Telithromycin 800 mg once daily for seven to ten days is an effective and well-tolerated treatment for community-acquired pneumonia

Etiology of community-acquired pneumonia in adults: a systematic review

Background

The etiology of community-acquired pneumonia (CAP) has evolved since the beginning of the antibiotic era. Recent guidelines encourage immediate empiric antibiotic treatment once a diagnosis of CAP is made. Concerns about treatment recommendations, on the one hand, and antibiotic stewardship, on the other, motivated this review of the medical literature on the etiology of CAP.

Methods

We conducted a systematic review of English-language literature on the etiology of CAP using methods defined by the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. We searched PubMed using a combination of the keywords ‘pneumonia’, ‘CAP’, ‘etiology’, ‘microbiology’, ‘bacteriology’, and ‘pathogen’. We examined articles on antibiotics that were develop to treat pneumonia. We reviewed all ‘related articles’ as well as studies referenced by those that came up in the search. After we excluded articles that did not give sufficient microbiological data or failed to meet other predetermined criteria, 146 studies remained. Data were stratified into diagnostic categories according to the microbiologic studies that were done; results are presented as the percentage in each category of all cases in which an etiology was established.

Results

Streptococcus pneumoniae remains the most common cause of CAP although declining in incidence; this decline has been greater in the US than elsewhere. Haemophilus influenzae is the second most common cause of CAP, followed by Staphylococcus aureus and Gram negative bacilli. The incidence of all bacteria as causes of CAP has declined because, with routine use of PCR for viruses, the denominator, cases with an established etiology, has increased. Viruses were reported on average in about 10% of cases, but recent PCR-based studies identified a respiratory virus in about 30% of cases of CAP, with substantial rates of viral/bacterial coinfection.

Conclusion

The results of this study justify current guidelines for initial empiric treatment of CAP. With pneumococcus and Haemophilus continuing to predominate, efforts at antibiotic stewardship might be enhanced by greater attention to the routine use of sputum Gram stain and culture. Because viral/bacterial coinfection is relatively common, the identification of a virus by PCR does not, by itself, allow for discontinuation of the antibiotic therapy.

Telithromycin

Telithromycin (Ketek), Aventis Pharma), a ketolide, belongs to a new class of antibiotics that was developed for the treatment of upper and lower respiratory tract infections. The prevalence of penicillin and macrolide resistance among respiratory pathogens is increasing in the USA. Telithromycin is highly active against beta-lactam, macrolide and fluoroquinolone reduced-susceptibility pathogens. Its efficacy has been shown to be equal or superior to comparator agents in numerous studies. It has a broad in vitro spectrum versus usual respiratory pathogens and oral once-daily dosing that increases patient compliance. Telithromycin penetrates rapidly into neutrophils in bronchopulmonary tissue, with peak levels obtained in 1 to 2 h. Results of clinical trials show clinical-esponse rates similar to comparator agents. The most frequent adverse events involve the gastrointestinal system, with mild to moderate diarrhea and nausea. A low rate of discontinuation was observed in the studies. Telithromycin is an effective first-line treatment for mild to moderate respiratory infections in adults.

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.

Pharmacokinetics and Safety of the Ketolide Telithromycin in Patients with Renal Impairment

The pharmacokinetics and safety of the ketolide telithromycin were evaluated in two separate studies after single and repeat oral dosing in patients with varying degrees of renal impairment and in subjects with normal renal function. The single-dose study was an open-label, nonrandomized, parallel-group design in which all 40 patients received a single oral dose of telithromycin 800 mg. The repeat-dose study was an open-label study with a randomized, balanced, incomplete three-block treatment crossover design. In this study, each of the 36 patients received two of three telithromycin regimens (400, 600, or 800 mg once daily for 5 days), with a washout period of >/= 7 days between treatments. Telithromycin was well tolerated. Adverse events were generally mild in severity, and no serious drug-related adverse events were reported. Plasma exposure to telithromycin (C(max), AUC) showed a tendency to increase with increasing severity of renal impairment in both studies. In patients with severe renal impairment (CL(CR) < 30 mL/min) receiving telithromycin 800 mg in the repeat-dose study, C(max,ss) and AUC((0-24 h)ss) increased 1.5-fold (p < 0.05) to 2.0-fold (p = 0.0005), respectively, compared with healthy subjects. The percentage of dose excreted in urine and renal clearance (CL(R)) of telithromycin was found to decrease significantly with increasing severity of renal impairment in both studies, and CL(R) was found to be independent of telithromycin dose in the repeat-dose study. In conclusion, telithromycin dosage adjustment is not necessary in patients with mild to moderate renal impairment (CL(CR) >/= 30 mL/min). In patients with severe renal impairment (CL(CR) < 30 mL/min), dosage adjustment could be considered.

