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.