Particulate matter contamination in injectable drug products, especially in large numbers, can cause harm to patients. Common particulate sources include: solvent impurities, drug precipitates, dust, glass, rubber, environmental contaminants, fibers and other insoluble materials.
The size of particulate matter is an important factor when considering the potential risk to patients. Particles as small as 2 μm in diameter have been associated with microthrombi formation in patients. Dr. Michael Akers with the Food and Drug Administration notes that the smallest capillary blood vessels are considered to have a diameter of approximately 7 μm. Therefore, all particles having a size equal to or greater than 7 μm can conceivably become entrapped in and obstruct capillaries, increasing the potential for adverse effects. Simple visual inspection, which is required for compounded injections, may be adequate for large particles, but is inadequate for smaller particles. The lower limit of visibility of the naked eye is approximately 40 μm. Specialized testing methods are therefore necessary to adequately assess the total particulate burden of injections.