26 Because of the pixel size of 2 μm3, uncertainty remains about the presence
of nano-sized amorphous drug particles. The fusion method is sometimes referred to as the melt method, which is correct only when the starting materials are crystalline. Melting method was first used to prepare simple eutectic mixtures by Sekiguchi and Obi Leuner and Dressman (2000) used to describe melting method as hot melt method. This method consists of melting the drug within the carrier followed by cooling and pulverization of the obtained product. The process has got some limitations like, use of high temperature and chance of degradation of drug during melting, incomplete miscibility between drug and carrier.27 The melting or fusion method is the preparation selleck of physical mixture of a drug and a water-soluble carrier and heating it directly until it melted. The melted mixture is then solidified rapidly in an ice-bath under vigorous stirring. The final solid mass is crushed, pulverized and sieved. Appropriately this has undergone many modifications in pouring the homogenous melt in the form of a thin layer onto a ferrite plate or a stainless steel plate and cooled by flowing air or water on the opposite side of the plate. In addition, a super-saturation of a solute or drug in a system can
often be obtained by quenching the melt rapidly from a high temperature.28 Under ZD1839 solubility dmso such conditions, the solute molecule is arrested in the solvent matrix by the instantaneous solidification process. The quenching technique gives a much finer dispersion of crystallites when used for simple eutectic mixtures. The drugs were ball milled in a mixer mill (Glen Creston Ltd., Loughborough, UK) using a 25 mL
chamber for 120 min at oxyclozanide 2% w/v with 2–12 mm diameter and 6–7 mm diameter stainless steel ball bearings.29 The samples were milled at 17.5/s.1. Solvent evaporation method is a simple way to produce amorphous solid dispersions where the drug and carrier is solubilized in a volatile solvent.30 The first step in the solvent method is the preparation of a solution containing both matrix material and drug. The second step involves the removal of solvent(s) resulting in formation of a solid dispersion.30 Mixing at the molecular level is preferred, because this leads to optimal dissolution properties. Using the solvent method, the pharmaceutical engineer faces two challenges.31 The first challenge is to mix both drug and matrix in one solution, which is difficult when they differ significantly in polarity. To minimize the drug particle size in the solid dispersion, the drug and matrix have to be dispersed in the solvent as fine as possible preferably drug and matrix material are in the dissolved state in one solution. The second challenge in the solvent method is to prevent phase separation, e.g. crystallization of either drug or matrix, during removal of the solvent(s).