Clinical and laboratory evaluation of amoxicillin (BRL 2333) in the treatment of urinary tract infections.

Amoxicillin (alpha-amino-p-hydroxybenzyl penicillin) is a new oral semisynthetic penicillin with antibacterial activity similar to that of ampicillin; however, it is more completely absorbed and urinary concentrations are higher. Twenty-seven patients during 28 episodes of urinary tract infection were treated with oral amoxicillin given either as 250- or 500-mg doses. Clinical cure or improvement occurred in 23 of 27 infections (85%); eradication of the responsible organisms occurred in 23 of 26 infections (88%); and both clinical cure or improvement and eradication occurred in 20 of 25 infections (80%). Three infections relapsed. Failure to respond bacteriologically was associated with resistant organisms in two patients and with chronic pyelonephritis (Proteus mirabilis) is one. Concentrations of amoxicillin in serum obtained 2 h after administration were more variable than those previously reported for reasons which were obscure. In vitro studies revealed amoxicillin to be comparable to ampicillin when tested against most gram-negative bacilli; however, in this situation amoxicillin may be more effective than ampicillin against enterococci.