In this work, the formation and stability of amorphous solid dispersions (SDs) as orodispersible films (ODF) were investigated using tetrabenazine (TBZ) as a poorly water soluble drug. The influence of polymer nature and pH-modifier incorporation to form and maintain SDs was investigated.
TBZ-loaded ODF were formulated using 4 different polymers (HPMC, PVP, Pullulan, and HEC). Binary systems (BS) were obtained mixing the drug with different polymers, while ternary (TS) systems were also obtained by adding citric acid to solubilize TBZ in the mixture. Drug dissolution studies, thermal analysis and X-ray diffraction were carried out to characterize the physical state of API in ODF.
ODF made of TS allowed a major improvement of TBZ dissolution profile in buccal conditions compared to a pure drug or BS. DSC and X-ray diffraction revealed that API was in amorphous state in TS while remained crystalline in BS. Following 6 months of storage, TBZ recrystallization occurred for PVP-TS and HEC-TS which induced a decrease of drug release in saliva conditions. HPMC and PUL-TS maintained API in amorphous state during 6 months. Briefly, amorphous SDs were obtained by the pre-dissolution of the drug in acidified water and incorporation in polymeric films. The miscibility and potential interaction between TBZ and polymers have been identified as important factor to explain stability differences.