Pharmacodynamics to combat resistance

The ability to identify agents with the optimal combination of potency, pharmacokinetics and pharmacodynamics should help to maximize bacteriological cure and thus minimize the potential for selection and spread of resistance. Gemifloxacin demonstrated excellent correlation between efficacy and the AUC0-24h/MIC ratio whereas there was little correlation with time above MIC. Thus, gemifloxacin is similar to other quinolones in that it is the amount of drug present, not the frequency of administration, that determines antibacterial effect. In a neutropenic murine thigh model of infection, caused by Gram-negative bacilli, a AUC0-24h/MIC ratio of approximately 100 was necessary to protect >90% of the animals, which is similar to data reported previously for other quinolones. However, in order to achieve the same protection in an immunocompetent murine infection caused by Streptococcus pneumoniae, the AUC-24h/MIC ratio was approximately 25. The magnitude of this AUC0-24h/MIC ratio did not alter for strains exhibiting penicillin or macrolide resistance. Importantly, when gemifloxacin was examined against strains of S. pneumoniae with well-characterized ciprofloxacin resistance (including mutations in gyrase, parC and parE as well as efflux strains) there was little impact on the in vivo efficacy. Overall, the data showed a trend towards a decrease in the AUC0-24h/MIC ratio for these more resistant strains. The lower AUC0-24h/MIC ratio was especially noticeable for the efflux mutants suggesting that the quinolone efflux mechanism may be down-regulated in vivo and may be of minimal relevance to the clinical activity of gemifloxacin against S. pneumoniae. The efficacy of gemifloxacin, in comparison with other oral agents used to treat respiratory infections, has also been evaluated in a rat model using doses, and therefore AUC0-24h/MIC ratios, that approximate those in man. These data confirm the excellent activity of gemifloxacin against strains of Haemophilus influenzae and S. pneumoniae, including those demonstrating penicillin, macrolide and quinolone resistance.

Pharmacokinetics and tolerability of gemifloxacin (SB-265805) after administration of single oral doses to healthy volunteers

Gemifloxacin (known as SB-265805 or LB-20304) is a potent, novel fluoroquinolone compound with a broad spectrum of antibacterial activity. The pharmacokinetics and tolerability of oral gemifloxacin were characterized in healthy male volunteers after a single dose of 20, 40, 80, 160, 320, 600, or 800 mg. Multiple serum and urine samples were collected and analyzed for gemifloxacin using high-performance liquid chromatography with fluorescence detection. Safety assessments included vital signs, 12-lead electrocardiogram readings, hematology, clinical chemistry, urinalysis, and adverse-experience monitoring. Gemifloxacin was rapidly absorbed after all doses. Maximum concentrations of gemifloxacin in serum (C(max)) were achieved approximately 1 h after dosing, after which concentrations in serum declined in a biexponential manner. Values of C(max) and the area under the concentration-time curve in serum from 0 h to infinity (serum AUC(0-infinity)) increased linearly with dose. Serum AUC(0-infinity) values (mean +/- standard deviation) were 0.65+/-0.01, 1.28+/-0.22, 2.54+/-0.31, 5.48+/-1.24, 9.82+/-2.70, 24.4+/-7.1, and 31.4+/-7.6 microg. h/ml following 20-, 40-, 80-, 160-, 320-, 600-, and 800-mg doses, respectively. The terminal phase elimination half-life was independent of dose, with an overall mean of 7.4+/-2.0 h. The profiles indicated that the pharmacokinetic profile is suitable for a once-daily dosing regimen. Approximately 25 to 40% of the administered dose was excreted unchanged in the urine, and renal clearance (ca. 150 ml/min) was independent of dose. There were no significant changes in clinical chemistry, hematology, or urinalysis parameters, vital signs, or 12-lead electrocardiogram readings in subjects, irrespective of dose. The results of these studies support the further investigation of once-daily administration of gemifloxacin.