Spontaneous rupture of the spleen associated with Legionella pneumonia

Spontaneous rupture of the spleen associated with Legionella pneumonia is a rare and life-threatening complication; only three cases have been reported to date. The authors describe a case of a 47-year-old man who presented with pneumonia and abdominal pain. He underwent a splenectomy, and was successfully treated with clarithromycin and levofloxacin.

Benefit-risk assessment of telithromycin in the treatment of community-acquired pneumonia

The purpose of this review is to assess the benefits and risks associated with the use of the ketolide antibacterial telithromycin, currently licensed for the treatment of adults with mild to moderate community-acquired pneumonia (CAP). Telithromycin is active against both the major (Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis) and atypical/intracellular (Chlamydophila pneumoniae, Legionella pneumophila and Mycoplasma pneumoniae) CAP pathogens. It is associated with a low potential to select for resistance and has maintained its in vitro activity against isolates of respiratory pathogens in countries where it has been in clinical use for several years. In randomized clinical trials, telithromycin has demonstrated efficacy comparable to the established antibacterial classes (macrolides, fluoroquinolones and beta-lactams) in the treatment of CAP.The safety profile of telithromycin is broadly similar to that of other antibacterials used to treat CAP. The most common adverse events are gastrointestinal adverse effects and headache; these are generally mild to moderate in severity and reversible. Telithromycin appears to be well tolerated by adult patients in all age groups, including those with co-morbid conditions. In common with other antibacterials, telithromycin has the potential to affect the corrected QT interval; the concomitant use of cisapride or pimozide with telithromycin is contraindicated, while telithromycin should be avoided in patients receiving Class IA or Class III antiarrhythmic drugs. Visual disturbances (usually transient) have occurred in a small proportion of patients treated with telithromycin; it is recommended that activities such as driving are minimized during treatment. Telithromycin is contraindicated in patients with myasthenia gravis. Hepatic dysfunction may occur in some patients taking telithromycin; rare cases of acute hepatic failure and severe liver injury, including deaths, have been reported. As telithromycin is an inhibitor of the cytochrome P450 (CYP) 3A4 system, coadministration of telithromycin with drugs metabolized by this pathway may require dose adjustments (e.g. with benzodiazepines) or a temporary hiatus in the use of the coadministered drug (e.g. HMG-CoA reductase inhibitors) metabolized by CYP3A4. Telithromycin may potentiate the effects of oral anticoagulants; careful monitoring is recommended in patients receiving telithromycin and oral anticoagulants simultaneously.Although serious and sometimes fatal events have occurred in patients receiving telithromycin therapy, current data indicate that telithromycin offers an acceptable benefit risk ratio in the treatment of mild to moderate CAP.

Risk of Hepatotoxicity Associated with the Use of Telithromycin: A Signal Detection Using Data Mining Algorithms

Background:

With the exception of case reports, limited data are available regarding the risk of hepatotoxicity associated with the use of telithromycin.

Objective:

To detect the safety signal regarding the reporting of hepatotoxicity associated with the use of telithromycin using 4 commonly employed data mining algorithms (DMAs).

Methods:

Based on the Adverse Events Reporting System (AERS) database of the Food and Drug Administration, 4 DMAs, including the reporting odds ratio (ROR), the proportional reporting ratio (PRR), the information component (IC), and the Gamma Poisson Shrinker (GPS), were applied to examine the association between the reporting of hepatotoxicity and the use of telithromycin. The study period was from the first quarter of 2004 to the second quarter of 2006. The reporting of hepatotoxicity was identified using the preferred terms indexed in the Medical Dictionary for Regulatory Activities. The drug name was used to identify reports regarding the use of telithromycin.

Results:

A total of 226 reports describing hepatotoxicity associated with the use of telithromycin were recorded in the AERS. A safety problem of telithromycin associated with increased reporting of hepatotoxicity was clearly detected by 4 algorithms as early as 2005, signaling the problem in the first quarter by the ROR and the IC, in the second quarter by the PRR, and in the fourth quarter by the GPS.

