Re-evaluation of in vitro dissolution techniques for supersaturating drug delivery systems

Conventional dissolution testing using high-performance liquid chromatography (HPLC) analysis was evaluated against fiber optic dissolution method for studying supersaturable drug delivery systems. Two self-microemulsifying (SME) formulations of albendazole (ABZ) (15 mg/capsule and 5 mg/capsule) were prepared. Dissolution study was performed in medium with pH 1.2, 4.5, 6.8 and 7.4. Samples were analyzed simultaneously by HPLC and online fiber optic dissolution system. For 15 mg/capsule formulation, the profiles obtained using HPLC data showed almost 80-100% releases at pH 4.5, 6.8 and 7.4, whereas fiber optic data showed less than 40% release at the end of 60 min. The observed precipitation was due to pH-dependent solubility of ABZ in water and data analysis revealed a supersaturation phenomenon. This difference in release profiles was due to the presence of oil and water phase in the dissolution sample that upon dilution with high organic mobile phase resulted in quantification of the total drug and not the dissolved drug. The 5 mg/capsule formulation showed no difference in release profiles between methods as the concentration was under the saturation solubility. These results pointed out a considerable error in the development of a complex SME formulation, and use of fiber optic dissolution method was found beneficial.