Activities of trovafloxacin and ampicillin-sulbactam alone or in combination versus three strains of vancomycin- intermediate Staphylococcus aureus in an in vitro pharmacodynamic infection model

The recent isolation of clinical strains of methicillin-resistant Staphylococcus aureus (MRSA) with intermediate susceptibility (MICs, 8 microg/ml) to vancomycin (vancomycin-intermediate S. aureus [VISA]) emphasizes the importance of developing novel antimicrobial regimens and/or agents for future treatment. We studied the activities of ampicillin-sulbactam and trovafloxacin alone or in combination against three unique strains of VISA in an in vitro infection model. Two VISA strains were trovafloxacin susceptible (MICs, < or =2 microg/ml); one VISA strain was trovafloxacin resistant (MIC, 4 microg/ml). Trovafloxacin was administered to simulate a dose of 200 or 400 mg every 24 h. Ampicillin-sulbactam was administered to simulate a dose of 3 g every 6 h. Samples were removed from the infection models over 48 h, and reductions in colony counts were compared between regimens. Trovafloxacin (200 mg) produced rapid killing of a control MRSA strain over the 48-h experiment but produced only slight killing of all three VISA strains. The higher dose of trovafloxacin improved killing but did not produce bactericidal activity at 48 h. Ampicillin-sulbactam produced rapid bactericidal activity against all four strains tested, and colony counts at 8 h were at the limits of detection. However, regrowth occurred by 48 h for each strain. The combination of ampicillin-sulbactam and trovafloxacin provided additive activity against two of the three VISA strains. In conclusion, trovafloxacin or ampicillin-sulbactam alone did not provide adequate activity against the VISA strains for the 48-h evaluation period, but the combination could help improve activity against some strains of VISA.

Pharmacokinetics of a fluoronaphthyridone, trovafloxacin (CP 99,219), in infants and children following administration of a single intravenous dose of alatrofloxacin

The pharmacokinetics of trovafloxacin following administration of a single intravenous dose of alatrofloxacin, equivalent to 4 mg of trovafloxacin per kg of body weight, were determined in 6 infants (ages 3 to 12 months) and 14 children (ages, 2 to 12 years). There was rapid conversion of alatrofloxacin to trovafloxacin, with an average +/- standard deviation (SD) peak trovafloxacin concentration determined at the end of the infusion of 4.3 +/- 1.4 microg/ml. The primary pharmacokinetic parameters (average +/- SD) analyzed were volume of distribution at steady state (1.6 +/- 0.6 liters/kg), clearance (151 +/- 82 ml/h/kg), and half-life (9.8 +/- 2.9 h). The drug was well tolerated by all children. There were no age-related differences in any of the pharmacokinetic parameters studied. Less than 5% of the administered dose was excreted in the urine over 24 h. On the basis of the mean area under the concentration-time curve of 30.5 +/- 10.1 microg. h/ml and the susceptibility (< or =0.5 microg/ml) of common pediatric bacterial pathogens to trovafloxacin, dosing of 4 mg/kg/day once or twice daily should be appropriate.

Gemifloxacin

Gemifloxacin is a fluoroquinolone antibacterial agent which has an enhanced affinity for topoisomerase i.v.. It has potent activity against most Gram-positive bacteria, particularly Streptococcus pneumoniae. Gemifloxacin is over 30-fold more active than ciprofloxacin and 4- to 8-fold more active than moxifloxacin against this pathogen. Gemifloxacin has excellent activity against Haemophilus influenzae and Moraxella catarrhalis, and is unaffected by beta-lactamase production. It is generally 2-fold less active than ciprofloxacin against most Enterobacteriaceae. Atypical respiratory pathogens (Legionella, Mycoplasma and Chlamydia spp.) are highly susceptible to gemifloxacin. Preliminary results from phase II trials show that oral gemifloxacin 320 mg/day produced bacteriological responses of 94.7% in patients with acute exacerbations of chronic bronchitis and 95% of patients with uncomplicated urinary tract infections. Adverse events included nausea, abdominal pain, headache and mild rash in patients and healthy volunteers treated with gemifloxacin 320 mg/day. Gemifloxacin has a low potential for mild phototoxicity (comparable to that of ciprofloxacin).

