Delivery of therapeutic agents
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The present invention relates to a composition of matter for the time-dependent liberation of therapeutic agents. This composition of matter comprises a polymeric slab and a homogeneously dispersed enzyme which degrades the polymeric slab in the presence of moisture. The therapeutic agent is physically entrapped in the polymeric slab by inclusion during polymerization to form the polymeric slab or by mixture of the therapeutic agent with a liquid form of the polymeric slab and conversion of the liquid to a solid form. The therapeutic agent is not chemically bound to the polymer, and thus release of the agent is immediately effected upon the specific moisture-activated enzymatic degradation of the polymer slab. Moisture for enzymatic activation is provided by the biological surface on which the slab is emplaced, such as the dermal surface. The composition comprises a polymer such as poly (DL-lactide) and an enzyme such as proteinase K together with chlorpheniramine maleate as the therapeutic agent.