Conclusions:

A safety signal was indicated by the 4 DMAs suggesting an association between the reporting of hepatotoxicity and the use of telithromycin. Given the wide use of telithromycin and serious consequences of hepatotoxicity, clinicians should be cautious when selecting telithromycin for treatment of an infection. In addition, further observational studies are required to evaluate the utility of signal detection systems for early recognition of serious, life-threatening, low-frequency drug-induced adverse events.

Severe Legionnaires' disease successfully treated using a combination of fluoroquinolone, erythromycin, corticosteroid, and sivelestat

The patient was a 67-year-old man with diabetes mellitus who had been to a hot spring spa a few days before his admission. The diagnosis of Legionella pneumonia was made using a urinary antigen assay. Intravenous pazufloxacin and oral clarithromycin were started. However, despite these treatments, he developed acute respiratory distress syndrome (ARDS). He was administered the combination of intravenous pazufloxacin and erythromycin, corticosteroid, and sivelestat for two weeks. Then he was successfully recovered. The outcome suggests that treatment with corticosteroid and sivelestat, in addition to a combination of appropriate anti-Legionella antibiotics, should be considered for patients with severe Legionella pneumonia with ARDS.

Telithromycin in lower respiratory tract infections

Telithromycin is a ketolide, a semisynthetic derivative of the 14-membered ring macrolide antibiotics, with an expanded spectrum of activity relative to macrolides. Its good tissue pharmacokinetic characteristics allows once-daily administration, and it has been successfully employed in lower respiratory tract infections. Recent data indicate that telithromycin may exert anti-inflammatory/immunomodulatory effects that may be of use in the treatment of both acute and chronic airway diseases. This review examines the role of telithromycin in lower respiratory tract infections, analyzing published data on exacerbations of chronic bronchitis, community-acquired pneumonia and asthma in adults. In addition, pharmacokinetic and pharmacodynamic properties of the drug are considered.

[Antibiotherapy for acute CAP in adults]

Community acquired pneumonia is one of the most frequent infections. With time, bacterial epidemiology and bacterial resistance evolve and new antibiotics become available. So an up-date on adequate antibiotic use is necessary. We reviewed the epidemiology of pneumonia and the evolution of bacterial resistance. We also collected data on new antibiotics which can be used for this infection such as levofloxacin, moxifloxacin, telithromycin, and pristinamycin. All these drugs are effective on bacteria involved in pneumonia. At this time, only few Streptococcus pneumoniae strains have developed resistance to these drugs. However, resistance to fluoroquinolones is not easily detected with common laboratory techniques. There is no effectiveness difference between the 2 new fluoroquinolones (levofloxacin, moxifloxacin) in clinical studies. However, in bacteriological and pharmacological studies, moxifloxacin seems to be more effective than levofloxacin (500 mg/day). For the treatment of pneumonia due to Legionella pneumophila, fluoroquinolones are now widely recommended. For Streptococcus pneumonia, amoxicillin remain the drug of choice, even for bacteria with a decreased susceptibility to penicillin. The importance of treating atypical pathogens remains to be documented.

Oral antibiotic therapy of serious systemic infections

Traditionally, antibiotics have been administered intravenously (IV) for serious systemic infections. As more potent oral antibiotics were introduced, and their pharmacokinetic aspects studied, orally administered antibiotics have been increasingly used for serious systemic infections. Antibiotics ideal for oral administration are those that have the appropriate spectrum, high degree of activity against the presumed or known pathogen, and have good bioavailability. Oral antibiotics with high bioavailability, that is > or = 90% absorbed, achieve serum/tissue concentrations comparable to IV administered antibiotics at the same dose. The popularity of "IV to PO switch therapy" is possible because of the availability of many potent oral antibiotics with high bioavailability. Initial IV therapy is appropriate in patients who are in shock/have impaired intestinal absorption, but after clinical defervescence, completion of therapy should be accomplished with oral antibiotics. As experience with "IV to PO switch therapy" has accumulated, confidence in oral antimicrobics for therapy of serious systemic infections has continued to increase. The trend in treating serious systemic infections entirely with oral antimicrobial therapy will continue, and is clearly the wave of the future.