Pharmacokinetics of intravenous trovafloxacin in critically ill adults

The pharmacokinetic disposition of numerous antimicrobial agents is altered in critically ill patients. Pharmacokinetics of trovafloxacin, a fluoroquinolone indicated specifically for severe, life-threatening infections in the intensive care unit, have not been well studied in this population. We characterized the pharmacokinetic disposition of trovafloxacin after administration of alatrofloxacin, the intravenous prodrug, in critically ill adults. Seven patients (3 men, 4 women; mean +/- SD age 59.4 +/- 20.6 yrs; baseline aspartate aminotransferase [AST]/alanine aminotransferase [ALT] 66.0 +/- 40.6/51.5 +/-37.5 IU/L; median Acute Physiology and Chronic Health Evaluation [APACHE II] score 27, range 15-32) were studied at estimated steady state. Calculated (mean +/- SD) half-life, clearance at steady state, and volume of distribution in all patients were 10.9 +/- 1.8 hours, 161.3 +/- 41.1 ml/minute, and 1.4 +/- 0.4 L/kg. In patients receiving 300 mg, maximum concentration, minimum concentration, and area under the curve from 0-24 hours were 3.6 +/- 0.5 mg/L, 0.6 +/- 0.3 mg/L, and 34.2 +/- 10.6 mg x hr/L, respectively. These results are consistent with published values in other patient populations, indicating that trovafloxacin pharmacokinetics are not substantially altered in critically ill patients with normal or mildly impaired hepatic function.

A comparison of the photosensitizing potential of trovafloxacin with that of other quinolones in healthy subjects

Treatment with some quinolones is associated with an abnormal skin reaction following exposure to sunlight (photosensitivity). The objective of the current study was to compare the photosensitizing potential of a new quinolone, trovafloxacin, with that of ciprofloxacin, lomefloxacin and placebo. Forty-eight healthy males (age range 19-45 years) were randomized to receive a 7 day course of treatment with: (i) trovafloxacin 200 mg od; (ii) ciprofloxacin 500 mg bd; (iii) lomefloxacin 400 mg od; or (iv) placebo bd. Minimal erythema doses (MEDs) were assessed using a monochromator at baseline and on day 5 of treatment, for wavelengths of 305 +/- 5, 335 +/- 30, 365 +/- 30, 400 +/- 30 and 430 +/- 30 nm; 335 +/- 30 and 365 +/- 30 nm are within the UVA range. Immediate reaction MEDs were similar in all treatment groups. However, between baseline and day 5, the mean decreases in delayed-reaction MED (24 h) at 335 +/- 30 nm were only 18.99% for trovafloxacin versus placebo (P = 0.1267), compared with 53.77% (P 0.0001) and 64.13% (P 0.0001) for ciprofloxacin and lomefloxacin, respectively. Similarly, at 365 +/- 30 nm, trovafloxacin produced the smallest reduction in delayed MED versus placebo (43.66%), compared with ciprofloxacin (61.53%) and lomefloxacin (75.81%). These differences between trovafloxacin and ciprofloxacin and lomefloxacin were significant at both 335 +/- 30 and 365 +/- 30 nm (P 0.029). All MED values returned to baseline levels within 2 days of drug cessation. These results show that trovafloxacin has significantly less photosensitizing potential than either ciprofloxacin or lomefloxacin. This photosensitivity appears to be induced only by wavelengths in the UVA region, is maximal at 24 h and is a short-term effect.

Gemifloxacin is effective in experimental pneumococcal meningitis

In a rabbit model of Streptococcus pneumoniae meningitis, 5 mg of gemifloxacin mesylate (SB-265805) per kg/h reduced the bacterial titers in cerebrospinal fluid (CSF) almost as rapidly as 10 mg of ceftriaxone per kg/h (Deltalog CFU/ml/h +/- standard deviation [SD], -0.25 +/- 0.09 versus -0.38 +/- 0.11; serum and CSF concentrations of gemifloxacin were 2.1 +/- 1.4 mg/liter and 0.59 +/- 0.38 mg/liter, respectively, at 24 h). Coadministration of 1 mg of dexamethasone per kg did not affect gemifloxacin serum and CSF levels (2.7 +/- 1.4 mg/liter and 0.75 +/- 0.34 mg/liter, respectively, at 24 h) or activity (Deltalog CFU/ml/h +/- SD, -0.26 +/- 0.11).

