Patent ID: 7799344

Claim:
A method for coating a preformed crystalline microparticle with an active agent in a suspension, said method comprising the steps in the sequence set forth of: i) obtaining a preformed crystalline diketopiperazine microparticle wherein said preformed crystalline diketopiperazine microparticle does not comprise an active agent; ii) providing a suspension comprising said preformed crystalline diketopiperazine microparticle, said active agent, and a solvent; iii) then altering suspension conditions in said provided suspension to modify an energetic interaction between said active agent and said preformed crystalline diketopiperazine microparticle wherein said altering suspension conditions is selected from the group consisting of altering the pH of the solvent, adding monovalent or multivalent ions, altering the polarity, and adding hydrogen bond donors or acceptors to modify a surface property of said preformed crystalline diketopiperazine microparticle wherein said altering step does not include a step of removing said solvent from said suspension; and iv) adsorbing said active agent onto a surface of said preformed crystalline diketopiperazine microparticle to provide a coating of said active agent on said crystalline microparticle without removing solvent from said suspension; wherein said altering step causes said adsorbing of said active agent onto a surface of said preformed crystalline diketopiperazine microparticle.