[Clinically significant toxicity and tolerance of the main antibiotics used in lower respiratory tract infections]

The purpose of this article was not to review all reported adverse reactions of antibiotics used in the treatment of lower respiratory tract infections but rather to focus either on those which might have an impact on observance, efficacy, and resistance, or on rare but life-threatening adverse effects such as torsade de pointe. The latter are mostly predictable and prescribers should adhere to precautions and contraindications. For new antibiotics, the number of patients enrolled in phase I to III clinical trials is far to small to detect such rare adverse effects and large post registration tolerance surveys are mandatory. ss-lactams are well tolerated. The risk of anaphylactic reaction is magnified by patient reports and can be reduced by skin testing. Macrolides are well tolerated as well. The risk of cardiac toxicity should be reduced by assessing individual susceptibility and avoiding drug interactions. The tolerance to telithromycin, a new ketolide, is similar to that of macrolides. Serious toxic reactions such as convulsions, tendon rupture, torsade de pointe, and hypoglycemia are associated with the use of fluoroquinolones. Most of these adverse reactions can be often circumvented by avoiding exposure patients at risk. Quinupristin/dalfopristin can induce arthralgia and myalgia and the major adverse effects of linezolid are IMAO like reactions, reversible myelosuppression, and peripheral neuropathy. Most of the adverse antibiotic reactions are reported when precautions of use in susceptible patients are not taken into account. When they are, the safety/risk ratio is good.

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.

Intrapulmonary Concentrations of Telithromycin: Clinical Implications for Respiratory Tract Infections due to Streptococcus pneumoniae

BACKGROUND

Antimicrobial efficacy is dependent on the ability of the agent to reach the site of infection. To assess the bronchopulmonary drug disposition of a novel ketolide, telithromycin (TEL), the epithelial lining fluid (ELF) and alveolar macrophage (AM) concentrations were utilized as a surrogate marker for lung penetration.

METHODS

Adult subjects scheduled for diagnostic bronchoscopy received oral TEL 800 mg once daily for 5 days. Plasma and bronchoalveolar lavage (BAL) samples were collected 2, 8, 12, or 24 h after the last TEL dose. TEL concentrations in the ELF and AM were determined using a validated HPLC assay. ELF drug concentrations were calculated using the urea dilution method.

RESULTS

Seventeen subjects with a mean age 65 +/- 13 years and a mean weight of 81 +/- 25 kg completed this open-label study. The median (range) TEL concentrations in plasma and ELF, respectively, were 1.09 mg/l (1.00-4.81) and 3.91 mg/l (2.64-9.59) at 2 h (n = 6), 0.48 and 1.09 mg/l at 8 h (n = 1), 0.65 mg/l (0.18-1.55) and 1.81 mg/l (0.61-10.0) at 12 h (n = 5), and 0.11 mg/l (0.09-0.24) and 0.69 mg/l (0.15-1.58) at 24 h (n = 5). The median AM concentrations obtained from these subjects were 53.35 mg/l at 2 h, 32.55 mg/l at 8 h, 65.96 mg/l at 12 h, and 26.43 mg/l at 24 h. Overall TEL was well tolerated. No discontinuation was required due to an adverse event.

CONCLUSIONS

TEL displayed high intrapulmonary penetration with ELF concentrations exceeding that of plasma at all time points. AM intracellular concentrations were multiple times higher than in the ELF and plasma. These data support the clinical efficacy of TEL against intracellular and extracellular pathogens, particularly with Streptococcus pneumoniae having an MIC(90 )well below achievable concentrations at the site of infection.

Telithromycin: a novel agent for the treatment of community-acquired upper respiratory infections

The ketolides are a new subclass of macrolides, and telithromycin is the first of these agents to be approved. Modifications to the basic macrolide structure result in enhanced activity against penicillin- and erythromycin resistant respiratory pathogens. It is therefore an option in the treatment of mild to moderate community-acquired respiratory infections, such as pneumonia, acute exacerbations of chronic bronchitis, pharyngitis/tonsillitis, and sinusitis. Telithromycin also offers the advantages of once-daily dosing and a shorter course of therapy in certain infections. Comparative clinical trials, although limited and involving only a small number of resistant organisms, showed the equivalence of telithromycin to existing therapies, although telithromycin generally had a higher frequency of mild to moderate gastrointestinal adverse effects. Further clinical and safety data, especially in patients with resistant organisms, are needed.

