Small filter membrane bags for the study of antibiotic action in the digestive tract: bioavailability and in situ efficacy of ampicillin in the pig caecum.

Bioavailability and activity of ampicillin were evaluated in the pig after preventive and curative doses by using small filter membrane bags containing strains of Escherichia coli placed into the caecum. A peak concentration of 720 micrograms ampicillin per ml was obtained in caecal liquor which was effective against E coli K82 and E coli 127 in the bags, in pigs orally administered with 20 mg/kg of the drug. After intramuscular injection of ampicillin with 40 mg/kg, the peak concentration in caecum reached 15 micrograms/ml but no activity against the strains of E coli K82 and 127 was recorded.