Patent ID: RE39588

Claim:
A controlled release medical device for delivery of at least one therapeutic agent in a pre-determined delivery rate pattern to a biological environment comprising, in combination: reservoir means containing a therapeutic agent which in a first form as a salt is suitable for storage and in a second form is a member selected from the group consisting of a free acid, a free base and an ester, is suitable for absorption through the skin or mucosa, and said reservoir means having a surface substantially impermeable to said therapeutic agent in said first form and permeable to said therapeutic agent in said second form and through which the second form of said therapeutic agent is released to the biological environment; and activating means containing an activating agent wherein said activating agent in a first state is anhydrous, and in a second state is hydrated and in solution wherein said means is in the anhydrous form; whereby the therapeutic agent is changed from its first to its second form by the activating means in its second state and whereby the passage of therapeutic agent to the biological environment by diffusion is impeded until the therapeutic agent changes form.