Evaluation of a New Cephalosporin Antibiotic, Cephapirin

Cephapirin sodium, a parenterally administered derivative of cephalosporanic acid, was tested in vitro against 150 stock cultures ofEnterobacteriaceae and 30 stock cultures each ofPseudomonas aeruginosa andStaphylococcus aureus . Both broth- and agar-dilution techniques were employed with two sizes of inocula of organisms. At a concentration of 7.5 μg or less/ml, cephapirin inhibited and killed 100% of strains ofEscherichia coli andProteus mirabilis and more than 80% ofKlebsiella species when tested against an inoculum of 105 bacterial cells/ml. However, even at 100 μg/ml, only a few isolates of otherEnterobacteriaceae andPseudomonas were inhibited. A 100-fold increase in the inoculum resulted in decreased susceptibility of organisms. All penicillin-susceptible as well as penicillin-resistantS. aureus isolates were inhibited and killed by 5 μg or less of cephapirin/ml when tested with an inoculum of either 104 or 106 organisms/ml. The drug also was studied in various doses in the treatment of 77 patients with diverse infections. Cephapirin was effective in the treatment of 27 of 32 patients with pulmonary infection, as well as in 6 of 7 patients with staphylococcal or streptococcal soft tissue infection. Of 25 patients with urinary-tract infections, 19 developed a negative culture during therapy. A single 4-g intramuscular dose of cephapirin was effective in only 2 of 11 patients with gonococcal urethritis or endocervicitis. Two patients with gonococcal urethritis treated with multiple injections were cured. The drug was well tolerated except for pain at the site of injection in 14 patients and phlebitis in 4 patients. No abnormalities in renal or hepatic function could be attributed to cephapirin. In addition, no abnormalities were found in the renal tubules of rabbits challenged with 500 mg of cephapirin/kg. If further studies document that cephapirin is well tolerated by the parenteral route, it may have advantages over cephalothin or cephaloridine.