Unorthodox crystalline drug salts via the reaction of amine-containing drugs with CO2.

Drugs containing amine groups react with CO2 to form crystalline ammonium carbamates or carbamic acids. In this approach, both the cation and anion of the salt, or the neutral CO2 adduct, are derived from the parent drug, generating new crystalline versions in a 'masked' or prodrug form. It is proposed that this approach may serve as a valuable new tool in engineering the physical properties of drugs for formulation purposes.