Activities of trovafloxacin, gatifloxacin, clinafloxacin, sparfloxacin, levofloxacin, and ciprofloxacin against penicillin-resistant Streptococcus pneumoniae in an in vitro infection model

We adapted an in vitro pharmacodynamic model of infection to incorporate infected fibrin clots. The bactericidal activities of various fluoroquinolones against two strains of penicillin-resistant Streptococcus pneumoniae were studied over a 48-h period. Bacteria were prepared in Muller-Hinton broth by using colonies from a 24-h tryptic soy agar plus 5% sheep blood plate and were added to a mixture of cryoprecipitate (80%) and thrombin (10%) to achieve approximately 10(6) CFU of organism per fibrin clot. The fibrin clots were suspended into the models and removed, in triplicate, at various time points over 48 h. Control models were also conducted to characterize the growth of S. pneumoniae in the growth medium without antibiotic. Trovafloxacin, gatifloxacin, clinafloxacin, sparfloxacin, levofloxacin, and ciprofloxacin were administered to simulate their pharmacokinetic profiles in humans. Fibrin clot samples were also plated onto antibiotic-containing tryptic soy agar plus 5% lysed horse blood to detect resistance. The newer fluoroquinolones demonstrated better activity than ciprofloxacin against both isolates. In conclusion, the newer quinolones demonstrated significant activity against penicillin-resistant S. pneumoniae, with standard dosing resulting in area under the concentration-time curve/MIC ratios and peak concentration/MIC ratios that resulted in 99.9% killing against these isolates.

Trovafloxacin concentrations in airway fluids of patients with severe community-acquired pneumonia

The penetration of trovafloxacin (TVA), 200 mg once daily, into the airways of 17 patients with severe pneumonia was studied. The mean (standard deviations are given in parentheses) steady-state TVA concentrations, 2 h after the last intake, were 3.1 (0.3) mg/liter in induced sputum (n = 8), 3.2 (1.1) mg/liter in bronchial secretions (n = 9), 3.2 (0.9) mg/liter in bronchoalveolar lavage fluid (n = 10), and 4.9 (1.4) mg/liter in epithelial lining fluid (n = 11).

Evaluation of trovafloxacin in the treatment of Klebsiella pneumoniae lung infection in tumour-bearing mice

Trovafloxacin, a new trifluoroquinolone, was evaluated for its therapeutic efficacy against Klebsiella pneumoniae lung infection in tumour (P388 murine leukaemia cells)-bearing mice, treated with or without a chemotherapeutic agent, daunorubicin (DNR) and in mice without tumour. Its activity was compared with ciprofloxacin and cephazolin. The effect on therapeutic efficacy of the addition of recombinant granulocyte colony stimulating factor (rGCSF) was also examined. Our study showed that both quinolones successfully cured pneumonia owing to infection with K. pneumoniae in mice without tumours but that all antibiotics failed in tumour-bearing mice if DNR was withheld. Substantial differences were noted in DNR-treated tumour-bearing mice with infection-the cure rate with trovafloxacin was 91% whereas the cure rate with ciprofloxacin or cephazolin was 57%. Addition of rGCSF to ciprofloxacin did not substantially improve its efficacy (when assessed by protection against death owing to infection; the survival rate was 41%). Trovafloxacin cure rates ranged from 80 to 90% whether or not rGCSF was added to the treatment regimen. Our results suggest that prior cancer chemotherapy had no adverse effect on the therapeutic efficacy of trovafloxacin, and that trovafloxacin may be a promising therapeutic agent for treatment of bacterial infections in the presence of leucopenia.

Oral bioavailability and pharmacokinetics of trovafloxacin in patients with AIDS

Trovafloxacin pharmacokinetics were evaluated in 12 subjects with AIDS. By using a randomized design, single 200-mg doses of oral trovafloxacin and intravenous alatrofloxacin were administered. The mean absolute bioavailability was 91%. The pharmacokinetics of trovafloxacin when administered orally as the active form or intravenously as the prodrug (alatrofloxacin) are not altered in subjects with AIDS compared to those in healthy adults.

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.

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.

Gastrointestinal first-pass effect of YJA-20379-8, a new reversible proton pump inhibitor, in rats

