Short-course versus long-course therapy of the same antibiotic for community-acquired pneumonia in adolescent and adult outpatients.

BACKGROUND: Community-acquired pneumonia (CAP) is a lung infection that can be acquired during day-to-day activities in the community (not while receiving care in a hospital). Community-acquired pneumonia poses a significant public health burden in terms of mortality, morbidity, and costs. Shorter antibiotic courses for CAP may limit treatment costs and adverse effects, but the optimal duration of antibiotic treatment is uncertain. OBJECTIVES: To evaluate the efficacy and safety of short-course versus longer-course treatment with the same antibiotic at the same daily dosage for CAP in non-hospitalised adolescents and adults (outpatients). We planned to investigate non-inferiority of short-course versus longer-term course treatment for efficacy outcomes, and superiority of short-course treatment for safety outcomes. SEARCH METHODS: We searched CENTRAL, which contains the Cochrane Acute Respiratory Infections Group Specialised Register, MEDLINE, Embase, five other databases, and three trials registers on 28 September 2017 together with conference proceedings, reference checking, and contact with experts and pharmaceutical companies. SELECTION CRITERIA: Randomised controlled trials (RCTs) comparing short- and long-courses of the same antibiotic for CAP in adolescent and adult outpatients. DATA COLLECTION AND ANALYSIS: We planned to use standard Cochrane methods. MAIN RESULTS: Our searches identified 5260 records. We did not identify any RCTs that compared short- and longer-courses of the same antibiotic for the treatment of adolescents and adult outpatients with CAP.We excluded two RCTs that compared short courses (five compared to seven days) of the same antibiotic at the same daily dose because they evaluated antibiotics (gemifloxacin and telithromycin) not commonly used in practice for the treatment of CAP. In particular, gemifloxacin is no longer approved for the treatment of mild-to-moderate CAP due to its questionable risk-benefit balance, and reported adverse effects. Moreover, the safety profile of telithromycin is also cause for concern.We found one ongoing study that we will assess for inclusion in future updates of the review. AUTHORS' CONCLUSIONS: We found no eligible RCTs that studied a short-course of antibiotic compared to a longer-course (with the same antibiotic at the same daily dosage) for CAP in adolescent and adult outpatients. The effects of antibiotic therapy duration for CAP in adolescent and adult outpatients remains unclear.

Antimicrobials and QT prolongation.

Solithromycin, a ketolide/macrolide antibiotic, has recently been reported to be free of the expected QT-prolonging effect of macrolides. It appears that its keto substitution provides a structural basis for this observation, as the other two tested ketolides also have minimal QT effect.Among non-cardiovascular therapies, antimicrobials probably carry the greatest potential to cause cardiac arrhythmias. This is a result of their propensity to bind to the delayed rectifier potassium channel, IKr, inducing QT prolongation and risk of torsades de pointes ventricular tachycardia, their frequent interference with the metabolism of other QT prolongers and their susceptibility to metabolic inhibition by numerous commonly used drugs.Unfortunately, there is evidence that medical practitioners do not take account of the QT/arrhythmia risk of antimicrobials in their prescribing practices. Education on this topic is sorely needed. When a macrolide is indicated, a ketolide should be considered in patients with a QT risk.

Synergistic effects and antibiofilm properties of chimeric peptides against multidrug-resistant Acinetobacter baumannii strains.

