Cortisone and cortisol break hydrogen-bonding rules to make a drug-prodrug solid solution.

Multidrug products enable more effective therapies and simpler administration regimens, provided that a stable formulation is prepared, with the desired composition. In this view, solid solutions have the advantage of combining the stability of a single crystalline phase with the potential of stoichiometry variation of a mixture. Here a drug-prodrug solid solution of cortisone and cortisol (hydrocortisone) is described. Despite the structural differences of the two components, the new phase is obtained both from solution and by supercritical CO2 assisted spray drying. In particular, to enter the solid solution, hydrocortisone must violate Etter's rules for hydrogen bonding. As a result, its dissolution rate is almost doubled.