title: Dissolution and precipitation behavior of amorphous solid dispersions.
abstract: Amorphous solid dispersions (ASDs) are widely utilized in the pharmaceutical industry for bioavailability enhancement of low solubility drugs. The important factors governing the dissolution behavior of these systems are still far from adequately understood. As a consequence, it is of interest to investigate the behavior of these systems during the dissolution process. The purpose of this research was twofold. First, the degree of supersaturation generated upon dissolution as a function of drug-polymer composition was investigated. Second, an investigation was conducted to correlate physical behavior upon dissolution with polymer loading. Felodipine and indomethacin were selected as model drugs and hydroxypropylmethylcellulose (HPMC) and polyvinylpyrrolidone (PVP) were used to form the dispersions. Diffusion and nuclear magnetic resonance spectroscopy experiments revealed that the extent of bulk supersaturation generated on dissolution of the ASD did not depend on the drug-polymer ratio. Interestingly, the maximum supersaturation generated was similar to the predicted amorphous solubility advantage. However, dynamic light scattering measurements revealed that particles on the submicron scale were generated during dissolution of the solid dispersions containing 90% polymer, whereas solid dispersions at a 50% polymer loading did not yield these nanoparticles. The nanoparticles were found to result in anomalous concentration measurements when using in situ ultraviolet spectroscopy. The supersaturation generated upon dissolution of the solid dispersions was maintained for biologically relevant timeframes for the HPMC dispersions, whereas PVP appeared to be a less effective crystallization inhibitor.
authors: Department of Industrial and Physical Pharmacy, College of Pharmacy, Purdue University, West Lafayette, Indiana 47907; Global Pharmaceutical Research and Development, Abbott Laboratories, Abbott Park, Illinois 60064.
authors: David E
authors: DE
authors: Alonzo
authors: Global Pharmaceutical Research and Development, Abbott Laboratories, Abbott Park, Illinois 60064.
authors: Yi
authors: Y
authors: Gao
authors: Global Pharmaceutical Operations, Abbott Laboratories, North Chicago, Illinois 60064.
authors: Deliang
authors: D
authors: Zhou
authors: Department of Medicinal Chemistry and Molecular Pharmacology, Purdue InterdepartmentalnmR Facility, College of Pharmacy, Purdue University, West Lafayette, Indiana 47907.
authors: Huaping
authors: H
authors: Mo
authors: Global Pharmaceutical Research and Development, Abbott Laboratories, Abbott Park, Illinois 60064. Electronic address: geoff.gz.zhang@abbott.com.
authors: Geoff G Z
authors: GGZ
authors: Zhang
authors: Department of Industrial and Physical Pharmacy, College of Pharmacy, Purdue University, West Lafayette, Indiana 47907. Electronic address: lstaylor@purdue.edu.
authors: Lynne S
authors: LS
authors: Taylor