The increasing prevalence of drug-resistant pathogens highlights the need to identify novel antibiotics. Here we investigated the efficacies of four new antimicrobial peptides (AMPs) for potential drug development. The antibacterial activities, synergistic effects, and antibiofilm properties of the four chimeric AMPs were tested against Acinetobacter baumannii, an emerging Gram-negative, nosocomial, drug-resistant pathogen. Nineteen A. baumannii strains resistant to ampicillin, cefotaxime, ciprofloxacin, tobramycin, and erythromycin were isolated at a hospital from patients with cholelithiasis. All four peptides exhibited significant antibacterial effects (MIC=3.12 to 12.5 µM) against all 19 strains, whereas five commercial antibiotics showed little or no activity against the same pathogens. An exception was polymyxin, which was effective against all of the strains tested. Each of the peptides showed synergy against one or more strains when administered in combination with cefotaxime, ciprofloxacin, or erythromycin. The peptides also exhibited an ability to prevent biofilm formation, which was not seen with cefotaxime, ciprofloxacin, or erythromycin, though polymyxin also inhibited biofilm formation. Indeed, when administered in combination with ciprofloxacin, the AMP HPMA exerted a potent synergistic effect against A. baumannii biofilm formation. Collectively, our findings indicate that the AMPs tested have no cytotoxicity but possess potent antibacterial and antibiofilm activities and may act synergistically with commercial antibiotics.

Pharmacokinetic modelling of serum and bronchial concentrations for clarithromycin and telithromycin, and site-specific pharmacodynamic simulation for their dosages.

WHAT IS KNOWN AND OBJECTIVE: Clinical pharmacokinetic profiles of clarithromycin and telithromycin in bronchopulmonary sites have not been fully characterized. This study aimed to describe in more detail the pharmacokinetics of the two macrolides in epithelial lining fluid (ELF) of human bronchi and to evaluate their pharmacodynamic target attainment at this site. METHODS: Previously reported drug concentration data for serum and ELF were simultaneously fitted to a three-compartment pharmacokinetic model using nonmem program. The model parameter estimates were used for site-specific pharmacodynamic simulation. RESULTS AND DISCUSSION: Population mean parameters for clarithromycin were as follows: distribution volumes of central, peripheral and ELF compartments (V1 /F, V2 /F and V3 /F) = 204·7, 168·9 and 67·1 L; clearance (CL/F) = 34·4 L/h; absorption rate constant (Ka ) = 0·680 1/h; transfer rate constants connecting compartments (K12 , K21 , K13 and K31  = 0·0193, 0·434, 0·667 and 0·260 1/h, respectively). Mean parameters for telithromycin were as follows: V1 /F, V2 /F and V3 /F = 370·3, 290·3 and 213·8 L; CL/F = 89·5 L/h; Ka  = 0·740 1/h; K12 , K21 , K13 and K31  = 0·0026, 1·044, 0·758 and 0·158 1/h, respectively. Using these parameters, the mean ELF/serum ratio in the area under drug concentration-time curve (AUC) was 7·80 for clarithromycin and 8·05 for telithromycin. Clarithromycin achieved a ≥ 90% probability of attaining a pharmacodynamic target [AUC/minimum inhibitory concentration (MIC) = 100] in ELF against bacterial isolates for which MICs were ≤0·5 and ≤1 mg/L for twice-daily doses of 250 and 500 mg, respectively. For telithromycin, once-daily doses of 600 and 800 mg achieved a ≥90% probability in ELF against Streptococcus pneumoniae, Staphylococcus aureus and Moraxella catarrhalis isolates but not Haemophilus influenzae isolates. WHAT IS NEW AND CONCLUSION: These results should provide a better understanding of the bronchial pharmacokinetics of clarithromycin and telithromycin, while also providing useful information about their dosages for respiratory tract infections based on site-specific pharmacodynamic evaluation. Further studies in a large number of patients are needed to confirm our findings and clarify their therapeutic implications.

Involvement of intestinal permeability in the oral absorption of clarithromycin and telithromycin.

