A new cephalosporin derivative (ST-21) orally administered in laboratory animals.

The pivaloxymethyl ester of 7-(D-2-amino-2-phenylacetamido)-desacetoxicephalosporanic acid hydrochloride (ST-21) and cephalexin possess the same bacteridal activity. In fact, in the animal body ST-21 releases cephalexin. The acute toxicity study shows the good tolerance of both substances, whereas the tissue distribution is different, both after oral and i.v. administration. Cephalexin concentrations in some tissues of rats and rabbits, particularly in the lungs and kidneys, are higher and longer-lasting in the animals treated with ST-21 than in those receiving cephalexin, thus showing a different pattern of distribution in the body. For this reason ST-21 might be more suited for the treatment of lung and kidney infections.