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Description
ABSTRACT
The powder blending process has been historically identified as a challenging operation in Oral Solid Dosage (OSD) form manufacturing. Insufficient blending results in poor active ingredient mixing with excipients. Excessive blending could adversely impact the distribution of drug content (content uniformity) in the final product. Companies suffer financial setbacks due to rework of poor quality product, and more severely, legal action being taken because of non-compliance. With harmonizing efforts, government agencies, such as the U.S. Food and Drug Administration (FDA), join with industry experts and scientists to develop corresponding principles and guidelines in order to assist drug manufacturers. According to the FDA's current Good Manufacturing Practice (cGMP) Code of Federal Regulations (CFR), Title 21, Part 211-Current Good Manufacturing Practice for Finished Pharmaceuticals standard; particularly section 211.110, Sampling and testing of in-process materials and drug products of Subpart F states, written procedures shall be established and followed for "adequacy of mixing to assure uniformity and homogeneity ..." In the following blend uniformity discussion, we will examine this rule and demonstrate how guidelines emerge, how they are interpreted, and their practical adoption to current industrial methodologies and/or technologies.
OVERVIEW OF BLENDING PROCESS AND EQUIPMENT
The process of blending is commonly defined in the pharmaceutical industry as: the mixing of various bulk powder ingredients (e.g., drugs, excipients), targeted for a homogeneity and uniform distribution of the mixture. Each pharmaceutical product has its unique blend of raw materials; therefore, a careful selection of manufacturing process equipment and methods is inevitable. The quality of the resulting blend depends highly on the types of blenders or mixers used; the "flowability" (flow behavior) of powder during the blend cycle is factored into the finished product quality. The mechanics of blending, which involves the principles of shear, convection, and diffusion (or dispersion), is achieved by the use of industrial blenders or mixers. The equipment employed to accomplish the process of blending can be categorized as either rotating or fixed shell blenders. Rotating shell blenders (i.e., drum, cross-flow, double cone, and twin-shell) accomplish the mixing process by rotating the blender shell around a fixed axis and by relying upon a sliding or rolling motion of the powder. To aid in this mixing process, many systems will utilize internal baffles. Fixed shell blenders (i.e., ribbon, screw, and impeller mixers), on the other hand, rotate internal blender parts, such as an impeller or paddle, and produce a continuous cutting and shuffling motion. Shearing force that breaks apart large conglomerates of powder is, therefore, developed by this kind of cutting and shuffling motion. Pony, planetary, and high shear mixers are commonly used in... |
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