Background Ertapenem (Invanz) was the third carbapenem approved by European Medicines Agency. It is mainly used for the treatment of polymicrobial infections. Nonetheless, while ertapenem enjoyed market exclusivity period of time, generic alternatives are now marketed, so Invanz is the most expensive option. Moreover, there is no evidence to show that this brand is better; non-inferiority studies are required for licensing approval.

Purpose The aim of this study was to evaluate what The authors would have saved if The authors had used alternative brands of ertapenem, shown to be non-inferior by the scientific literature and antibiograms. No data have been published since the alternative generic drugs were commercialised.

Materials and methods Observational, retrospective study, carried out in a General Hospital. All patients treated with at least one dose of ertapenem were evaluated from January to June 2011. Information was obtained by reviewing clinical histories. The clinical justification for each case, antibiogram and duration of treatment were recorded. Afterwards, the costs of ertapenem treatment and the cheaper non-inferior alternatives were estimated according with the Antimicrobial Treatment Hospital Guidelines.

Results 90 patients were identified: 51 intra-abdominal infections, 9 diabetic foot infections, 9 prophylaxis of surgical site infections, 7 urinary tract infections, 6 cases of community-acquired pneumonia, 8 other infectious. 87 patients (96.66%) treated with Invanz could have been treated with other antimicrobials. 79 patients (90.80%) could have been treated directly with a non-inferior generic drug. Over six months, the money spent on ertapenem could have been reduced by 84.72%.

22,265€ were spent because of Invanz treatments. The alternative non-inferior generics would have cost 3,400.13€: 2,662.3€ piperacillin/tazobactam +215.73€ amoxicillin/clavulanic +309.12 imipenem +35.1€ cefoxitin + 177.88€ other minority cases according to the antibiogram.

37,730€ could be saved each year if a non-inferior generic were selected instead of ertapenem.

Conclusions Instead of using ertapenem, other non-inferior generic alternatives could obtain significant savings.