Comparative bioavailability of two different diclofenac formulations in healthy volunteers

The aim of the study was to assess the bioequivalence of two different dicl ofenac (CAS 15307-86-5) formulations (diclofenac free acid suspension as te st formulation and diclofenac resinate suspension, Cataflam(R), as referenc e formulation) in 24 healthy volunteers. After an overnight fast, the volun teers received a single oral dose (50 mg) of each formulation, following an open, randomized, two-period crossover design, with a fourteen-day washout interval between doses. Serum samples were obtained over a 24-h interval p ost-dosing, and were analysed for their diclofenac content by HPLC-UV. No a dverse effect was reported for any of the formulations administered. Geomet ric mean test/reference individual ratios were: 92.8 % for AUC((0-24 h)), 9 3.2 % for AUC((0-infinity)), 117.2 % for C-max, 131.0 % for K-e and 76.2 % for T-1/2. The variability of C-max parameter expressed as CV was greater t han 25 %. Since the 90 % CI for AUC((0-24 h)) mean ratio were within the 80 -125 % interval proposed by the Food and Drug Administration, it can be con cluded that diclofenac free acid formulation is bioequivalent to diclofenac resinate formulation for the extent of absorption. Since the European Comm unity Agency accepts a 90 % CI for C-max of 70-143 %, it can be concluded t hat diclofenac free acid formulation is bioequivalent to diclofenac resinat e formulation for both the rate and the extent of absorption after single d ose administration.