Studies of Absorption, Excretion, Antibacterial and Clinical Effect of Cephalexin

Abstract

The in vitro antibacterial effect of cephalexin was determined for more than 200 bacterial strains. Pneumococci and Streptococcus pyogenes were inhibited by concentrations as low as 0.25–0.5 mcg/ml. With Staphylococcus aureus, both penicillinase producing and non-penicillinase-producing, Streptococcus viridans, Klebsiella-Enterobacter, Escherichia coli, Proteus mirabilis and Haemophilus influenzae, concentrations of cephalexin between 4 and 16 mcg/ml were necessary for inhibiting 50% of the strains. Most streptococci designated as enterococci and all Pseudomonas aeruginosa strains were regarded as resistant. The two methods used for testing antibacterial activity, serial dilution in agar and the disc method, were compared. The disc method was found suitable for routine sensitivity testing of cephalexin. The absorption and excretion of cephalexin was studied in 8 healthy human volunteers. Serum concentrations between 15 and 50 mcg/ml were reached within 1 hour after the administration of 1 g of the drug. More than 80% of the given dose could be recovered in the urine in the first 6 hours. The clinical effect of cephalexin was studied in 29 patients. Of these, 26 were considered as having proved or probable bacterial infections of various types. The primary result of the treatment was considered good in 18 cases, satisfactory in 3 cases, and poor in 5 cases. Cephalexin was shown to have an especially potent antibiotic effect in soft tissue infections caused by S. pyogenes and Staph. aureus. The side effects were few in number and not serious in nature. In 3 cases with diminished kidney function, slight accumulation of the drug in serum was shown after 5 days of therapy.