The involvement of intestinal permeability in the oral absorption of clarithromycin (CAM), a macrolide antibiotic, and telithromycin (TEL), a ketolide antibiotic, in the presence of efflux transporters was examined. In order independently to examine the intestinal and hepatic availability, CAM and TEL (10 mg/kg) were administered orally, intraportally and intravenously to rats. The intestinal and hepatic availability was calculated from the area under the plasma concentration-time curve (AUC) after administration of CAM and TEL via different routes. The intestinal availabilities of CAM and TEL were lower than their hepatic availabilities. The intestinal availability after oral administration of CAM and TEL increased by 1.3- and 1.6-fold, respectively, after concomitant oral administration of verapamil as a P-glycoprotein (P-gp) inhibitor. Further, an in vitro transport experiment was performed using Caco-2 cell monolayers as a model of intestinal epithelial cells. The apical-to-basolateral transport of CAM and TEL through the Caco-2 cell monolayers was lower than their basolateral-to-apical transport. Verapamil and bromosulfophthalein as a multidrug resistance-associated proteins (MRPs) inhibitor significantly increased the apical-to-basolateral transport of CAM and TEL. Thus, the results suggest that oral absorption of CAM and TEL is dependent on intestinal permeability that may be limited by P-gp and MRPs on the intestinal epithelial cells.

Pharmacokinetic interaction between telithromycin and metformin in diabetes mellitus rats.

Telithromycin and metformin have been reported to be commonly metabolized via hepatic CYP3A1/2 in rats. Community-acquired respiratory tract infection was reported to be frequent in patients with diabetes mellitus. Compared with controls, hepatic CYP3A1/2 was reported to be increased in male rats with diabetes mellitus induced by streptozotocin (DMIS rats). After the intravenous administration of both drugs together to male DMIS rats, the time-averaged non-renal clearance (CL(NR)) of metformin was significantly slower (by 33.1%; 10.3 versus 15.4 ml min(-1) kg(-1)) than metformin alone due to the inhibition of hepatic metabolism of metformin by telithromycin via CYP3A1/2. After the oral administration of both drugs together, the total area under the plasma concentration-time curve (AUC) of metformin was comparable possibly due to the increased intestinal metabolism of metformin by telithromycin.

Aerosol-based efficient delivery of telithromycin, a ketolide antimicrobial agent, to lung epithelial lining fluid and alveolar macrophages for treatment of respiratory infections.

PURPOSE: The efficacy of aerosol-based delivery of telithromycin (TEL), as a model antimicrobial agent, for the treatment of respiratory infections was evaluated by comparison with oral administration. METHOD: The aerosol formulation (0.2 mg/kg) was administered to rat lungs using a Liquid MicroSprayer. RESULTS AND DISCUSSION: The time courses of the concentration of TEL in lung epithelial lining fluid (ELF) and alveolar macrophages (AMs) following administration of an aerosol formulation to rat lungs were markedly higher than that following the administration of an oral formulation (50 mg/kg). The time course of the concentrations of TEL in plasma following administration of the aerosol formulation was markedly lower than that in ELF and AMs. These results indicate that the aerosol formulation is more effective in delivering TEL to ELF and AMs, compared to the oral formulation, despite a low dose and it avoids distribution of TEL to the blood. In addition, the antibacterial effects of TEL in ELF and AMs following administration of the aerosol formulation were estimated by pharmacokinetics/pharmacodynamics analysis. The concentrations of TEL in ELF and the AMs time curve/minimum inhibitory concentration of TEL ratio were markedly higher than the effective values. CONCLUSION: This study indicates that an antibiotic aerosol formulation may be an effective pulmonary drug delivery system for the treatment of respiratory infections.

Subinhibitory concentrations of telithromycin, clarithromycin and azithromycin reduce methicillin-resistant Staphylococcus aureus coagulase in vitro and in vivo.

