Excretion of antibiotics in bile.

The excretion of antibiotics in the bile of rats has been studied. Penicillins, including derivatives of 6-aminopenicillanic acid, are rapidly excreted, reabsorbed and re-excreted, in high concentration, whereas streptomycin, neomycin, paramomycin and chloramphenicol reach lower levels in the bile than in the plasma. p-Aminobenzylpenicillin and D(-)-6-(alpha-amino-alpha-phenylacetamido)penicillanic acid, both of which are bactericidal to Salmonellae and other coliforms, produce higher concentrations in the bile than benzylpenicillin (penicillin G). This may be of therapeutic importance.