Cephapirin sodium, a parenterally administered derivative of
cephalosporanic acid, was tested in vitro against 150 stock cultures of Enterobacteriaceae and 30 stock cultures each of Pseudomonas aeruginosa and Staphylococcus aureus. Both broth- and
agar-dilution techniques were employed with two sizes of inocula of organisms. At a concentration of 7.5 mug or less/ml,
cephapirin inhibited and killed 100% of strains of Escherichia coli and Proteus mirabilis and more than 80% of Klebsiella species when tested against an inoculum of 10(5) bacterial cells/ml. However, even at 100 mug/ml, only a few isolates of other Enterobacteriaceae and Pseudomonas were inhibited. A 100-fold increase in the inoculum resulted in decreased susceptibility of organisms. All
penicillin-susceptible as well as
penicillin-resistant S. aureus isolates were inhibited and killed by 5 mug or less of
cephapirin/ml when tested with an inoculum of either 10(4) or 10(6) 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.