BACKGROUND: Subinhibitory levels of clarithromycin and azithromycin have been shown to reduce the activity of bacterial virulence factors, but few studies have examined the effects of subinhibitory levels of telithromycin. Here, we examined the effects of telithromycin, clarithromycin and azithromycin on methicillin-resistant Staphylococcus aureus (MRSA) coagulase in vitro. We also examined the effects of these antibiotics on bacterial survival in a murine model of pulmonary infection, in which the number of bacteria in the lung correlates with the coagulase titre. METHODS: The coagulase titre in MRSA strain NUMR101, a clinical isolate, was measured after a 16 h treatment with telithromycin, clarithromycin or azithromycin at the MIC (512 mg/L) and 1/2, 1/4, 1/8 and 1/16 of the MIC. In addition, we examined the effect of these drugs in a murine model of pulmonary infection induced by the intravenous injection of S. aureus enmeshed in agar beads. Treatment was started 1 day before infection and mice were treated once a day for 7 days by oral administration of 10 or 100 mg/kg telithromycin, clarithromycin or azithromycin, and the number of viable bacteria in the lungs was counted 24 h after the injection of the bacteria. RESULTS: The coagulase titres in mice treated with 1/8 of the MIC of telithromycin, clarithromycin and azithromycin and in the control were 8, 4, 8 and 32, respectively. In the mouse model of infection, the log cfu/lung (mean +/- SEM; n = 5 or 6) were 6.62 +/- 0.81, 4.79 +/- 0.41, 6.15 +/- 0.38 and 8.41 +/- 0.30 for mice treated with 100 mg/kg/day of telithromycin, clarithromycin and azithromycin and for controls, respectively (P < 0.05 for all groups versus control). CONCLUSIONS: Subinhibitory concentrations of telithromycin inhibit MRSA coagulase in vitro. In addition, the in vivo results indicate that pre-treatment with telithromycin, clarithromycin or azithromycin can reduce the bacterial load in a murine model of pulmonary infection.

Role of p-glycoprotein inhibition for drug interactions: evidence from in vitro and pharmacoepidemiological studies.

OBJECTIVES: We determined in vitro the potency of macrolides as P-glycoprotein inhibitors and tested in hospitalised patients whether coadministration of P-glycoprotein inhibitors leads to increased serum concentrations of the P-glycoprotein substrates digoxin and digitoxin. METHODS: In vitro, the effect of macrolides on polarised P-glycoprotein-mediated digoxin transport was investigated in Caco-2 cells. In a pharmacoepidemiological study, we analysed the serum digoxin and digitoxin concentrations with and without coadministration of P-glycoprotein inhibitors in hospitalised patients. RESULTS: All macrolides inhibited P-glycoprotein-mediated digoxin transport, with concentrations producing 50% inhibition (IC(50)) values of 1.8, 4.1, 15.4, 21.8 and 22.7 micromol/L for telithromycin, clarithromycin, roxithromycin, azithromycin and erythromycin, respectively. Coadministration of P-glycoprotein inhibitors was associated with increased serum concentrations of digoxin (1.3 +/- 0.6 vs 0.9 +/- 0.5 ng/mL, p < 0.01). Moreover, patients receiving macrolides had higher serum concentrations of cardiac glycosides (p < 0.05). CONCLUSION: Macrolides are potent inhibitors of P-glycoprotein. Drug interactions between P-glycoprotein inhibitors and substrates are likely to occur during hospitalisation.

Human serum activity of telithromycin, azithromycin and amoxicillin/clavulanate against common aerobic and anaerobic respiratory pathogens.

Telithromycin is a new ketolide antimicrobial with a good in vitro activity against both aerobic and anaerobic respiratory pathogens. In this study, we evaluated the antibacterial activity over time of telithromycin (800mg), azithromycin (500mg), and amoxicillin/clavulanate (875/125mg) in serum following single oral doses of these agents to 10 healthy subjects. Inhibitory and bactericidal titers were determined at 2, 6, 12, and 24h after each dose and the median titer was used to determine antibacterial activity. Against two azithromycin-resistant strains of Streptococcus pneumoniae, both telithromycin (MIC=0.25 and 0.5 microg/mL) and amoxicillin/clavulanate exhibited inhibitory and cidal activity for at least 6h. All three antibiotics provided prolonged (>or=12h) inhibitory activity against strains of Hemophilus influenzae (telithromycin MIC=4.0 microg/ml). Both telithromycin and amoxicillin/clavulanate exhibited rapid and prolonged inhibitory activity (>or=12h) against each of the anaerobes studied (Finegoldia [Peptostreptococcus] magna Peptostreptococcus micros, Prevotella bivia, and Prevotella melaninogenica). Moreover, both agents provided bactericidal activity against both Prevotella species. In this ex vivo pharmacodynamic study, we found that telithromycin provided rapid and prolonged antibacterial activity in serum against macrolide-resistant strains of S. pneumoniae, beta-lactamase-positive and -negative strains of H. influenzae, and common respiratory anaerobic pathogens. These findings suggest that telithromycin could have clinical utility in the treatment of community-acquired mixed aerobic-anaerobic respiratory tract infections, including chronic sinusitis and aspiration pneumonia.

