A comparative bioavailability study on two sustained-release formulations of diclofenac sodium following a single dose administration.

A single dose comparative bioavailability study and an in vitro evaluation were conducted on two sustained-release formulations of diclofenac sodium (Voltaren "V" and Diclogesic "D"). The two products were found similar in weight and content uniformity. The in vitro dissolution, however, revealed that product D has a significantly faster rate of drug release compared to product V. The bioavailability study was carried out on 15 healthy male volunteers, who received a single oral dose (100 mg tablet) of each product according to a randomized crossover design. Blood samples were obtained over a 12 h period, and drug concentrations were determined by an HPLC assay. The two products were not found to be statistically different with respect to the lag time between dosing and appearance of the drug in the serum (0.8 +/- 0.2 and 0.6 +/- 0.1 h for V and D, respectively), or in the time needed to attain the peak concentrations (4.5 +/- 0.8 and 4.1 +/- 0.9 h for V and D, respectively). The two products, however, varied in the peak serum concentration (736 +/- 125 and 536 +/- 63 ng.ml-1 for V and D, respectively), but this difference was not statistically significance. In terms of the extent of absorption, assessed by estimating the area under the concentration-time curve over 12 h, the two products were not significantly different (3,340 +/- 270 and 3,045 +/- 294 ng.h.ml-1 for V and D, respectively). These in vitro and in vivo findings indicate that Diclogesic is characterized by sustained-release properties which are comparable to Voltaren.