Short-course antimicrobial therapy of respiratory tract infections

Future Trends in Antimicrobial Chemotherapy: Expert Opinion on the 43rdICAAC

The current document bestows an expert synopsis of key new information presented at the 43rd Interscience Conference on Antimicrobial Agents and Chemotherapy (ICAAC) meeting in 2003. Data is presented on the socio-political aspects of and policies on antimicrobial prescribing, novel mechanisms of resistance in Streptococcus pneumoniae, and current epidemiological trends in global resistance. Novel information on new (and existing) antimicrobial agents--new penicillins, cephalosporins, monobactams and oxipenem inhibitors, ketolides, glycopeptides, fluoroquinolones (and hybrids), peptides, daptomycin, aminomethylcyclines, glycylcyclines, and newer formulations of agents such as amoxycillin-clavulanate--provides renewed hope that resistant pathogens can be controlled through use of more potent agents. Improved strategies for the use of existing antimicrobial agents, such as the use of high-dose regimens, short-course therapy, also may delay or reduce the development of resistance and preserve the value of our antibiotic armamentarium.

A pilot study of high-dose short duration daptomycin for the treatment of patients with complicated skin and skin structure infections caused by gram-positive bacteria

BACKGROUND

Methicillin-susceptible and -resistant (MRSA) Staphylococcus aureus are significant causes of complicated skin and skin structure infections (cSSSI). The bactericidal antibiotic daptomycin is approved for gram-positive cSSSI at 4 mg/kg/day for 7-14 days, but the optimal dose level and duration of therapy have not been firmly established. This pilot study evaluated the efficacy and safety of daptomycin at 10 mg/kg every 24 h for 4 days [high-dose short duration (HDSD) regimen] vs. standard of care therapy with vancomycin or semi-synthetic penicillin for the treatment of cSSSI.

METHODS

This was a semi-single blind, randomised, multicentre, comparative trial. The primary efficacy end-point was the clinical response 7-14 days posttherapy.

RESULTS

One hundred patients were randomised; 48 in each arm were treated. The treatment groups were well balanced with respect to demographics, comorbidities and the type of infection (75% because of MRSA). Overall, clinical success rates were 75.0% (36/48) for daptomycin and 87.5% (42/48) for comparator (95% confidence interval for the difference: -27.9, 2.9). The median duration of comparator therapy was 8 days. Two comparator patients and no daptomycin patients experienced treatment-related serious adverse events requiring hospitalisation.

CONCLUSION

We found that the HDSD regimen had a safety profile similar to that seen in previous studies. Although the differences were not statistically significant, clinical success rates for comparator were higher than for daptomycin. In post hoc analyses HDSD daptomycin performed better in some subgroups (e.g. outpatients) than in others (e.g. certain MRSA infections). These observations require confirmation in larger trials.

Role for 5-day, once-daily extended-release clarithromycin in acute bacterial exacerbation of chronic bronchitis

BACKGROUND

Clarithromycin is commonly dosed for 7 or more days in patients with acute bacterial exacerbation of chronic bronchitis (ABECB). Studies with other antibiotics have shown equivalent efficacy, reduced/similar frequency of adverse events, improved adherence and patient satisfaction, and lower treatment costs with a shorter treatment course.

PATIENTS AND METHODS

The study population was derived from two multicenter, randomized, double-blind (North America)/single-blind (France) comparative trials in which outpatients at least 35 years old with a presumptive diagnosis of obstructive ABECB were randomized to receive clarithromycin extended-release (ER) 1000 mg once daily for 5 days or a comparator agent--clarithromycin immediate-release (IR) 500 mg twice daily for 7 days (in North America) or telithromycin 800 mg once daily for 5 days (in France).

RESULTS

A total of 818 patients were randomized (411 to clarithromycin ER and 407 to a comparator agent). The clinical cure rate in clinically evaluable patients at the follow-up visit was 90% each for the clarithromycin ER group (318/353) and the comparator group (318/355). The patient bacteriological cure rate and the overall target pathogen eradication rate in clinically and bacteriologically evaluable patients were each 92% for the clarithromycin ER group (155/168 and 189/205, respectively) and 93% for the comparator group (147/158 and 183/197, respectively) at the follow-up visit. The study drugs were generally well tolerated, with < 2% of patients discontinuing their treatment prematurely due to a drug-related adverse event. The incidence of drug-related adverse events was 18% (73/411) in the clarithromycin ER group and 24% (97/407) in the comparator group. Clarithromycin ER-treated patients reported statistically significantly fewer episodes of abdominal pain than did patients treated with a comparator agent (0.2% vs. 1.7%, respectively; p = 0.037). This combined analysis is limited by differing blinding methods, comparator agents, and their duration of administration. Furthermore, many patients were excluded from the clinically and bacteriologically evaluable group due to lack of a pretreatment target pathogen.