Dose-dependent pharmacokinetics of telithromycin after intravenous and oral administration to rats: contribution of intestinal first-pass effect to low bioavailability.

PURPOSE: To evaluate the pharmacokinetics of telithromycin after intravenous and oral administration and to find the reason for incomplete F value (first pass-effect) after intravenous, intraportal, intragastric, and intraduodenal administration to rats. METHODS: Telithromycin was administered intravenously or orally at doses of 20, 50, and 100 mg/kg to rats. And hepatic, gastric, and intestinal first-pass effects of telithromycin were also measured after intravenous, intraportal, intragastric, and intraduodenal administration at a dose of 50 mg/kg to rats. RESULTS: The dose-normalized AUC values of telithromycin were dose-dependent (increased with increasing doses) after both intravenous and oral dose ranges studied, possibly due to saturable metabolism of telithromycin. After oral administration (50 mg/kg), approximately 4.06% of oral dose was not absorbed, F was approximately 27.5%, and the intestinal first-pass effect was approximately 63.4% of oral dose. The first-pass effects of telithromycin in the lung, heart, stomach, and liver were almost negligible, if any, in rats. CONCLUSIONS: The low F of telithromycin at a dose of 50 mg/kg was mainly due to considerable intestinal first-pass effect, approximately 63.4% of oral dose, in rats.

Clinical and bacteriologic efficacy of telithromycin in patients with bacteremic community-acquired pneumonia.

This retrospective analysis was performed to determine the clinical and bacteriologic efficacy of the ketolide antibacterial telithromycin in patients with community-acquired pneumonia (CAP) with pneumococcal bacteremia. Patients 13 years old with radiologically confirmed CAP and a positive blood culture for Streptococcus pneumoniae at screening were analyzed from eight multicenter Phase III/IV clinical trials. In four open-label, non-comparative studies, patients received telithromycin 800 mg once daily for 7-10 days. In four randomized, controlled, double-blind, comparative studies, patients received telithromycin 800 mg once daily for 5-10 days or a comparator antimicrobial (amoxicillin 1000 mg three times daily, clarithromycin 500 mg twice daily, or trovafloxacin 200 mg once daily) for 7-10 days. In total, 118 patients (telithromycin, 94/1061 [8.9%]; comparator, 24/244 [9.8%]) had documented pneumococcal bacteremia. Those who were treated with telithromycin achieved a clinical cure rate of 90.2% (74/82, per-protocol population); S. pneumoniae was eradicated in 77/82 (93.9%) bacteremic patients who received telithromycin and 15/19 (78.9%) comparator-treated patients. Clinical cure was also observed among telithromycin-treated bacteremic patients who were infected with penicillin- or erythromycin-resistant strains of S. pneumoniae (5/7 and 8/10, respectively). In conclusion, telithromycin achieves high clinical and bacteriologic cure rates in CAP patients with pneumococcal bacteremia.

Telithromycin in the treatment of pneumococcal community-acquired respiratory tract infections: a review.