Since low bioavailability of YJA-20379-8 (3-butyryl-4-[5-R-(+)-methylbenzylamino]-8ethoxy-1,7-naph thy ridine), a new reversible proton pump inhibitor, has been reported after oral administration of the drug to rats, the first-pass organ of the drug was investigated in rats. YJA-20379-8, 50 mg kg(-1), was infused over 1 min via the jugular vein (n=5) or the portal vein (n=5), or was instilled directly into the stomach (n=5) or the duodenum (n=5). After intravenous or intraportal infusion of the drug, the total body clearance of YJA-20379-8 (18.1 and 19.7 mL min(-1) kg(- 1) based on plasma data) was considerably lower than the reported cardiac output (296 mL min(-1) kg(-1) based on blood data) in rats. This data indicated that the first-pass effect of YJA-20379-8 by the lung and heart was negligible. The areas under the plasma concentration-time curve from time zero to time infinity (AUC) after intravenous or intraportal administration of YJA-20379-8 (2760 and 2540 microg min mL(-1)) were not significantly different, indicating that the hepatic first-pass effect of the drug was also negligible in rats. After intragastric or intraduodenal instillation of YJA-20379-8, the extent of absolute oral bioavailability was 18.2 and 33.8%, respectively. Based on gastrointestinal recovery studies, approximately 86.5 and 91.2% of YJA-20379-8 was absorbed from rat gastrointestinal tract after intragastric or intraduodenal instillation, respectively. The data indicated that gastrointestinal and intestinal first-pass effects of YJA-20379-8 were approximately 68% (86.5-18.2) and 57% (91.2-33.8), respectively. The AUC(0-24h) values of YJA-20379-8 were significantly different between intragastric and intraduodenal instillation, indicating that the gastric first-pass effect of the drug was approximately 10% in rats. Therefore, it could be concluded that the low F value of YJA-20379-8 after oral administration of the drug could be due to a considerable (approx. 60%) intestinal first-pass effect in rats.

Gastrointestinal absorption of a new reversible proton pump inhibitor, YJA-20379-8, and its pharmacokinetics after oral administration in acetic acid-induced gastric ulcer in rats

The absorption of YJA-20379-8 (3-butyryl-4-[5-(R)-(+)-methylbenzylamino]-8-ethoxy-1,7-naphthyrid ine) from various rat gastrointestinal segments was evaluated using in-situ closed-loops. The pharmacokinetics of the drug were also evaluated after oral administration to rats with acetic acid-induced gastric ulcer (AIURs). The concentrations of YJA-20379-8 in the biological samples were analyzed by HPLC. The absorption of YJA-20379-8 from stomach and jejunum was fast, but approximately 50% of the drug was recovered from each segment at 24 h. The total areas under the plasma concentration-time curves from time zero to 24h (AUC(0-24h)) were 161, 392, 233, 365, and 226 microg min mL(-1) for stomach, duodenum, jejunum, ileum, and colon, respectively. After oral administration of the drug, the plasma concentrations and the resultant AUC (0- 12h) were not significantly different between control and AIURs. The detection limits of YJA-20379-8 in human plasma and urine were 50 and 100 ng mL(-1), respectively. The results suggest that modification of the oral dose of YJA-20379-8 may not be required in gastric ulcer patients if the present rat pharmacokinetic data could be extrapolated to man.

[Pharmacokinetics of trovafloxacin: its clinical significance]

Trovafloxacin, once administrated by oral route, is rapidly absorbed and reaches its maximum seric concentration in about one hour. Alatrofloxacin is the prodrug, that is rapidly hydrolyzed to its original state when administered intravenously. Its bioavailability is equivalent when administered either oral or intravenously. It is a fluoroquinolone of extensive in vitro spectrum, with a higher activity for Gram positive coccus, anaerobic and atypical pneumonia-producing bacteria. The average half-life is around eleven hours, with an enhanced protein bound that allows to administrate it only once a day. The renal excretion is under 8%; it doesn't require any doses adjustment in renal insufficiency. Trovafloxacin reaches higher tissue and intracelular concentrations than classic fluoroquinolones. All these pharmacokinetic and pharmacodynamic characteristics allow to consider trovafloxacin as an interesting drug for the treatment of mixed infections or those resistant to the first line drugs.