Application of PCR for Mycoplasma pneumoniae detection in children with community-acquired pneumonia

Between April 2002 and March 2003, to detect Mycoplasma pneumoniae by polymerase chain reaction (PCR), a primer set designed for the 16S rRNA gene was used to examine clinical samples from 369 children with community-acquired pneumonia. Samples were collected from 12 Japanese institutions participating in a study group concerning acute respiratory infectious diseases. The sensitivity of primers--2 CFU per reaction tube, using M. pneumoniae M129, a standard strain--was calculated to represent 1.1 x 10(3) M. pneumoniae organisms adherent to the tip of the swab used to collect clinical samples. Results for PCR were obtained within 2.6 h. Cases identified by PCR, cultures, and serologic tests were 68 (18.4%), 53 (14.4%), and 76 (20.6%) respectively. Among 57 PCR-positive patients tested serologically, 56 showed a significant elevation or rise in antibody titer. PCR positivity was high among patients prescribed beta-lactam antibiotics (86.7%) or no antibiotic (87.0%) before PCR analysis, but was low among patients receiving macrolides, new quinolones, or tetracyclines (37.5%). We concluded that the PCR constructed by us had a high probability for confirming a diagnosis of M. pneumoniae pneumonia and for guiding antibiotic choice for patients not yet treated.

Efficacy of oral telithromycin in community-acquired pneumonia caused by resistant Streptococcus pneumoniae

The efficacy of oral telithromycin 800mg once daily for 7 days was evaluated in a multicentre, multinational study in patients with community-acquired pneumonia caused by Streptococcus pneumoniae resistant to penicillin and/or erythromycin. Per-protocol clinical and bacteriological outcomes were assessed 10-17 days post-therapy. Of the 129 patients with S. pneumoniae infection, 16 were infected with strains resistant to penicillin and/or erythromycin. Fifteen of these 16 patients (93.8%) were assessed as clinically and bacteriologically cured at the post-therapy visit.

Telithromycin: The first ketolide antimicrobial

BACKGROUND

Telithromycin is the first of the ketolide antibacterials to receive US Food and Drug Administration (FDA) approval for clinical use. It is approved for the treatment of community-acquired pneumonia (CAP), acute exacerbations of chronic bronchitis (AECB), and acute maxillary sinusitis (AMS) in adults.

OBJECTIVE

This article reviews the mechanism of action, in vitro antimicrobial activity, pharmacokinetics and pharmacodynamics, clinical efficacy, safety, and drug-interaction profile of telithromycin.

METHODS

Relevant studies were identified through a search of the English-language literature indexed on MEDLINE (1990-March 2005) using the terms telithromycin and HMR 3647, a review of the reference lists of identified articles, and a review of the briefing document prepared by the manufacturer of telithromycin for presentation to the FDA Anti-infective Drugs Advisory Committee. A search of abstracts from the Interscience Conference on Antimicrobial Agents and Chemotherapy (2001-2004) also was performed.

RESULTS

The results of in vitro susceptibility studies suggest that telithromycin provides coverage against the key respiratory pathogens, both typical and atypical. In addition, telithromycin may be useful against multidrug-resistant strains of Streptococcus pneumoniae and against Haemophilus influenzae, irrespective of beta-lactamase production. In randomized, double-blind, comparative trials (against amoxicillin, amoxicillin/clavulanate, cefuroxime axetil, clarithromycin, moxifloxacin, or trovafloxacin), telithromycin had comparable efficacy to its comparators in the empiric treatment of CAP (4 studies), AECB (3 studies), and AMS (3 studies). Telithromycin is dosed at 800 mg (two 400-mg tablets) QD in community-acquired respiratory tract infections (RTIs). No dose adjustment is required in the elderly, patients with mild to moderate renal insufficiency, or patients with hepatic insufficiency. The majority of adverse events associated with telithromycin were mild to moderate, with gastrointestinal effects (diarrhea, nausea, vomiting) being the most commonly reported, followed by headache and dizziness. Telithromycin has been associated with elevations in hepatic transaminases and prolongation of the electrocardiographic QTc interval, although the significance of these findings is not known. Telithromycin is also a strong inhibitor of and substrate for the cytochrome P450 (CYP) 3A4 isozyme. Therefore, it is important to monitor for potential drug interactions with medications that prolong the QTc interval or are metabolized by the CYP system.