OBJECTIVES: A pooled analysis of 14 Phase III studies was performed to establish the clinical and bacteriologic efficacy of telithromycin 800 mg once daily in the treatment of pneumococcal community-acquired respiratory tract infections (RTIs). METHODS: Data were examined from 5534 adult/adolescent patients with community-acquired pneumonia (CAP), acute exacerbations of chronic bronchitis (AECB), or acute bacterial sinusitis, who had received telithromycin for 5-10 days or a comparator antibacterial. RESULTS: Streptococcus pneumoniae was identified in 704/2060 (34.2%) bacteriologically evaluable patients. The respective per-protocol clinical cure rates for telithromycin and comparators were 94.3% and 90.0% (CAP); 81.5% and 78.9% (AECB); 90.1% and 87.5% (acute sinusitis); 92.7% and 87.6% (all indications). Clinical cure rates were 28/34 (82.4%) and 5/7, respectively, for penicillin-resistant infections, and 44/52 (84.6%) and 11/14, respectively, for erythromycin-resistant infections. Of 82 patients with pneumococcal bacteremia, 74 (90.2%) were clinically cured after telithromycin treatment, including 5/7 and 8/10 with penicillin- or erythromycin-resistant strains, respectively. Adverse events considered possibly related to study medication were reported by 1071/4045 (26.5%) telithromycin and 505/1715 (29.4%) comparator recipients. These events were generally of mild/moderate severity, and mainly gastrointestinal in nature. CONCLUSIONS: As S. pneumoniae is the leading bacterial cause of community-acquired RTIs, and antibacterial resistance is increasing among this species, these findings support the use of telithromycin as first-line therapy in this setting.

Microbiological assay for the determination of telithromycin in tablets.

This study describes the development and validation of a microbiological assay, applying the cylinder-plate method, for the determination of the antibiotic telithromycin. The microbiological method consisted of a cylinder-plate agar diffusion assay using Micrococcus luteus ATCC 9341 as the test microorganism. The response graphs for standard and sample solutions were linear (r = 0.9987), and no parallelism deviations were detected in the tested concentrations (0.25, 0.5, and 1.0 microg/mL). The interday precision was 2.67%. Recovery values were between 96.75 and 100.91%. A preliminary stability study of telithromycin showed that the microbiological assay is specific for the determination of telithromycin in the presence of its degradation products. The proposed method allows the quantitation of telithromycin in pharmaceutical dosage form and can be used for drug analysis in routine quality control.

Pharmacodynamic analysis of the microbiological efficacy of telithromycin in patients with community-acquired pneumonia.

BACKGROUND AND OBJECTIVE: Telithromycin, a ketolide antibacterial, demonstrates concentration-dependent bactericidal activity against the major pathogens causing community-acquired respiratory tract infections. The objective of this study was to explore the relationships between pharmacokinetic/pharmacodynamic predictor variables, such as area under the plasma concentration-time curve (AUC) over minimum inhibitory concentration (MIC) [AUC/MIC], maximum plasma concentration (C(max)) over MIC (C(max)/MIC) and microbiological outcome from telithromycin therapy for community-acquired pneumonia (CAP). PATIENTS AND METHODS: Data were pooled from five phase III studies of oral telithromycin (800 mg once daily for 7-10 days) for the outpatient treatment of adults with CAP. Only subjects with a single pathogen isolated at baseline, a telithromycin MIC determination and at least one plasma pharmacokinetic sample were included. Bacteriologically modified intent-to-treat (bmITT) and bacteriologically evaluable per protocol (PPb) populations were analysed. Individual AUC and C(max) Bayesian estimates were obtained with a population pharmacokinetic model. Logistic regression, nonparametric smoothing, and classification analysis and regression tree (CART) were used to assess the relationship between AUC/MIC and C(max)/MIC and microbiological outcome by pathogen. RESULTS: The bmITT population included 224 patients (Streptococcus pneumoniae in 113, Haemophilus influenzae in 89 and Staphylococcus aureus in 22). Median telithromycin MIC was 0.015 microg/mL for S. pneumoniae, 2.0 microg/mL for H. influenzae and 0.12 microg/mL for S. aureus, with median AUC/MIC of 907.1, 6.9 and 98.4, and median C(max)/MIC of 172.0, 1.3 and 20.4 for the three pathogens, respectively. Both logistic regression and nonparametric smoothing showed the probability of microbiological cure to be consistently greater than 90% over the observed range of predictor variables. No reliable AUC/MIC or C(max)/MIC breakpoints were identified by CART. CONCLUSION: Telithromycin exhibits near-maximal efficacy against three major pathogens causing CAP at a dose of 800 mg once daily.

