Microarray analysis in human hepatocytes suggests a mechanism for hepatotoxicity induced by trovafloxacin.

Idiosyncratic drug toxicity, defined as toxicity that is dose independent, host dependent, and usually cannot be predicted during preclinical or early phases of clinical trials, is a particularly confounding complication of drug development. An understanding of the mechanisms that lead to idiosyncratic liver toxicity would be extremely beneficial for the development of new compounds. We used microarray analysis on isolated human hepatocytes to understand the mechanisms underlying the idiosyncratic toxicity induced by trovafloxacin. Our results clearly distinguish trovafloxacin from other marketed quinolone agents and identify unique gene changes induced by trovafloxacin that are involved in mitochondrial damage, RNA processing, transcription, and inflammation that may suggest a mechanism for the hepatotoxicity induced by this agent. In conclusion, this work establishes the basis for future microarray analysis of new compounds to determine the presence of these expression changes and their usefulness in predicting idiosyncratic hepatotoxicity. Supplementary material for this article can be found on the HEPATOLOGY website (http://interscience. Wiley.com/jpages/0270-9139/suppmat/index.htnd).

Parent-reported outcomes for treatment of acute otitis media with cefdinir or amoxicillin/clavulanate oral suspensions.

OBJECTIVE: To compare parent-reported outcomes (satisfaction, tolerability, compliance, and work/daycare missed) for children (aged 6 months to 6 years) receiving either cefdinir or amoxicillin/clavulanate for acute otitis media. METHOD: In a phase IV, investigator-blinded, parallel-group, randomized, multicenter study, parents or legal guardians were asked to complete the Otitis Parent Questionnaire (OPQ) 12-14 days after the first dose of cefdinir or amoxicillin/clavulanate oral suspensions. Responses in each of the outcome domains were analyzed using non-parametric statistical analysis. RESULTS: Of 367 parents/guardians who completed the questionnaire, better ease of use (p = 0.009) and taste (p < 0.0001) were associated with cefdinir versus amoxicillin/clavulanate treatment, and children were significantly more likely to experience vomiting with amoxicillin/clavulanate (16% vs 8%; p = 0.016). Parents also reported that their children were much more likely to take all of their medication if receiving cefdinir (68% vs 53% for amoxicillin/clavulanate; p = 0.005). There were no statistically significant differences between groups in work/daycare missed. CONCLUSION: Based on parents' assessment using the OPQ, cefdinir was easier to administer and tasted better than amoxicillin/clavulanate. Children who received cefdinir also experienced less vomiting and had greater compliance than children who received amoxicillin/clavulanate.

Comparison of five-day cefdinir treatment with ten-day low dose amoxicillin/clavulanate treatment for acute otitis media.

BACKGROUND: Short course beta-lactam antibiotic therapy for acute otitis media (AOM) should improve patient adherence, but it has not been evaluated since the heptavalent pneumococcal conjugate vaccine became routinely used in the United States. METHODS: In a prospective, investigator-blinded, multicenter study, 425 patients, age 6 months-6 years, with a clinical diagnosis of nonrefractory AOM were randomized to receive either 5 days of cefdinir therapy (14 mg/kg divided twice daily) or 10 days of amoxicillin/clavulanate therapy (45/6.4 mg/kg divided twice daily). Clinical response was assessed at end of therapy (2-4 days postantibiotic, respectively) and week 4 (study days 25-28). RESULTS: With no difference in demographics between treatment groups, overall the mean age (+/-SD) was 2.8 +/- 1.8 years, 65% had received conjugated pneumococcal vaccination and 48% had bilateral AOM. The satisfactory clinical response rate at end of therapy was comparable for cefdinir versus amoxicillin/clavulanate (88%, 170 of 194 versus 85%, 164 of 192; 95% CI -4.9, 9.3). Although this must be interpreted with caution, cefdinir showed an apparent trend for higher efficacy than amoxicillin/clavulanate (92%, 72 of 78 versus 77%, 55 of 71; P = 0.019) in a subsample of patients 6-24 months old who had received conjugated pneumococcal vaccination. The incidence of drug-related adverse events was less for cefdinir than for amoxicillin/clavulanate (24%, 50 of 211 versus 38%, 82 of 214; P = 0.0018) CONCLUSION: For children with nonrefractory AOM, based only on clinical endpoints, 5 days of therapy with cefdinir 14 mg/kg divided twice daily was comparable overall with 10 days of therapy with low dose amoxicillin/clavulanate 45/6.4 mg/kg divided twice daily.

CYP3A5 genotype has a dose-dependent effect on ABT-773 plasma levels.

