A comparative study of meropenem and ceftazidime in the treatment of patients hospitalized with community-acquired pneumonia

The risk of seizures among the carbapenems: a meta-analysis

OBJECTIVES

A consensus exists among clinicians that imipenem/cilastatin is the most epileptogenic carbapenem, despite inconsistencies in the literature.

METHODS

We conducted a meta-analysis of all randomized controlled trials comparing carbapenems with each other or with non-carbapenem antibiotics to assess the risk of seizures for imipenem, meropenem, ertapenem and doripenem.

RESULTS

In the risk difference (RD) analysis, there were increased patients with seizure (2 per 1000 persons, 95% CI 0.001, 0.004) among recipients of carbapenems versus non-carbapenem antibiotics. This difference was largely attributed to imipenem as its use was associated with an additional 4 patients per 1000 with seizure (95% CI 0.002, 0.007) compared with non-carbapenem antibiotics, whereas none of the other carbapenems was associated with increased seizure. Similarly, in the pooled OR analysis, carbapenems were associated with a significant increase in the risk of seizures relative to non-carbapenem comparator antibiotics (OR 1.87, 95% CI 1.35, 2.59). The ORs for risk of seizures from imipenem, meropenem, ertapenem and doripenem compared with other antibiotics were 3.50 (95% CI 2.23, 5.49), 1.04 (95% CI 0.61, 1.77), 1.32 (95% CI 0.22, 7.74) and 0.44 (95% CI 0.13, 1.53), respectively. In studies directly comparing imipenem and meropenem, there was no difference in epileptogenicity in either RD or pooled OR analyses.

CONCLUSIONS

The absolute risk of seizures with carbapenems was low, albeit higher than with non-carbapenem antibiotics. Although imipenem was more epileptogenic than non-carbapenem antibiotics, there was no statistically significant difference in the imipenem versus meropenem head-to-head comparison.

Efficacy of meropenem as monotherapy in the treatment of ventilator-associated pneumonia

We performed a prospective, open label, randomized study in intensive care unit patients with ventilator-associated pneumonia (VAP) to determine the efficacy and safety of empiric intravenous (i.v.) meropenem monotherapy compared with the combination of ceftazidime plus amikacin. A total of 140 patients receiving mechanical ventilation and diagnosed with pneumonia were included in the study. Patients were randomized to receive either 1 g meropenem i.v. every 8 hours or 2 g ceftazidime i.v. every 8 hours plus 15 mg/kg amikacin daily, administered to patients with normal renal function as two daily doses. Satisfactory clinical responses (cure or improvement) were achieved at the end of treatment in 68.1% of meropenem-treated patients and 54.9% in the ceftazidime/amikacin-treated group (relative risk 1.25; 95% confidence interval >1.00, 1.55). When non-evaluable patients were excluded from the analysis, the satisfactory clinical response was 82.5% and 66.1% for the meropenem and ceftazidime/amikacin patients, respectively (p = 0.044). Logistic regression demonstrated that treatment with meropenem and both the basic traumatic and medical pathologies were significantly associated with a satisfactory response. Adverse events judged to be possibly or probably related to treatment were reported by seven (10.1%) patients in the meropenem group and by eight patients (11.3%) in the ceftazidime/amikacin group. The results of this study confirm that monotherapy with meropenem is well tolerated and provides superior efficacy to the conventional combination of ceftazidime and amikacin in combating VAP.

Meropenem: clinical response in relation to in vitro susceptibility

OBJECTIVE

To collate the clinical response and pathogen eradication rates for meropenem monotherapy with in vitro susceptibility of the causative pathogens.

METHODS

Data were compiled from 17 randomized clinical studies that compared meropenem monotherapy with standard treatment options, often combinations. A total of 4906 pathogens from lower respiratory tract, intra-abdominal, obstetric/gynecological, skin/soft tissue, meningitis, or pediatric infections were assessed. Of these, 3713 pathogens (1963 meropenem, 1750 comparators) were evaluable.