Five-day telithromycin once daily is as effective as 10-day clarithromycin twice daily for the treatment of acute exacerbations of chronic bronchitis and is associated with reduced health-care resource utilization.

STUDY OBJECTIVES: To demonstrate equivalence in the clinical efficacy of telithromycin vs clarithromycin treatment of outpatients with acute exacerbations of chronic bronchitis (AECB), and to compare the tolerability and respiratory-related health-care resource utilization associated with these treatment regimens. DESIGN AND PATIENTS: A randomized, double-blind, multicenter, clinical study was conducted at 105 centers in 14 countries. Adult outpatients (age > or = 30 years) received oral telithromycin, 800 mg qd for 5 days (n = 270), or oral clarithromycin, 500 mg bid for 10 days (n = 282), for the treatment of AECB. Clinical and bacteriologic outcomes were assessed at the posttherapy/test-of-cure (TOC) visit (days 17 to 24; per-protocol population). Health-care resource utilization data were collected for each patient by investigators blinded to study medication up to the late posttherapy visit (days 31 to 36). RESULTS: Clinical cure rates at the posttherapy/TOC visit were comparable between the groups (telithromycin, 193 of 225 patients [85.8%]; clarithromycin, 206 of 231 patients [89.2%]); bacteriologic outcome was satisfactory for 59 of 72 telithromycin-treated patients (81.9%) vs 63 of 76 clarithromycin-treated patients (82.9%). Health-care resource utilization assessed up to the late posttherapy visit was lower in the telithromycin treatment group than the clarithromycin treatment group, with significantly fewer hospitalizations for respiratory-related causes (one hospitalization vs eight hospitalizations for a total of 4 inpatient days vs 39 inpatient days, respectively), significantly fewer AECB-related emergency department visits (0 vs 8), and fewer unscheduled outpatient visits (11 vs 18). Fewer telithromycin-treated patients reported days lost from work (21 of 91 patients [23.1%]; 133 days) compared with those receiving clarithromycin (30 of 98 patients [30.6%]; 141 days). Telithromycin was well tolerated; adverse events considered possibly related to study medication were reported by 61 of 269 patients (22.7%) and 100 of 280 patients (35.7%) receiving telithromycin and clarithromycin, respectively. CONCLUSIONS: In this study, 5-day telithromycin treatment was as effective and well tolerated as 10-day clarithromycin treatment for patients with AECB, and was associated with a reduced utilization of health-care resources.

Pharmacodynamics of an 800-mg dose of telithromycin in patients with community-acquired pneumonia caused by extracellular pathogens.

The pharmacodynamics of telithromycin, a new ketolide antibacterial, was examined in 115 patients with community-acquired pneumonia (CAP). Patients received telithromycin 800 mg qd for 7-10 days. Pharmacokinetic parameters were determined, and exposure was linked to microbiological outcome using logistic regression analysis. A breakpoint for increased probability of microbiological eradication was developed and was found to be the ratio of area under the concentration-time curve (AUC) to minimum inhibitory concentration (MIC) of 3.375. The final logistic regression model of microbiological outcome included body weight and AUC/MIC ratio breakpoint. This model was found in analyses of the entire population and when Streptococcus pneumoniae and Haemophilus influenzae were examined separately. The AUC/MIC ratio target attainment rate is expected to be >99.9% for S. pneumoniae and Moraxella catarrhalis and 93.1% for H. influenzae. This study demonstrated a relationship between telithromycin drug exposure and microbiological outcome. Telithromycin is expected to achieve the drug exposure breakpoint for the majority of isolates causing CAP.

The bioequivalence of telithromycin administered orally as crushed tablets versus tablets swallowed whole.