BACKGROUND: The metabolizing enzyme cytochrome P450 (CYP) 3A5 is polymorphically expressed as a result of genetic variants that do not encode functional protein. Because of overlapping substrate specificity with CYP3A4 and the multidrug efflux pump P-glycoprotein, the importance of CYP3A5 genetic polymorphism for pharmacokinetics is controversial. OBJECTIVE: Our objective was to determine whether genetic polymorphisms in CYP3A5 or MDR-1 (which encodes P-glycoprotein) influence the drug levels of ABT-773, a ketolide antibiotic that is a substrate for both CYP3A and P-glycoprotein. METHODS: Healthy volunteers given 3 different oral dose levels of ABT-773 were genotyped at 2 common CYP3A5 and 7 common MDR-1 polymorphisms. Individuals were categorized as CYP3A5-positive if they carried at least 1 functional CYP3A5*1 allele and as CYP3A5-negative if they did not. Area under the plasma concentration-time curves (AUCs) from 0 to 6 hours (AUC(t)) and maximum postdose plasma concentration (C(max)) after a single dose and on day 5 of a twice-daily regimen were calculated and correlated with genotypes. RESULTS: ABT-773 AUC(t) and C(max) were, on average, higher in CYP3A5-negative subjects given 450 mg ABT-773 (n = 9) than in CYP3A5-positive subjects with identical doses (n = 8). The relationship for AUC(t) was statistically significant both after a single dose (geometric mean and 95% confidence interval [CI], 5.0 microg.h/mL [3.9-6.4 microg.h/mL] versus 2.8 microg.h/mL [1.8-4.3 microg.h/mL]; P =.03) and on the fifth day of twice-daily dosing (12.4 microg.h/mL [8.7-17.6 microg.h/mL] versus 7.4 microg.h/mL [5.5-9.8 microg.h/mL], P =.04). The relationship for C(max) was statistically significant after a single dose (1220 microg/mL [867-1167 microg/mL] versus 727 microg/mL [506-1044 microg/mL], P =.04) and showed a trend in the same direction on the fifth day of twice-daily dosing (2566 microg/mL [1813-3631 microg/mL] versus 1621 microg/mL [1122-2343 microg/mL], P =.07). In contrast, AUC(t) and C(max) were not significantly different between CYP3A5-positive and CYP3A5-negative individuals given 150 mg or 300 mg ABT-773. ABT-773 plasma levels did not trend with MDR-1 genotypes. CONCLUSIONS: These results suggest that CYP3A5 genotype may be an important determinant of in vivo drug disposition and that this effect may be dose-dependent.

Susceptibility of Bacillus anthracis to eleven antimicrobial agents including novel fluoroquinolones and a ketolide.

OBJECTIVES: To determine the susceptibility of southern African strains of Bacillus anthracis to new, investigational agents as well as conventional antibiotics. MATERIALS AND METHODS: The MICs of 26 isolates of B. anthracis from South Africa and Zimbabwe, as well as the Sterne vaccine strain and a type culture strain, were determined by agar dilution. RESULTS: The most active antimicrobial agents were the novel ketolide ABT 773, new and conventional fluoroquinolones, and doxycycline; macrolides were intermediately active. The lack of activity of extended-spectrum cephalosporins against B. anthracis was confirmed. CONCLUSIONS: Susceptibility to conventional antibiotics was in keeping with previous studies. Two new fluoroquinolones and a ketolide showed promising in vitro activity that would support their further evaluation in animal models of anthrax.

Susceptibility of Yersinia pestis to novel and conventional antimicrobial agents.

OBJECTIVES: To determine the susceptibility of southern African strains of Yersinia pestis to novel as well as conventional antimicrobial agents. MATERIALS AND METHODS: The MICs of 28 strains of Yersinia pestis from a southern African plague focus were determined by agar dilution. RESULTS: The most active agents were cefditoren and the fluoroquinolones, both conventional and novel. The in vitro activity of macrolides was poor against this member of the Enterobacteriaceae. CONCLUSION: Further investigation of the novel quinolones olamufloxacin (HSR 903) and ABT 492 in animal models of plague would seem to be justified.

Microbiological efficacy of ABT-773 (cethromycin) for the treatment of community-acquired pneumonia due to Chlamydia pneumoniae.

Nasopharyngeal specimens for culture of Chlamydia pneumoniae were obtained from patients with community-acquired pneumonia enrolled in a randomized study comparing the novel ketolide antibiotic ABT-773 at a dose of 150 mg once a day to 150 mg twice a day, by mouth for 10 days. C. pneumoniae was eradicated from the nasopharynx of 10 of 10 (100%) microbiologically evaluable patients. MICs and MBCs for 13 isolates of C. pneumoniae from 12 patients obtained before and after therapy were performed against ABT-773. The MIC90 and MBC90 of ABT-773 were 0.015 mg/L.