Comparative bioavailability and in vitro characterization of two brands of diclofenac sodium enteric-coated tablets

A bioavailability study and an in vitro characterization were conducted on two brands of diclofenac sodium enteric-coated tablets marketed in Jordan. The two brands were found similar in weight variation and content uniformity and both met the BP requirements of disintegration for enteric-coated tablets. The in vitro dissolution, according to the USP XXI method, revealed that brand B had significantly faster dissolution (99% of the drug dissolved in 1 h). The bioavailability was carried out on eight healthy male volunteers who received a single dose (2 x 50 mg) of each product in a crossover design. Blood samples were obtained over a 10 h interval and drug serum concentrations were determined using a sensitive HPLC assay. The two brands did not significantly differ with respect to peak serum concentration (4.4 and 4.5 micrograms.ml-1 for A and B, respectively) or to the lag time between dosing and the appearance of the drug in serum (1.06 and 0.88 h for A and B, respectively). Further, the two brands were not found significantly different with respect to the extent of absorption as indicated by the area under serum concentration-time curve (6.31 and 5.91 micrograms.h.ml-1 for A and B, respectively). Brand B, however, exhibited a significantly earlier time to attain peak serum concentration (1.2 h) compared to brand A (2.4 h). The difference in the tmax values is consistent with the in vitro dissolution pattern for the two brands.