This open-label, randomized, crossover study was conducted to demonstrate bioequivalence for telithromycin administered as crushed or whole tablets. Single 800-mg telithromycin doses (2x400-mg tablets) were administered as crushed tablets mixed in 240 mL nutritional supplement drink followed by 120 mL water or as whole tablets swallowed with 240 mL water. Plasma telithromycin concentrations were measured by liquid chromatography/mass spectrometry; pharmacokinetic parameters were determined using noncompartmental methods. Average bioequivalence criteria were applied. Thirty-two subjects received telithromycin by both methods. The 90% confidence intervals for the geometric mean ratios of maximum plasma concentration and area under the plasma concentration-time curve to 24 hours were within the 0.80 to 1.25 range. Median tmax was 3.00 hours for both treatments. Both methods of administration were well tolerated. Crushing telithromycin tablets and administering them with a nutritional supplement drink is bioequivalent to ingesting whole tablets and could be a viable method of administration for patients unable to swallow tablets whole.

Assessment of the efficacy of telithromycin simulating human exposures against S. pneumoniae with ribosomal mutations in a murine pneumonia model.

Telithromycin (TEL) is a ketolide antimicrobial agent with in vitro activity against Streptococcus pneumoniae (SPN), including macrolide resistant strains. The purpose of this study was to assess the efficacy of TEL against clinical SPN isolates with various genotypic mutations including the newly recognized ribosomal mutations. Pneumonia was induced in either immunocompetent and immunosuppressed mice. Six isolates were included in the study and all were resistant to azithromycin (AZI) by MIC testing. Three oral regimens of TEL were chosen to simulate the human pharmacokinetic (PK) exposures observed in young healthy, healthy elderly (> or =65 years), and infected subjects. An additional group was given AZI in human simulated doses. Bacterial density in lung was determined after each treatment. Telithromycin administered simulating infected patients showed greater efficacy (i.e., change in logCFU) than the azithromycin treated group for all isolates except P1660008. The immune system was responsible for increased efficacy (ranging from 45-146%) for all but one of the telithromycin treatment regimens. Unlike other isolates studied in this in vivo model, P1660008 displayed a highly variable response to therapy, such that the reductions in CFU were not consistent with the microbiological and PK profiles of either compound. For all other isolates, the activity of AZI was comparable with untreated controls. Human simulated exposures of TEL displayed 0.5-3.4 log kill in vivo despite the ribosomal mutations studied. These data support the in vivo efficacy of TEL against a variety of genotypic resistance profiles observed in pneumococci, however, additional studies are required to fully characterize the killing profile of the compound against these recently determined ribosomal mutations.

Bacteriological efficacy of 5-day therapy with telithromycin in acute maxillary sinusitis.

Increasing resistance among the key pathogens responsible for community-acquired respiratory tract infections, namely Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis, has the potential to limit the effectiveness of the antibacterial agents available to treat these infections. Moreover, there are regional differences in the susceptibility patterns observed and, as treatment is usually empirical, choosing an effective treatment can be challenging. Telithromycin, the first ketolide to be approved for clinical use, offers an activity profile that covers the key respiratory pathogens including penicillin- and macrolide-resistant S. pneumoniae as well as beta-lactamase-producing H. influenzae and M. catarrhalis. In a pooled analysis of three large controlled clinical trials involving patients with acute maxillary sinusitis, the bacteriological efficacy of 5- or 10-day treatment with telithromycin and 10-day treatment with comparators was evaluated. Telithromycin administered as a once-daily 800 mg dose for 5 days achieved eradication rates of 91.8, 87.5 and 92.9% for S. pneumoniae, H. influenzae and M. catarrhalis, respectively. Bacteriological eradication of 8/10 and 12/14 isolates of S. pneumoniae resistant to penicillin and erythromycin, respectively, was also reported following 5-day treatment with telithromycin. The clinical efficacy of this regimen was equivalent to that of a 10-day regimen of telithromycin or standard 10-day courses of amoxicillin-clavulanic acid or cefuroxime axetil. Telithromycin 800mg given for 5 days was well tolerated, with the majority of adverse events being of mild or moderate intensity. These data suggest that telithromycin provides effective first-line therapy for use in patients with acute maxillary sinusitis in a short and convenient once-daily dosage regimen.