Comparative in vivo activity of bacampicillin and amoxycillin

Bacampicillin is an orally well-absorbed pro-drug of ampicillin giving high in vivo levels of the latter. Its therapeutic activity was compared with that of amoxycillin in two experimental infection models in mice. The animals were infected with suspensions of Escherichia coli III and Haemophilus influenzae 22863 intraperitoneally and treated orally four hours afterwards with one of the two compounds. The antibacterial activity of the compounds was determined as CD50 values or by making viable counts in the blood and in organ homogenates of the animals. Ampicillin and amoxycillin had the same inhibitory but different bactericidal activity against the test strains. Both compounds appeared to have similar therapeutic activity and were found to cause a rapid decrease of the bacterial counts in the animals. Bacampicillin appeared to give a more rapid bactericidal activity than amoxycillin against the Haemophilus influenzae strain, whereas amoxycillin initially appeared more bactericidal against the Escherichia coli infection.