To review clinical trials comparing carbapenem monotherapy with other antibiotics used in combination for patients with intra-abdominal infections.

MEDLINE was searched from 1985 to 1996, limited to English language papers; search terms were provided. Reference lists of retrieved papers were examined.

Study designs of evaluations included in the review

Randomised controlled trials (RCTs) were included.

Specific interventions included in the review

Carbapenem monotherapy (imipenem/cilastatin or meropenem). Control groups received other antibiotics in combination, including aminoglycoside with clindamycin, third-generation cephalosporin with metronidazole, quinolone with metronidazole and piperacillin with tazobactam.

Participants included in the review

Patients with intra-abdominal infections. Trials recruiting only patients with appendicitis were excluded. Patients with renal insufficiency, neutropenia, history of anaphylactoid reactions to study drugs, central nervous system disease and pregnancy were excluded.

Outcomes assessed in the review

A successful outcome was defined as cure or improvement of clinical signs and symptoms of infection, with no evidence of infection and no relapse at follow-up. Failure was defined as either persistent or recurrent signs of intra-abdominal infection that required additional antibiotics or death attributable to the intra-abdominal infection.

How were decisions on the relevance of primary studies made?

Abstracts of trials were screened. No additional information was provided regarding the process by which decisions were made.

The authors did not state that they assessed validity.

For each study, differences in response rates and response ratios were calculated. In addition, the chi-square statistic and p-value were recalculated and compared with those reported by the original authors. No additional information was provided regarding the process of data extraction.

How were the studies combined?

Summary response ratios were calculated using the Mantel-Haenszel method. In addition, the overall difference in response rates was calculated by summing the event rates across studies.

How were differences between studies investigated?

Trials evaluating different types of carbapenem monotherapy (imipenem/cilastatin and meropenem) were analysed separately.

Ten RCTs (n=1,227) were included.

Statistical re-analysis of reported data from individual studies showed that, out of the 10 included trials, 6 reported carbapenem monotherapy to be equivalent to other antibiotic regimes, 2 trials reported superior outcomes with carbapenem monotherapy and 2 had outcomes favouring other antibiotic regimes. Some discrepancies were noted between values reported by authors of primary studies and those calculated by the authors of the review.

There were no statistically-significant differences in response rates between carbapenem monotherapy and combinations of other antibiotics (-1.6%95% CI:-5.7, 2.5%). No significant differences were found when trials of imipenem/cilastatin (n=8) and meropenem (n=2) were analysed separately.

There were no statistically-significant differences in response ratios between carbapenem monotherapy and combinations of antibiotics (0.99%95% CI:0.90, 1.09%). Again, no significant differences were found when trials of imipenem/cilastatin and meropenem were analysed separately.

Carbapenem monotherapy is as effective as combinations of other antimicrobials for the treatment of intra-abdominal infections.

The research question and inclusion criteria for primary studies are clearly reported, and details of trials are presented in tables. The pooling methods used are appropriate. The search strategy is reported, but the limitation to one database and English language only may mean that relevant material has been missed. There is no mention of an assessment of the methodological quality of included trials.

This is a critical abstract of a systematic review that meets the criteria for inclusion on DARE. Each critical abstract contains a brief summary of the review methods, results and conclusions followed by a detailed critical assessment on the reliability of the review and the conclusions drawn.