The cocrystallization of adefovir dipivoxil (AD) with suberic acid (SUB) or succinic acid (SUC) was
examined. X-ray diffraction was used to determine the structures of AD/SUB and AD/SUC cocrystals. Both cocrystals were formed via multiple hydrogen bonds between the adenine part of AD and the
carboxylic acid groups of SUB or SUC. Longer SUB effectively dispersed AD molecules, and AD hydrogen-
bonded only to SUB. When shorter SUC was used, AD formed hydrogen bonding with both SUC and adjacent AD. As a result, the cocrystal compositions were AD/SUBผ1:1 and AD/SUCผ2:1. Both
cocrystals displayed superior thermal stability and increased aqueous solubility. The present study
demonstrated that the adenine and similar structures of active pharmaceutical ingredients could be
used to produce cocrystals of improved physical properties.