Fate Of Selected Cephalosporins In The Alimentary Tract Of Rats

Cephalexin, cephaloridine and 7-(thienyl-2′-acetamido)-3-methylceph-3-em-4-carboxylic acid (TMC) were injected directly into the alimentary tract of rats and their subsequent fate was studied. The three antibiotics showed respectively good, poor and intermediate degrees of absorption from the alimentary tract. These differences are attributable to the rate at which each antibiotic is absorbed from the small intestine and not to the amount of degradation that occurs in the gut.

Cephalexin is much more rapidly absorbed from the small intestine than are cephaloridine and TMC. Cephalosporins that are not absorbed in the small intestine pass down the alimentary tract and are destroyed when they reach the caecum, from which there is little absorption.