Enhancement of the rectal absorption of sodium ampicillin by N-acylamino acids in rats.

The promoting efficacies of N-acyl derivatives of amino acids on the rectal absorption of sodium ampicillin were investigated using the rat rectal loop technique. N-Acyl derivatives with longer carbon chains in the acyl moiety showed a greater promoting potency. The promoting potencies of N-acyl derivatives of phenylglycine and phenylalanine were greater than those of glycine and alanine derivatives when compared at the same length of carbon chain in their acyl moieties. The promoting action of N-acylamino acids was not influenced by the presence of N-ethylmaleimide or ouabain. The promoting potencies of N-acylamino acids were depressed in the presence of calcium chloride in the rectal loop. The contribution of the calcium ion sequestration capacity of N-acylamino acids to their promoting efficacies is discussed.