CONCLUSIONS

Telithromycin appears to be a useful option for the empiric treatment of community-acquired RTIs in adults. It may be particularly useful in the outpatient setting in areas with high rates of penicillin- and macrolide-resistant S pneumoniae; it may also be an alternative agent for patients who are allergic to beta-lactams and live in areas with a high prevalence of multidrug-resistant S pneumoniae or for those who have failed to respond to beta-lactam- or macrolide-based therapy.

Efficacy of Telithromycin in Community-Acquired Pneumonia Caused by Pneumococci with Reduced Susceptibility to Penicillin and/or Erythromycin

BACKGROUND

The efficacy of oral telithromycin was assessed in patients with community-acquired pneumonia (CAP) caused by Streptococcus pneumoniae with reduced susceptibility to penicillin and/or erythromycin.

METHODS

Patients with CAP who had received telithromycin 800 mg once daily for 5 or 7-10 days (n = 2,289) in eight phase III clinical trials, or telithromycin 800 mg once daily for 7 days (n = 50) in a phase II study were included in this pooled analysis. Patients with S. pneumoniae as the cause of infection were identified, with particular focus on those infected with strains with reduced susceptibility to penicillin (intermediate, minimal inhibitory concentration (MIC) 0.12-1.0 mg/l; resistant, MIC >or=2.0 mg/l) and/or resistance to erythromycin (MIC >or=1.0 mg/l). Per-protocol clinical and bacteriological outcomes were assessed 7-14 days post-therapy in the phase III studies, and at 7-21 days post-therapy or at the end of therapy in the phase II study.

RESULTS

Of the 327 telithromycin-treated patients with S. pneumoniae infection, 61 (19%) were infected with strains with reduced susceptibility to penicillin and/or erythromycin. Clinical cure and bacterial eradication rates in these patients were 91.8% (56/61) and 93.4% (57/61), respectively. Corresponding clinical cure and bacterial eradication rates overall for all isolates of pneumococci were 94.5% (309/327) and 96.0% (314/327), respectively. All isolates with reduced susceptibility to penicillin and/or erythromycin were susceptible to telithromycin (MIC <or=1.0 mg/l).

CONCLUSION

These results indicate that telithromycin is an effective oral antibacterial for the treatment of CAP caused by pneumococci with reduced susceptibility to penicillin and/or erythromycin.

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.

Ketolides in the treatment of community-acquired respiratory tract infections: A review

BACKGROUND

The increasing prevalence of resistance to established antibiotics among key respiratory bacterial pathogens highlights a need for new antibacterial agents for the treatment of community-acquired respiratory tract infections (RTIs). Ketolides are a new class of antibiotics specifically developed for the treatment of RTIs.

OBJECTIVE

The aim of this review was to present the current status of treatment of RTIs with ketolides, focusing on telithromycin-the first ketolide to be approved by the US Food and Drug Administration for clinical use.

METHODS

TO GATHER EVIDENCE ON THE CURRENT STATUS OF KETOLIDES, A LITERATURE SEARCH WAS CONDUCTED USING MEDLINE (YEARS: 1990-2005; key terms: ketolides, telithromycin, and HMR3647).

RESULTS

Telithromycin shows strong in vitro activity against the major respiratorypathogens, including strains resistant to other antibiotics, as well as the atypical respiratory pathogens. The pharmacokinetic properties of telithromycin are compatible with once-daily dosing. Clinical trials have demonstrated that telithromycin 800 mg QD for 5 to 10 days is effective in the treatment of acute bacterial sinusitis, acute bacterial exacerbations of chronic bronchitis, and mild to moderate community-acquired pneumonia. Overall, telithromycin is well tolerated by patients. Drug-drug interactions are similar to those reported for macrolides.

CONCLUSION

Evidence to date indicates that telithromycin is an effective andwell-tolerated empiric treatment for community-acquired RTIs.

