Liquid membrane phenomena and drug action

Abstract

A wide variety of drugs are known to ber surface active and in a number of cases excellent correlations between surface activity and biological effects have been demonstrated. This fact indicates the possibility of a common mode of action for all surface active drugs. Literature reports on the surface activity of drugs indicating such a possibility are reviewed. Recent investigation on structurally dissimilar drugs of different pharmacological categories have revealed that the liquid membranes which are likely to be generated by the surface active drugs at the respective sites of action may act as a barrier to the transport of relevant permeants. The formation of such liquid membranes migh be an important step common to the mechanism of action of all surface active drugs. A consolidated account of all such investigations is presented. This concept that liquid membrane barriers generated by the drug itself modify access of the relevant permeants to the receptor site has been discussed in the light of existing theories of drug action, particularly the occupancy theory and the rate theory. As a result of this discussion, a more rational biophysical explanation for the action of such drugs which act by modifying the permeability of cell membranes has emerged.