The antibacterial efficacy of trovafloxacin against an experimental infection with Listeria monocytogenes in hydrocortisone-treated mice

The efficacy of trovafloxacin in treating Listeria monocytogenes infections in glucocorticosteroid-treated mice was compared with the efficacy of amoxycillin. Swiss mice were treated with daily injections of 2.5 mg hydrocortisone s.c. and then infected i.v. with 1 x 10(7) cfu of L. monocytogenes. Untreated, this level of infection resulted in 100% mortality between day 3 and day 5 after infection. Both s.c. trovafloxacin and amoxycillin were effective in reducing the number of viable L. monocytogenes in the liver and spleen. Although the MIC of amoxycillin for this isolate of L. monocytogenes was lower than that of trovafloxacin (0.063 mg/L versus 0.5 mg/L, respectively), trovafloxacin was more efficacious in vivo after a single dose in the dose range between 12.5 and 100 mg/kg than was amoxycillin. After treatment with trovafloxacin at 100 mg/kg bodyweight od for 3 days, a mean log10 cfu of 1.58 and 2.52 L. monocytogenes could be recovered from the spleens and livers, respectively, whereas after treatment with amoxycillin at 100 mg/kg bodyweight every 8 h for 3 days, the mean 1og10 cfu values were 2.36 and 2.02, respectively. These differences were statistically not significant. Results of the present study show that the antibacterial efficacy of trovafloxacin against L. monocytogenes in our animal model is equivalent to that of amoxycillin.

Efficacy of trovafloxacin in an in vitro pharmacodynamic simulation of an intraabdominal infection

An in vitro model simulating trovafloxacin concentrations in human serum after standard doses was used to investigate the activity of this drug with time against Bacteroides fragilis, Escherichia coli, Enterococcus faecalis and Staphylococcus aureus. Antibiotic concentrations used for each incubation period were: 4.24 mg/l (0-1 h), 3.69 mg/l (1-3 h), 3.25 mg/l (3-6 h), 2.38 mg/l (6-8 h), 1.35 mg/l (8-24 h). A 99.9% initial inoculum reduction (> 3 log10 cfu/ml) was defined as bactericidal activity. Bactericidal activity against these organisms was obtained with trovafloxacin after the first hour of incubation, and similar activity was obtained against B. fragilis, E. faecalis and S. aureus after 3 h, when they were tested individually. When the strains were tested as mixed culture, there was bactericidal activity against E. coli after 1 h incubation and after 3 h for S. aureus. This activity was observed against B. fragilis and E. faecalis after 6 h incubation in the mixed culture assays and after 3 h when organisms were tested individually. Regrowth was not observed over a 24 h period. These data show that trovafloxacin might be effective in intraabdominal infections caused by mixed aerobic and anaerobic microorganisms.

Determination of trovafloxacin in human body fluids by high-performance liquid chromatography

For the quantitative determination of trovafloxacin (a new naphthyridinone antibacterial agent) in serum and urine a simple isocratic HPLC method with fluorimetric detection is described. Serum was deproteinised with a mixture of acetonitrile and perchloric acid. The protein-free extract was separated on a reversed-phase column (Nucleosil 100-5 C18) and quantified by means of fluorescence (excitation 275 nm, emission 405 nm). The mobile phase consisted of a mixture of 250 ml acetonitrile and 750 ml distilled water containing 10 mmol/l tetrabutylammonium phosphate. Urine was diluted with 0.25 mol/l phosphoric acid 1:20 (v/v) which was adjusted to pH 3.6 with sodium hydroxide solution. Diluted urine samples were separated on a cation-exchange column (Nucleosil 100-5 SA) and also detected by means of fluorescence. Trovafloxacin was sufficiently separated from endogenous compounds. Results of validation are given. The method was applied successfully to a study of healthy volunteers.

Pharmacodynamics of trovafloxacin in a mouse model of cephalosporin-resistant Streptococcus pneumoniae pneumonia

Trovafloxacin is a potentially useful agent for treatment of infections caused by cephalosporin-resistant Streptococcus pneumoniae. We studied the effectiveness of trovafloxacin therapy and examined the correlation between pharmacodynamic indices in serum and lung, and bacterial killing. Immunocompetent Balb/c mice were infected by intranasal inoculation of a cephalosporin-resistant S. pneumoniae isolate (MIC of ceftriaxone and trovafloxacin 2 and 0.06 mg/L, respectively). Trovafloxacin 10-30 mg/kg/day in one or three divided doses was started 15 h after infection. Serum and lung drug concentrations were measured at multiple time points for 24 h. Serum concentrations peaked at 30-60 min and lung concentrations approximately 30 min later. The serum T1/2 was approximately 9 h and lung T1/2 varied from 5 to 9 h. Lung AUC and Cmax values were 2-3 times greater than those in serum. At the start of therapy lung bacterial concentrations were 8.4 +/- 0.3 log10 cfu/mL and 24 h later had decreased by 3.5 +/- 0.2, 4.0 +/- 0.2, 0.8 +/- 0.3 and 1.0 +/- 1.2 log10 cfu/mL with 30 mg/kg x 1, 10 mg/kg x 3, 10 mg/kg x 1 and 3.3 mg/kg x 3 regimens, respectively. Although the larger dosages were more effective (P < 0.001) the differences between divided and single dosage regimens were not significant. Trovafloxacin serum AUC/MIC ratio correlated best with bacterial killing in the lungs over 24 h. Trovafloxacin is likely to be useful in the treatment of cephalosporin-resistant S. pneumoniae pneumonia.