Comparative activity of quinolones, macrolides and ketolides against Legionella species using in vitro broth dilution and intracellular susceptibility testing

The comparative in vitro activity of quinolones (trovafloxacin, gemifloxacin, levofloxacin, ciprofloxacin, moxifloxacin and grepafloxacin), ketolides (ABT-773 and telithromycin) and macrolides (clarithromycin, azithromycin and erythromycin) were evaluated against Legionella pneumophila by broth dilution and an HL-60 intracellular model. The MIC90 of the quinolones, clarithromycin and ABT-773 were more than eight times lower than for erythromycin. Telithromycin, ABT-773 and azithromycin had significantly greater intracellular activity against L. pneumophila than erythromycin at 1xMIC and 8xMIC. The rank order of intracellular activity against L. pneumophila serogroup 1 was quinolones>ketolides>macrolides. Clinical trials to determine the clinical efficacy of ketolides for the treatment of Legionnaires' disease are warranted.

Telithromycin new product overview

Community-acquired respiratory tract infections (CARTIs), including community-acquired pneumonia, acute exacerbations of chronic bronchitis, and acute bacterial sinusitis, contribute substantially to health care costs in the United States. Although many prescriptions for antibiotics are written each year for the treatment of CARTIs, most are prescribed on an empiric basis. Concerns about the increasing prevalence of antimicrobial resistance and the changing pattern of pathogens isolated from subjects with CARTIs have raised questions about the empiric treatment paradigm. When choosing appropriate antimicrobial therapy for CARTIs, physicians must consider not only the spectrum of activity of antibiotics but also the potential risk of resistance. Telithromycin is the first member of the ketolide class, a new family of antimicrobials structurally related to the macrolides, to be approved by the US Food and Drug Administration for the treatment of CARTIs. The spectrum of activity of telithromycin includes common typical and atypical causative pathogens associated with community-acquired respiratory tract infections, including antibiotic-resistant strains of Streptococcus pneumoniae. Clinical trials have shown that telithromycin is as effective as traditionally used antimicrobial agents in the treatment of mild-to-moderate community-acquired pneumonia, acute exacerbations of chronic bronchitis, and acute bacterial sinusitis.

Macrolides and ketolides: azithromycin, clarithromycin, telithromycin

The advanced macrolides, azithromycin and clarithromycin, and the ketolide telithromycin are structural analogues of erythromycin. They have several distinct advantages when compared with erythromycin including enhanced spectrum of activity, more favorable pharmacokinetics and pharmacodynamics, once daily administration, and improved tolerability. This article reviews the pharmacokinetics, antimicrobial activity, clinical use, and adverse effects of these antimicrobial agents.

Mycoplasma pneumoniae and its role as a human pathogen

Mycoplasma pneumoniae is a unique bacterium that does not always receive the attention it merits considering the number of illnesses it causes and the degree of morbidity associated with it in both children and adults. Serious infections requiring hospitalization, while rare, occur in both adults and children and may involve multiple organ systems. The severity of disease appears to be related to the degree to which the host immune response reacts to the infection. Extrapulmonary complications involving all of the major organ systems can occur in association with M. pneumoniae infection as a result of direct invasion and/or autoimmune response. The extrapulmonary manifestations are sometimes of greater severity and clinical importance than the primary respiratory infection. Evidence for this organism's contributory role in chronic lung conditions such as asthma is accumulating. Effective management of M. pneumoniae infections can usually be achieved with macrolides, tetracyclines, or fluoroquinolones. As more is learned about the pathogenesis and immune response elicited by M. pneumoniae, improvement in methods for diagnosis and prevention of disease due to this organism may occur.

Hospitalization rates among patients with community-acquired pneumonia treated with telithromycin vs clarithromycin: results from two randomized, double-blind, clinical trials

AIMS

To compare hospitalization rates among patients with community-acquired pneumonia (CAP) treated with oral telithromycin and clarithromycin, based on pooled data from two randomized, double-blind, multinational clinical trials.

PATIENTS AND METHODS

Adult patients with CAP eligible for oral therapy (Study 1, n = 448; Study 2, n = 575) received telithromycin 800 mg once daily for 10 (Study 1, 2-arms), 5 or 7 (Study 2, 3-arms) days, or clarithromycin 500 mg twice daily for 10 days. Frequency of CAP-related hospitalizations, physician visits/tests/procedures, and additional respiratory tract infection-related antibacterial use, as well as CAP-related length of hospital stay and hospitalization costs, were compared by treatment group (intent to treat populations) up until the late post-therapy visit (Days 31-36). Study investigators blinded to treatment regimen assessed whether hospital admissions were CAP related.

