Effect of clavulanic acid on inactivated amoxicillin excretion in urinary tract infection.

Oral amoxicillin was taken with and without clavulanic acid by normal subjects and by patients with chronic complicated urinary tract infection to examine the in vitro protective effect of clavulanic acid on amoxicillin degradation. When amoxicillin alone was taken, urinary excretion of the penicilloic acid of amoxicillin in bacteria-positive patients was higher than that in bacteria-negative patients and in normal subjects. There was no comparable change in urinary penicilloic acid excretion in the presence of clavulanic acid. There were significant in vitro protective effects of clavulanic acid on beta-lactamases in the urine.