RESULTS

The overall rates of satisfactory clinical response (cure or improvement) and pathogen eradication (eradication or presumed eradication) at the end of therapy were similar with meropenem (93% for both responses) and the comparators (92%), as were the rates in each infection type. For each pathogen, the clinical response and eradication rates with meropenem were similar across the minimum inhibitory concentration (MIC) range of < or = 0.25 to 4 mg/L. Overall, a satisfactory clinical response occurred in 93% (1580 of 1708) of infections caused by nonfastidious pathogens with MICs < or = 4 mg/L and in 84% (16 of 19) of those with an MIC of 8 mg/L. Pathogen eradication rates were similar (93 and 79%, respectively). A similar profile was observed for fastidious pathogens. The high rates of satisfactory clinical response and pathogen eradication produced by meropenem in each type of infection were generally independent of the causative pathogen, whether Gram-positive or -negative aerobe or anaerobe or when occurring as mono- or polymicrobial infections.

CONCLUSIONS

The attractive in vitro profile of meropenem translates into good clinical efficacy. The National Committee for Clinical Laboratory Standards has now defined meropenem MIC breakpoints for nonfastidious aerobes or anaerobes as < or = 4 (susceptible), 8 (intermediate) and > or = 16 mg/L (resistant), respectively. The susceptibility breakpoint for Streptococcus spp. (excluding Streptococcus pneumoniae) is < or = 0.5 mg/L and, since meropenem is indicated for the treatment of meningitis, the susceptibility breakpoint for S. pneumoniae and Haemophilus influenzae is < or = 0.25 and < or = 0.5 mg/L, respectively. Meropenem monotherapy is therefore a valid option for the initial empirical treatment of a range of serious infections caused by single or multiple bacterial pathogens.

Meropenem in elderly and renally impaired patients

The safety profile of meropenem in the elderly (aged > 65 years, n=843) and/or renally impaired (creatinine clearance < 51 ml/min, n=436) was assessed by evaluating data from 26 phase III studies which compared the use of meropenem (0.5 or 1.0 g, i.v. every 8 h) with other antimicrobial agents in patients with bacterial infections. The overall pattern and frequency of adverse events following meropenem therapy in the elderly and/or renally impaired were similar to those in younger and/or non-renally impaired cohorts and to imipenem/cilastatin and injectable third generation cephalosporins. Both dosages of meropenem (0.5 and 1.0 g, i.v. every 8 h) were generally well tolerated. There was no clinically significant mean change in indicators of renal flux between baseline and the end of treatment in any patient sub-group. Importantly, meropenem-related seizures were rare (0.1%), even in patients with renal impairment. In summary, meropenem has an excellent safety profile and is therefore suitable for use in elderly and/or renally impaired patients.

Pneumonia: the impact of risk factors on the outcome of treatment with meropenem and ceftazidime

This analysis comprises data pooled from two clinical trials of meropenem (0.5 g 8-hourly) versus ceftazidime (1 g 8-hourly) in hospitalized patients with community-acquired pneumonia. The clinical and bacteriological responses to treatment were assessed in relation to a range of risk factors previously linked to a poor clinical outcome. 393 patients (198 meropenem, 195 ceftazidime) were clinically evaluable while 230 (113 meropenem, 117 ceftazidime) were bacteriologically evaluable. Meropenem was highly effective, independent of associated risk factors, producing overall satisfactory clinical and bacteriological response rates at the end of therapy of 91.4% and 94.7%, respectively, similar to those produced by ceftazidime (90.3% and 92.3%, respectively). Clinical and bacteriological treatment outcome were similar in patients with up to three of the following key risk factors: age > or =65 years, male gender, serum urea >7 mmol/L, serum albumin <35 g/L and difficult-to-treat pathogens. Meropenem also achieved high clinical (85.7%) and bacteriological (89.3%) success rates in patients requiring ventilation, as did ceftazidime (81.6% and 87.1%, respectively). Both agents were highly effective against both Gram-negative and Gram-positive causative pathogens, including those organisms normally considered difficult to treat and typical of nosocomial pneumonia (e.g. Enterobacteriaceae, Staphylococcus aureus, Pseudomonas aeruginosa). Thus, meropenem and ceftazidime were highly effective in patients hospitalized with community-acquired pneumonia, irrespective of a number of concurrent risk factors (including those regarded as key risk factors). Furthermore, the analysis points to a role for meropenem 0.5 g 8-hourly in the treatment of nosocomial pneumonias that do not require intensive care unit admission and/or mechanical ventilation. Overall, this novel analysis of trial data suggests that incorporation of key risk factor endpoints into the initial design of pneumonia studies may prove to be a useful approach in defining appropriate antibiotic treatment for specific patient groups.