Single‐dose pharmacokinetics of co‐crystal of tramadol–celecoxib: Results of a four‐way randomized open‐label phase I clinical trial in healthy subjects

AIMS Co-crystal of tramadol-celecoxib (CTC) is a novel co-crystal molecule containing two active pharmaceutical ingredients under development by Esteve (E-58425) and Mundipharma Research (MR308). This Phase I study compared single-dose pharmacokinetics (PK) of CTC with those of the individual reference products [immediate-release (IR) tramadol and celecoxib] alone and in open combination. METHODS Healthy adults aged 18-55 years were orally administered four treatments under fasted conditions (separated by 7-day wash-out period): 200 mg IR CTC (equivalent to 88 mg tramadol and 112 mg celecoxib; Treatment 1); 100 mg IR tramadol (Treatment 2); 100 mg celecoxib (Treatment 3); and 100 mg IR tramadol and 100 mg celecoxib (Treatment 4). Treatment sequence was assigned using computer-generated randomization. PK parameters were calculated using noncompartmental analysis with parameters for CTC adjusted according to reference product dose (100 mg). RESULTS Thirty-six subjects (28 male, mean age 36 years) participated. Tramadol PK parameters for Treatments-1, -2 and -4, respectively, were 263, 346 and 349 ng ml-1 (mean maximum plasma concentration); 3039, 2979 and 3119 ng h ml-1 (mean cumulative area under the plasma concentration-time curve); and 2.7, 1.8 and 1.8 h (median time to maximum plasma concentration). For Treatments 1, 3 and 4, the respective celecoxib PK parameters were 313, 449 and 284 ng ml-1 ; 2183, 3093 and 2856 ng h ml-1 ; and 1.5, 2.3 and 3.0 h. No unexpected adverse events were reported. CONCLUSION PK parameters of each API in CTC were modified by co-crystallization compared with marketed formulations of tramadol, celecoxib, and their open combination.