Possible mechanism behind the adjuvant action of phosphate derivatives on rectal absorption of cefoxitin in rats and dogs.

The mechanism underlying the ability of phosphate derivatives to act as adjuvants and coadjuvants was examined in in vivo and in situ preparations in rats and dogs. The adjuvant effect of DL-alpha-glycerophosphate on the rectal absorption of sodium cefoxitin was greatly augmented by the presence of either sodium phytate or sodium tripolyphosphate. These coadjuvants only slightly enhanced cefoxitin rectal absorption when administered alone. Therefore, enhancement of the permeation of tripolyphosphate and phytate by alpha-glycerophosphate may be necessary before the coadjuvants can significantly affect cefoxitin absorption. The inhibitory effect of disodium 4,4'-diisothiocyano-2,2'-disulfonate stilbene, which is known to interact with the amino group in the protein fraction, on enhanced cefoxitin absorption suggests the involvement of the protein fraction in transport of cefoxitin across the rectal membrane.