The incorporation of drug molecules with poor water solubility into polypyrrole as dopants: Indomethacin and sulindac

There is considerable interest in the development of polypyrrole–based drug delivery systems. However, it is not possible to incorporate drugs with limited water solubility into polypyrrole from the usual aqueous–based electropolymerisation solutions. In this study, two drugs with poor solubility in water, sulindac and indomethacin, were incorporated within polypyrrole films as dopants from an ethanol–containing electropolymerisation solution to give PPyIndo and PPySul. An organic perchlorate salt was added to the electropolymerisation solution and the resulting perchlorate dopant anions were released initially on reducing the PPyIndo and PPySul at −0.70 V vs SCE. The drug molecules were then re–doped in the absence of the perchlorate salt. On reduction of the polymer films the sulindac and indomethacin were released into an aqueous saline solution, giving approximately 0.12 mg cm−2 of sulindac and 0.29 mg cm−2 of indomethacin over a 60 min release period. The greater amounts of indomethacin released from PPyIndo were explained in terms of higher doping levels. The doping levels of indomethacin and sulindac were estimated at 0.28 and 0.10, respectively, using electrochemical quartz crystal microbalance measurements