Co-crystal of Tramadol Hydrochloride–Celecoxib (ctc): A Novel API–API Co-crystal for the Treatment of Pain

We have identified a co-crystal of tramadol hydrochloride–celecoxib (ctc; E-58425/MR308), a novel active pharmaceutical ingredient (API)–API co-crystal formed by an intrinsic 1:1 molecular ratio of rac-tramadol·HCl and celecoxib, which displays favorable physicochemical and dissolution profiles. Adequate treatment of pain represents an unmet medical need that is often addressed via combination therapy. API–API co-crystals represent a new approach with potential to improve physicochemical properties, bioavailability, stability, or formulation capacity, which may translate into optimized pharmacokinetic profiles and clinical benefits compared with individual APIs or their combination. ctc showed a well-defined differential scanning calorimetry profile, and its single-crystal X-ray diffraction structure demonstrated a supramolecular 3D network in which the two active enantiomers of tramadol and celecoxib are linked via hydrogen bonding and chloride ions. Oversaturation studies indicated that the saturation e...