Understanding the Impact of Particle Size and Crystal Habit of Mesalamine Drug Substances on Their Packing, Wetting, and Dissolution Behaviour: A Science-based Approach for Selection of API Vendor.

Solid-state pharmaceutical properties play a pivotal role in determining product performance, manufacturing consistency, and clinical outcomes, especially for high-dose active pharmaceutical ingredients (APIs). Mesalamine (MES), a BCS class IV drug, has the highest unit dose of 4000 mg and is available as prolonged-release granules for oral administration. MES delayed-release tablets are available in different strengths of 400, 800, and 1200 mg. In this study, five MES API samples from various manufacturers were evaluated for crystal morphology, bulk properties, crystallinity, thermal behaviour, solubility, wettability, and dissolution performance. No significant difference was observed in particle size (Dv 50 ranging from 38.2 to 63.7 µm). Crystals, including needles, rectangular bars, and mixed morphologies, were observed in APIs from different manufacturers, resulting in distinct surface and packing characteristics. The rectangular bar crystal habit of API D likely results in parallel packing during compaction, exposing basal faces on the tablet surface. The higher contact angle of 53.0 ± 0.6° was observed with API D. In contrast to contact angle, it was observed that the high saturation solubility (3.4 mg/mL in pH 7.2 and 7.4) and higher extent of dissolution (95.3 ± 2.3%) for API D, when compared with rest of APIs, this could be due to the presence of a hydrophilic carboxylic group on the edge of the crystal lattice, which promotes the higher surface polarity. The present study demonstrated that the rectangular bar crystal habit has more suitable manufacturing and favourable biopharmaceutical properties for the manufacture of dosage forms.