Amoxicillin trihydrate, a number of so-called broad spectrum penicillins, is enzymatic or chemically synthesized from 6-APA [
A0800]. It is a congener of ampicillin [
A2092] differing from the parent antibiotic only by hydroxylation of the phenyl side chain. That amino group helps the drug penetrate the outer membrane of Gram-negative bacteria. Amoxicillin has ampicillin like activity against not only Gram-positive but also Gram-negative bacteria. Meanwhile, amoxicillin is absorbed when given orally, achieving blood concentrations approximately twice as high as those obtained with ampicillin. Amoxicillin acts as a competitive inhibitor of the enzyme transpeptidase, which is needed by bacteria to make their cell walls. Its spectrum of activity is enhanced by co-administration of sulbactam [
S0868] or clavulanic acid, an antibiotic that inhibits beta lactamase an enzyme produced by bacteria to inactivate amoxicillin. Recently, combinations of amoxicillin, proton pump inhibitor (PPI) and clarithromycin [
C2220] or another antibiotic have been reported to be effective in the treatment of
Helicobacter pylori infection.