Expanding the Crystal Form Landscape of the Antiviral Drug Adefovir Dipivoxil

The solid state of adefovir dipivoxil
(AD) has been revisited.
In the present article we extend the knowledge about the solid state
of this pharmaceutical prodrug. The stability landscape of the amorphous
form with respect to the anhydrous and hydrate crystalline forms has
been studied, and the use of an antiplasticizing agent to increase
its Tg is described. The crystal structure of the elusive anhydrous
form I has been determined from laboratory powder X-ray diffraction
data by means of direct space methods using the computing program
FOX. In addition, three new isostructural solvates of AD (methanol,
ethylenglycol, and methylethylketone) have been discovered and structurally
characterized by single crystal X-ray diffraction.