EFFECT OF SALICYLIC-ACID ENCAPSULATION BY PHOSPHOLIPID-VESICLES ON TRANSPORT THROUGH AN INERT MEMBRANE

Salicylic acid (SA) was incorporated into phospholipid vesicles based on Phospholipon(R) 80. Entrapment of SA and flux through an inert memb rane (Silastic(R)) were a function of pH. From mathematical treatment of data obtained at more than one value of pH, the relative contributi ons of ionized and unionized species were determined. Both entrapment and flux were dominated by the uncharged form of the compound. An incr ease in lipid concentration resulted in an increase in entrapment and corresponding reduction in the steady-state flux of SA through the mem brane. The SA permeation pattern following liposome application under finite dose conditions was qualitatively different from that in buffer . Penetration from liposomes was slower, and the amount crossing the m embrane at 24 hours was significantly less.