Rapid Identification And Morphology Evaluation Of Solid Pharmaceutical Excipients

Introduction
A solid dosage form of a pharmaceutical tablet or capsule often contains a small amount of active drug substance, while the rest of the formulation is inactive ingredients, or "excipients." These excipients have very specific functions, acting as fillers, binders, lubricants, preservatives, solubility enhancers, or antioxidants. The particular formulation of a drug, which is the combination of excipients and active ingredient, ultimately affects the drug bioavailability.

As is the case with active drug substances, excipients must be controlled and examined for batch to batch variability, stability in the formulation, etc. Since excipients in solid dosage forms are often crystalline, polarized light microscopy (PLM) is a useful technique for characterizing them. However, this requires a skilled microscopist to interpret the sometimes subtle differences in PL images of different crystals. Ideally, PLM should be combined with a confirmatory analytical method that can identify solid excipients quickly and reliably in conjunction with light microscopy.