Luca Dobetti

Enhancement and Modification of Etoposide Release from Crospovidone Particles Loaded with Oil-Surfactant Blends

A novel solid formulation for oral delivery of pH-sensitive, scarcely water-soluble etoposide has been designed, characterized, and tested in vitro. The purpose of this study was to assess the performance of the new dosage forms, in comparison to marketed, liquid-filled capsules. The solid formulation was developed by grinding the drug with a cross-linked polymeric carrier (crospovidone) under controlled process conditions (mechano-physical drug activation), and subsequently incorporating selected oil/surfactant (o/s) blends into the polymer particles. Physicochemical characterization (thermal analysis, drug dissolution kinetics, drug o/w partition studies) provided information on drug-polymer interaction at the solid state, and on the formulation performance in vitro, resulting in the enhancement and modification of the etoposide solubilization process. DSC thermograms showed the amorphous or nanocrystalline state of etoposide within the carrier, as indicated by the shifting of DSC peaks (delta T > -10 degrees C). Solubility kinetics of etoposide in oversaturation conditions were strongly affected by the chemical nature of the vehicle used: short-chain triglycerides afforded drug concentrations well above 600 micrograms ml-1 for more than 3 hr, versus a drug equilibrium solubility of approximately 150 micrograms ml-1. Drug dissolution curves under sink conditions were superimposable to those of liquid-filled capsules available on the market (Vepesid 50, Bristol-Myers Squibb), yielding 100% drug release in 10 min. The oil phase/water partition coefficient of etoposide (P) was affected by the surfactant concentration. The biphasic trend observed in P values suggested a dual mechanism in drug release from polymeric particles: the presence of oily vehicles and surfactants in the formulation could create, upon release, a favorable environment to sustain etoposide dissolution, slowing down drug reprecipitation. Such solid formulation could be considered equivalent, in vitro, to the current marketed product.