Abstract: The present invention relates to a carrier base for the topical delivery of an active agent comprising a high viscosity chitosan biopolymer. The invention further relates to a method of controlling the release of an active agent from a carrier base, comprising as a carrier base a high viscosity chitosan; providing the active agent; and mixing the active agent and the chitosan. Preferably, the carrier base comprises a high viscosity chitosan having a molecular weight of at least about 100,000 Dalton, more preferably at least about 250,000 Dalton and most preferably at least about 300,000 Dalton. In other preferred embodiments the chitosan has a concentration of at least about 2 weight %.