CONCLUSION

A once daily, 5-day clarithromycin ER regimen appears to be a suitable choice for treating patients with ABECB.

Principles of Antimicrobial Therapy

The most compelling reason for practicing judicious antimicrobial use is to facilitate therapeutic success. The definition of therapeutic success has changed in recent years, however; not only does success include eradication of infection, but it must now include avoidance of resistance. If the goal of antimicrobial therapy is to achieve sufficient concentrations at the site of infection such that the infecting organism is killed, therapy should be successful.

A comparison of 5 days of therapy with cefdinir or azithromycin in children with acute otitis media: a multicenter, prospective, single-blind study

BACKGROUND

Short-course therapy for acute otitis media (AOM) improves adherence and may reduce secondary bacterial resistance.

METHODS

In this multicenter, prospective, investigator-blinded study, patients between the ages of 6 months and 6 years with a clinical diagnosis of AOM were randomized to receive cefdinir oral suspension 7 mg/kg q12h for 5 days or azithromycin oral suspension 10 mg/kg once daily on day 1 and 5 mg/kg once daily on days 2 through 5. Clinical response was assessed at the end-of-therapy (EOT) visit (days 7-9) and the follow-up visit (days 20-25).

RESULTS

Three hundred fifty-seven patients were enrolled in the study. The treatment groups were similar at baseline with respect to demographic characteristics (mean [SD] age, 3.0 [1.7] years; 55% male), incidence of bilateral AOM (45%), and presenting signs and symptoms. The majority of evaluable children (77%) had previously received conjugated heptavalent pneumococcal vaccine (PCV7) against Streptococcus pneumoniae. At the EOT visit, clinical cure rates were comparable for cefdinir and azithromycin (87% [151/174] and 85% [149/176], respectively; 95% CI, -5.5 to 9.8). In addition, clinical cure rates at the EOT visit in the children who had been vaccinated with PCV7 were comparable between cefdinir and azithromycin (86% vs 83%; 95% CI, -6.5 to 11.8). No significant difference in clinical cure rates was observed at the follow-up visit (76% and 86%; 95% CI, -18.9 to 0.0). Parental satisfaction was similar between treatment groups with regard to ease of use, taste, compliance, health care resource utilization, and missed days of work and day-care. Both antibiotics were well tolerated; diarrhea and abnormal stools were the most common antibiotic-related adverse events (< or = 7% each).

CONCLUSIONS

Short courses (5 days) of therapy with cefdinir or azithromycin were comparable in these children with AOM based on clinical end points, parental preferences, and health care utilization.

Enhanced efficacy of single-dose versus multi-dose azithromycin regimens in preclinical infection models

OBJECTIVES

As a result of the prolonged half-life and unique pharmacokinetic and pharmacodynamic (PK-PD) characteristics of azithromycin, shorter dosing regimens are being evaluated for the treatment of community-acquired infections. To provide further support for a shorter dosing regimen, the efficacy of azithromycin was determined in preclinical infection models comparing single- versus multi-dose regimens.

METHODS

The efficacy of single versus multi-dose regimens of azithromycin was compared in mouse pneumonia, acute peritonitis, and neutropenic thigh infection models and in a gerbil model of Haemophilus influenzae acute otitis media. Azithromycin was administered as a single oral dose on the first treatment day, or as two divided doses over 2 treatment days, or as three divided doses over 3 treatment days. The pharmacokinetics of azithromycin was profiled following single and multi-dose regimens with the single dose data fit to an Emax model to characterize the PK-PD of azithromycin.

RESULTS

In the mouse efficacy models, administration of single-dose azithromycin produced superior rates of survival and bacterial clearance compared with the same total dose divided over 2 or 3 days. In the gerbil model, a single dose sterilized the middle ear and more rapidly cleared H. influenzae. The pharmacokinetic evaluation confirmed similar total exposure (AUC) in serum and pulmonary tissue for the three regimens. Correlation of PK-PD parameters and antimicrobial efficacy confirmed a concentration-dependent and dosing-independent relationship for azithromycin.

CONCLUSIONS

These data are consistent with data reported from clinical studies and indicate that a single-dose regimen would be at least as effective as the same dose administered over several days.

Prospective observational study of patient-reported outcomes for azithromycin versus usual care in the treatment of bacterial acute exacerbation of chronic bronchitis

BACKGROUND

The 3-day course of azithromycin (AZM) 500 mg/d was introduced to the US market in June 2002.

OBJECTIVE

The objective of this study was to evaluate changes in health-related quality of life (HRQOL) as measured by the St. George's Respiratory Questionnaire (SGRQ) over a 1-month period in patients receiving a 3-day course of AZM for bacterial acute exacerbation of chronic bronchitis (AECB).

