This invention provides for a therapeutic system for timed and controlled release of at least one therapeutic active agent to a human or animal organism by diffusion through the skin or mucous membrane. The active agent is initially present, for the purposes of manufacture and storage, in a first state in the form of a pharmaceutically acceptable salt, which is chemically stable and insufficiently permeable for the skin or mucous membrane. The active agent is converted at the application site upon access of moisture and by an activating agent into a second state, which is suitable for diffusion through the skin or mucous membrane and in which it is taken up by the organism. The activating agent is initially present as a solid substance or a mixture or a plurality of such substances, which reacts in aqueous solution as an acid or base. The activating agent contains a portion of water of at least 5% in its solid body structure, either intercalated or bound thereto.