Comparative clinical trial of imipenem-cilastatin (N-formimidoyl-thienamcyin-dehydropeptidase inhibitor) and cefazolin

One hundred and eighty-six patients were randomized to receive either imipenemcilastatin (94 patients) or cefazolin (92 patients). Imipenem-cilastatin (250 mg 6 hourly iv) or cefazolin (1000 mg 6 hourly iv) were given for 5 to 14 days. An assessment of efficacy could be made in 141 patients, 72 of whom received imipenem-cilastatin and 69 of whom received cefazolin. Reasons for exclusion included failure to isolate a causative organism (20 patients), less than 5 days of treatment (16 patients), inadequate follow up or culture (5 patients), concomitant administration of another antibiotic (1 patient), and resistance to the study drug (3 patients, all of whom were in the cefazolin group). No isolates resistant to imipenem were found. Sites of infection included skin and soft tissue (91 patients), lower respiratory tract (21 patients), urinary tract (16 patients), bone and joint (8 patients), primary bacteraemia (4 patients) and miscellaneous other sites (1 patient). Bacteria isolated included Staphylococcus aureus (65 patients), group A streptococcus (42 patients), Escherichia coli (17 patients), other Gram-negative bacilli (37 patients), anaerobic bacteria (34 patients) and other bacteria. Imipenem was more active than cephalothin in vitro against pathogenic bacteria isolated from evaluable patients. Cure or improvement was seen in 68 of the 72 imipenem-cilastatin patients (94%) and in 68 of the 69 cefazolin patients (99%). Relatively few abnormal laboratory tests and adverse experiences were noted, and there were no differences in this between the two treatment groups. We concluded that imipenem-cilastatin is safe at the dose used. It is as effective as cefazolin in mild to moderate infections caused by common pathogens. Further testing of imipenem-cilastatin in patients with more severe infections caused by bacteria, generally more resistant to antibiotics is justified.