The activities of levofloxacin and ofloxacin against 22 clinical legionella isolates was determined by microbroth dilution susceptibility testing. Growth inhibition of two Legionella pneumophila strains grown in guinea pig alveolar macrophages by levofloxacin, ofloxacin, or erythromycin was also determined. The drug concentrations required to inhibit 90% of strains tested was 0.032 mg/L for levofloxacin or ofloxacin, and was 0.016 mg/L for ciprofloxacin. BYE alpha broth significantly inhibited the activities of all three drugs tested, as judged by the susceptibility of control Escherichia coli strains. Levofloxacin (0.25 mg/L) reduced bacterial counts of two L. pneumophila strains grown in guinea pig alveolar macrophages by 1 log10, but regrowth occurred over a 3 day period; levofloxacin (1 mg/L) reduced bacterial counts by 2-3 log10 cfu/mL. Levofloxacin was significantly more active than erythromycin, and as active as ofloxacin or ciprofloxacin in this assay. Pharmacokinetic and therapy studies of levofloxacin and ofloxacin were performed in guinea pigs with L. pneumophila pneumonia. For the pharmacokinetic study, levofloxacin was given (10 mg/kg) by the intraperitoneal route to infected guinea pigs; mean peak plasma and lung concentrations were 3.4 mg/L and 1.4 micrograms/g, respectively, at 0.5 h and 2.6 mg/L and 0.6 micrograms/g at 1 h. The terminal half-life phase of elimination from plasma and lung was c. 1 h. All 15 infected guinea pigs treated with levofloxacin (10 mg/kg/day given ip once daily) for 5 days survived for 9 days after antimicrobial therapy, as did all 14 guinea pigs treated with the same dose of ofloxacin. None of 13 animals treated with saline survived. Levofloxacin is effective against L. pneumophila in vitro and in a guinea pig model of legionnaire's disease. Levofloxacin should be evaluated as a treatment of human legionnaires' disease.
Twelve healthy fasting male volunteers received glimepiride in 1, 2, 4 or 8 mg single oral doses. On the days when glimepiride was taken, the subjects were given a standardised carbohydrate diet (18 bread exchange units) and drank 125 ml of water hourly. Blood and urine samples were taken before drug administration and afterwards for up to 36 hours (blood) and 48 hours (urine) to determine serum and urinary concentrations of glimepiride and its hydroxy- and carboxy-metabolites (M1 and M2). The areas under the curve for glimepiride after oral doses of 1 to 8 mg and the urinary recovery of its metabolites M1 and M2 were dose linear. All confidence intervals were well contained within the bioequivalence range of 80-125%. There was a statistically significant difference for Cmax values of glimepiride between doses after dose normalisation. A dose-dependent increase for Cmax was nevertheless clearly observed with a correlation coefficient of r=0.90. The pharmacokinetics of glimepiride are dose linear in the dose range 1 to 8 mg, and glimepiride was safe and well tolerated in healthy volunteers.
Twelve healthy fasting male volunteers received a single 1.0 mg dose of glimepiride either as an intravenous injection over one minute or as a tablet. Blood and urine samples were taken before drug administration and afterwards for up to 24 hours (blood) and 48 hours (urine) to determine serum and urinary concentrations of glimepiride and its hydroxy- and carboxy-metabolites (M1 and M2). There were no statistically significant differences between mean serum pharmacokinetic parameters for the oral and intravenous formulations either with glimepiride or M1. Mean urinary recovery of M1 plus M2 was 50% of the dose for the glimepiride tablet and 51% for the intravenous injection. The absolute bioavailability of the tablet formulation was 107% (AUDC(glimepiride)), 109% (AUDC(M1)) and 97% (urinary recovery). The tablet formulation of glimepiride is completely bioavailable and was safe and well tolerated in healthy volunteers.
HMR1766 is a new nitric oxide (NO)-independent activator of soluble guanylyl cyclase (sGC) in development for the treatment of cardiovascular diseases and chronic heart failure. A significant fraction of patients to be treated with HMR1766 is expected to be maintained on warfarin. Because HMR1766 is an inhibitor and warfarin a substrate of CYP2C9, the authors studied whether warfarin pharmacokinetics and pharmacodynamics are influenced by HMR1766. Eighteen healthy males were to receive a single oral dose of 20 mg warfarin each under steady-state conditions of HMR1766 or placebo. Plasma concentrations of HMR1766, (R)- and (S)-warfarin, and its 7-hydroxy-metabolites were determined using high-performance liquid chromatography and prothrombin time, and the international standardized ratio was determined by the nephelometric method. (S)-Warfarin AUC(inf) and t(1/2) were 106,471 h x microg/L and 82.92 hours versus 33,148 h x microg/L under HMR1766 and 31.72 hours under placebo, and the maximum decrease in prothrombin time values after warfarin dosing was 58.75% versus 39.94%. These data demonstrate a CYP2C9-mediated pharmacokinetic interaction with pharmacodynamic, clinically relevant consequences, which might require warfarin dose adjustment.
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