Amoxicillin in infections in patients with cancer.

Abstract

The antibacterial activity of amoxicillin was tested in vitro against 126 clinical isolates of gram-positive cocci and 250 isolates of gram-negative bacilli. Most strains of penicillin G-sensitive Staphylococcus aureus, Streptococcus pyogenes, and Diplococcus pneumoniae were inhibited by <0.1 [tg/ml. Of Proteus mirabilis isolates, 76% were susceptible to (<1.56 tg of amoxicillin/ml, but 20% were resistant to 12.5 qtg/ml. Fifty-seven percent of Escherichia coli isolates were susceptible to <6.25 ttg/ml, but most of the remaining isolates were resistant to 50 [tg/ml. Clinical pharmacologic studies were conducted with 11 adult volunteers. The mean peak concentration in serum after the 125-mg dose (2.3 [tg/ml) was achieved at 1 hr. The mean peak concentration in serum after the 250-mg dose (3.4 ptg/ml) occurred between 1 and 2 hr. After a dose of 500 mg of amoxicillin, the mean peak concentration in serum (6.8 [tg/ml) occurred at 2 hr. The mean proportion of the drug excreted in the urine with each dose varied between 70% and 78%. Amoxicillin was used for treatment of nonbacteremic infections in 35 patients with cancer. The best responses were obtained against infections caused by gram-positive cocci (100%), P. mirabilis (100%), and E. coli (69%). The response correlated with the in vitro sensitivity to ampicillin. Three patients experienced side effects.