METHODS

This was a prospective, multicenter, observational study evaluating outpatient adults with AECB who received either 3 days of AZM 500 mg/d or 5- to 14-day courses of other antibiotics (usual care [UC]) as directed by the clinician. Patients completed 2 HRQOL instruments-the SGRQ and Medical Outcomes Study 36-Item Short-Form Health Survey (SF-36)-at baseline, day 14, and end of study (EOS) at days 24 to 28. In addition, patients kept a diary for the first 14 days after initiating antibiotic therapy.

RESULTS

One hundred twenty-eight patients (57 AZM, 71 UC) were clinically evaluable. There were no significant differences between treatment groups in clinical presentation or baseline demographics, with the exception of a higher percentage of patients with diabetes mellitus in the UC group compared with the AZM group (16.9% vs 3.5%; P = 0.02). Both groups reported similar improvements in signs and symptoms, absenteeism, concomitant respiratory medication use, resource utilization, compliance, and treatment satisfaction as reported in the patient diary. The AZM group reported statistically significant improvement (simple contrasts for end of study vs baseline) in SGRQ measures (total score, P < 0.001; symptoms, P = 0.031; activity, P < 0.001; impacts, P < 0.001) and the SF-36 mental and physical summary components, compared with baseline (both, P < 0.001). Similarly, the UC group reported significant improvement in all SGRQ measures and in the SF-36 physical component score (P < 0.01), but not in the SF-36 mental component score, compared with baseline. At EOS, 80.0% of AZM patients and 59.0% of UC patients had a > or =4-point improvement on the SGRQ total score; however, this difference was not statistically significant in the multivariate analysis. In addition, 89.5% of AZM patients and 89.9% of UC patients were satisfied or very satisfied with their treatment (P = NS). Resource utilization was similar between the groups.

CONCLUSIONS

In this observational study, patients with AECB treated with a 3-day course of AZM experienced significant improvements in HRQOL as measured by a change of > or =4 points on the SGRQ and SF-36 physical and mental component scores versus baseline.

Treatment options for acute sinusitis in children

Much controversy exists regarding the best diagnostic method for acute sinusitis, the efficacy of antibiotics, the best choice of antibiotics, the most appropriate duration of therapy, and the efficacy of ancillary measures and nasal corticosteroids. The therapeutic goal is to identify those children who are more likely to have bacterial sinusitis and unlikely to resolve spontaneously, who may require treatment with antibiotics. The inaccuracy of clinical signs and symptoms complicates further the management of these children. Acute sinusitis is expected to resolve spontaneously in most cases, including many cases of bacterial sinusitis. Antibiotics are needed only for a minority of non-self-resolving infections. Based on current resistance considerations, approximately 80% of bacterial infections are expected to respond to standard doses of amoxicillin. High-dose amoxicillin, amoxicillin/clavulanate, or other b-lactam antibiotics should be considered for children at high risk for carrying resistant organisms. Evidence for the effectiveness of ancillary measures is limited.

Clinical implications of 750 mg, 5-day levofloxacin for the treatment of community-acquired pneumonia

OBJECTIVE

To evaluate the time to symptom resolution and i.v.-to-p.o. transition in community-acquired pneumonia (CAP) patients treated with 750 mg or 500 mg levofloxacin.

RESEARCH DESIGN

A retrospective, subset analysis of a multicenter, randomized, double-blind, controlled trial comparing 750 mg levofloxacin for 5 days to 500 mg levofloxacin for 10 days for the treatment of CAP.

PATIENTS AND METHODS

A total of 528 CAP patients were included. Baseline symptoms were re-evaluated on Day 3 of therapy, and time to i.v.-to-p.o. transition was recorded for inpatients.

RESULTS

For the overall population, 67.4% of patients receiving 750 mg levofloxacin had resolution of fever by Day 3 of therapy, compared to 54.6% of 500 mg treated patients (P = 0.006). Patients who started on 750 mg levofloxacin i.v. (N = 108) transitioned to p.o. in an average of 2.68 days while those starting on 500 mg i.v. (N = 124) transitioned in 2.95 days (P = 0.144). The median time for i.v.-to-p.o. switch was 2.35 days and 2.75 days for patients receiving 750 mg and 500 mg levofloxacin, respectively (P = 0.098, log rank test). By Day 3 of therapy, 68% of patients receiving the 750 mg dose had transitioned from i.v. to p.o. levofloxacin, compared with 61% of the 500 mg group (P = 0.280). The safety profiles were comparable for the two regimens.

CONCLUSIONS

The 750 mg levofloxacin dose resulted in a greater proportion of patients with resolution of CAP symptoms by Day 3 when compared with 500 mg therapy. Consequently, the 750 mg regimen trended toward more rapid transition to p.o., potentially resulting in lower overall drug costs. Time to switch from i.v. to p.o. was determined by the investigators' discretion rather than a set protocol. Additionally, length of stay data was not collected in this study, which can significantly impact overall healthcare costs. Further research is required to fully understand the economic impact of the 750 mg, 5-day levofloxacin regimen.