The present invention relates to novel compositions for topical application and delivery of hydrophilic, biologically-active agents in a microemulsion to and through the protective outer layer of a biological surface, wherein a biological surface includes those of humans, animals, viruses, protozoa, fungi, and bacteria. One issue in relation to hydrophilic biologically-active agents, such as pharmaceutical drugs, antimicrobial agents, anti-infective agents, and pain-relieving agents is that they are not soluble in the hydrophobic volatile solvents. This issue is addressed by the present invention by the provision of a composition comprising a reverse microemulsion comprising at least one hydrophilic, biologically-active agent solubilized by a hydrophobic reverse emulsion surfactant in a non-stinging, volatile, hydrophobic solvent, and a polymer substrate soluble in the non-stinging, volatile, hydrophobic solvent, wherein said non-stinging, volatile, hydrophobic solvent is selected from the group consisting of volatile linear and cyclic siloxanes, volatile linear, branched and cyclic alkanes, and combinations thereof. The polymeric substrate is included for adsorption of the biologically-active agent which, after evaporation of the volatile solvent, provides sustained release of the biologically active agent to the biological surface on which it is deposited. In addition, the water-in-oil microemulsions of the compositions described herein exhibit slow release of the water-soluble biologically-active agents.
