Some physicochemical properties of mefenamic acid.

Mefenamic acid is a problematic drug in granulation, tableting, and dissolution due to its poor solubility, hydrophobicity, and tendency to stick to surfaces. In most cases, the specifications of a drug by the pharmacopoeia include identification and purity, but they do not describe the physicochemical drug properties precisely. To characterize the mefenamic acid particle size, surface area measurements, X-ray pattern, differential scanning calorimetry (DSC), wettability, crystal habit, and compression behavior of different batches from two manufacturers were investigated. Due to larger particle size and better wettability, mefenamic acid of Il Yang type was easier to handle in a granulation process. The compression behavior of both types was nearly the same, although particle size, crystal habit, and wettability were very different.