Nonlinear models for in vitro kill kinetics of antibiotics

In this study, we developed nonlinear regression models to analyze the data generated from an in vitro continuous culture system to assess the kinetics of metronidazole and trovafloxacin in inhibiting the growth of Bacteroides fragilis. The model includes parameters describing the initial shock effect of an antibiotic pulse, the overall antibiotic wash-out rate from the system, and the long-term toxicity of the antibiotic in the environment after one pulse and before the next pulse.

Pharmacodynamics of trovafloxacin, ofloxacin, and ciprofloxacin against Streptococcus pneumoniae in an in vitro pharmacokinetic model

An in vitro pharmacokinetic model was used to simulate the pharmacokinetics of trovafloxacin, ofloxacin, and ciprofloxacin in human serum and to compare their pharmacodynamics against eight Streptococcus pneumoniae strains. The MICs of ofloxacin and ciprofloxacin ranged from 1 to 2 micrograms/ml. Trovafloxacin was 8- to 32-fold more potent, with MICs of 0.06 to 0.12 microgram/ml. Logarithmic-phase cultures were exposed to peak concentrations of trovafloxacin, ofloxacin, or ciprofloxacin achieved in human serum after 200-, 400-, and 750-mg oral doses, respectively. Trovafloxacin was dosed at 0 and 24 h, and ofloxacin and ciprofloxacin were dosed at 0, 12, and 24 h. Human elimination pharmacokinetics were simulated, and viable bacterial counts were measured at 0, 2, 4, 6, 8, 12, 24, and 36 h. Trovafloxacin was rapidly and significantly bactericidal against all eight strains evaluated, with viable bacterial counts decreasing at least 5 logs to undetectable levels. Times to 99.9% killing were only 1 to 3 h. Although the rate of killing with ofloxacin was substantially slower than that with trovafloxacin, ofloxacin was also able to eradicate all eight strains from the model, despite a simulated area under the inhibitory curve/MIC ratio (AUC/MIC) of only 49. In contrast, ciprofloxacin eradicated only five strains (AUC/MIC = 44) from the model. Against the other three strains (AUC/MIC = 22), the antibacterial activity of ciprofloxacin was substantially diminished. These data corroborate clinical data and suggest that trovafloxacin has a pharmacodynamic advantage over ciprofloxacin and ofloxacin against S. pneumoniae in relation to its enhanced antipneumococcal activity.

Ethanol feeding does not affect the efficacy or pharmacokinetics of azithromycin, trovafloxacin, or ceftriaxone in a rat model of pneumococcal pneumonia

A rat model of ethanol feeding was used to study the effects of ethanol on antibiotic therapy of pneumococcal pneumonia. Male Sprague-Dawley rats (150 g) received a liquid diet containing 36% of total calories as ethanol. Controls were pair-fed a liquid diet without ethanol or received rat chow. Diets began 7 days pre- and continued postinfection. Rats were infected transtracheally with type 3 Streptococcus pneumoniae and then treated with azithromycin (50 mg/kg), trovafloxacin (50 mg/kg), or ceftriaxone (100 mg/kg) injected subcutaneously twice daily for 5 days. Antibiotic levels in serum, lung cells, and lavage fluid were measured by HPLC. Ethanol- and pair-fed rats had depressed baseline peripheral neutrophil counts but were able to generate adequate numbers of peripheral and pulmonary polymorphonuclear leukocytes early in the course of their infection. Ethanol feeding did not alter the pharmacokinetics of azithromycin, trovafloxacin, or ceftriaxone. All three antibiotics were equally effective in curing experimental pneumococcal pneumonia, and survival rates were similar in treated ethanol-fed and control rats.