Disclosed are drug delivery systems for the delivery of small molecule and macromolecular drugs. More particularly, disclosed are substituted analogs of 3,6-di(alkyl-4 aminobutyl)-2,5-diketopiperazine (which may also be referred to DKP), their use in the formulation of both small molecule and macromolecular drugs including therapeutic, prophylactic and diagnostic agents, stabilizing agents and systems for their delivery.