RESULTS

Despite equivalent clinical efficacy for telithromycin vs clarithromycin in the clinically evaluable per-protocol populations (n = 784) (88.8% [428/482] vs 90.1% [272/302]--difference: -1.3%; 95% CI: -6.0, 3.4), telithromycin treatment for 5, 7, or 10 days was associated with significantly fewer CAP-related hospitalizations (p = 0.023) and CAP-related hospital days (p = 0.025) vs clarithromycin (reduction of 2.3 hospitalizations and 23.4 hospital days per 100 patients). Accordingly, estimated CAP-related hospitalization costs were significantly lower (p = 0.025) for telithromycin recipients (30,231 US dollars less per 100 patients). CAP-related hospitalizations, duration of hospital stay, and hospitalization costs for 7- to 10-day telithromycin--the approved dosing regimen for CAP--were significantly lower (p = 0.023, 0.025, and 0.025, respectively) than for clarithromycin.

CONCLUSIONS

Data from this study indicate that telithromycin 800 mg once daily for 5, 7, or 10 days provides an effective therapy for patients with CAP, and may be associated with fewer CAP-related hospitalizations and hospital days than clarithromycin 500 mg twice daily for 10 days. Treatment with telithromycin could, therefore, potentially translate into cost savings in the management of CAP.

Clinical and bacteriological efficacy of the ketolide telithromycin against isolates of key respiratory pathogens: a pooled analysis of phase III studies

A pooled analysis of data from 13 phase III studies of telithromycin in the treatment of community-acquired pneumonia, acute exacerbations of chronic bronchitis, acute sinusitis or group A beta-haemolytic streptococcal pharyngitis and tonsillitis was undertaken. Causative key respiratory tract pathogens (Streptococcus pneumoniae, Haemophilus influenzae, Moraxella catarrhalis, Staphylococcus aureus and Streptococcus pyogenes) were isolated at entry to the studies from cultures of relevant respiratory samples and tested for their susceptibility to telithromycin, penicillin and macrolides (erythromycin A). The combined clinical and bacteriological efficacy of telithromycin at the post-therapy, test-of-cure visit (days 17-24) was assessed in patients from whom a microbiologically evaluable pathogen was isolated at entry. More than 98% of key respiratory pathogens isolated, including penicillin G- and macrolide (erythromycin A)-resistant strains of S. pneumoniae, demonstrated full or intermediate susceptibility to telithromycin in vitro at the breakpoints of < or = 1.0 mg/L (susceptible) and 2.0 mg/L (intermediate) used for the purpose of evaluating the susceptibility of isolates recovered during the clinical trials. Treatment with telithromycin 800 mg once-daily for 5, 7 or 7-10 days resulted in high rates of clinical cure (88.5%) and a satisfactory bacteriological outcome (88.9%), similar to the figures seen with comparator antibacterial agents. Clinical cure and eradication rates were good for all key respiratory pathogens, including penicillin G- and macrolide (erythromycin A)-resistant S. pneumoniae. The results suggest that telithromycin will provide effective empirical therapy for community-acquired upper and lower respiratory tract infections.

Telithromycin

Telithromycin, the first member of the ketolide antibacterials, has good activity against community-acquired respiratory pathogens, including multiple-drug-resistant strains of Streptococcus pneumoniae. Telithromycin 800 mg once daily has been US FDA approved for the treatment of acute bacterial sinusitis (ABS; treatment duration 5 days), acute bacterial exacerbations of chronic bronchitis (AECB; 5 days) and mild-to-moderate community-acquired pneumonia (CAP; 7-10 days). In patients with CAP, telithromycin was as effective as amoxicillin 1000 mg three times daily for 10 days, clarithromycin 500 mg twice daily for 10 days or trovafloxacin 200 mg once daily for 7-10 days. In patients with AECB, telithromycin was as effective as a 10-day regimen of amoxicillin/clavulanic acid 500/125 mg three times daily, cefuroxime axetil 500 mg twice daily or clarithromycin 500 mg twice daily. In patients with ABS, telithromycin was as effective as a 10-day course of amoxicillin/clavulanic acid 500/125 mg three times daily or cefuroxime axetil 250 mg twice daily. Telithromycin was generally well tolerated and most adverse events were of mild-to-moderate severity and transitory. The most common adverse events with telithromycin were diarrhoea and nausea (10.8% and 7.9% of 2702 patients in clinical trials); these events occurred in 8.6% and 4.6% of 2139 comparator-treated patients.