Comparative bioavailability of two enteric-coated tablet preparations of diclofenac sodium

In a random cross-over study, eight healthy volunteers received single 25 mg doses of enteric-coated diclofenac sodium tablets (as either Voltaren 25, Ciba-Geigy or Anfenax 25, Istituto Biochimico Italiano) after an overnight fast. The bioavailability of these two preparations of diclofenac sodium did not differ significantly as judged by absorption lag time, peak plasma concentration, time to peak plasma concentrations or area under the plasma concentration-time curve. Diclofenac was found to have a plasma clearance of 2.85 +/- 1.03 (s.d.) and 3.39 +/- 1.43 ml min-1 kg-1, a plasma terminal half-life of elimination of 0.61 +/- 0.25 and 0.71 +/- 0.39 h, and an apparent volume of distribution of 0.15 +/- 0.10 and 0.21 +/- 0.13 l kg-1 (the values obtained with the Ciba-Geigy preparation being shown before the Istituto Biochimico Italiano preparation in each case).