gemifloxacin can be administered either 2 h or more prior to, or 3 h or more after, the administration of Maalox.