Bioavailability of ibuprofen following oral administration of standard ibuprofen, sodium ibuprofen or ibuprofen acid incorporating poloxamer in healthy volunteers

BACKGROUND The aim of this study was to compare the pharmacokinetic properties of sodium ibuprofen and ibuprofen acid incorporating poloxamer with standard ibuprofen acid tablets. METHODS Twenty-two healthy volunteers were enrolled into this randomised, single-dose, 3-way crossover, open-label, single-centre, pharmacokinetic study. After 14 hours' fasting, participants received a single dose of 2x200 mg ibuprofen acid tablets (standard ibuprofen), 2x256 mg ibuprofen sodium dihydrate tablets (sodium ibuprofen; each equivalent to 200 mg ibuprofen acid) and 2x200 mg ibuprofen acid incorporating 60 mg poloxamer 407 (ibuprofen/poloxamer). A washout period of 2-7 days separated consecutive dosing days. On each of the 3 treatment days, blood samples were collected post dose for pharmacokinetic analyses and any adverse events recorded. Plasma concentration of ibuprofen was assessed using a liquid chromatographic-mass spectrometry procedure in negative ion mode. A standard statistical ANOVA model, appropriate for bioequivalence studies, was used and ratios of 90% confidence intervals (CIs) were calculated. RESULTS Tmax for sodium ibuprofen was less than half that of standard ibuprofen (median 35 min vs 90 min, respectively; P=0.0002) and Cmax was significantly higher (41.47 microg/mL vs 31.88 microg/mL; ratio test/reference=130.06%, 90% CI 118.86-142.32%). Ibuprofen/poloxamer was bioequivalent to the standard ibuprofen formulation, despite its Tmax being on average 20 minutes shorter than standard ibuprofen (median 75 mins vs 90 mins, respectively; P=0.1913), as the ratio of test/reference=110.48% (CI 100.96-120.89%), which fell within the 80-125% limit of the CPMP and FDA guidelines for bioequivalence. The overall extent of absorption was similar for the three formulations, which were all well tolerated. CONCLUSION In terms of Tmax, ibuprofen formulated as a sodium salt was absorbed twice as quickly as from standard ibuprofen acid. The addition of poloxamer to ibuprofen acid did not significantly affect absorption.