Effect of Food on the Multiple-Peak Behavior After a Single Oral Dose of Diclofenac Sodium Slow-Release Tablet in Humans

Abstract

This study evaluated the effect of a standard meal on the multiple-peak behavior of diclofenac sodium following oral administration of a 100-mg slow-release (SR) wax-matrix tablet. The study was a randomized, 3 × 3 Latin-square trial balanced for residual effects, in which 18 subjects were randomly assigned to treatment sequences consisting of three treatments: (A) one 100-mg SR tablet, fasted; (B) one 100-mg SR tablet, fed; and (C) 100-mg diclofenac sodium buffered aqueous solution, fasted. Blood samples were obtained over a 24-h period for Treatments A and B, and over an 8-h period for Treatment C. Food did not significantly affect the extent of absorption but generally delayed the onset of absorption from the SR tablet. The plasma concentration-time profile for the SR tablet under fasted conditions was characterized by multiple-peak behavior. Under fed conditions, the SR tablet showed a more consistent absorption pattern, with a single peak occurring usually between 5 and 6 h. The concentration-time profile of the buffered aqueous solution showed a very rapid absorption phase followed by a rapid decline and a terminal elimination half-life of approximately 1.8 h. A single peak was observed following the buffered aqueous solution. This observation, in conjunction with evidence from other studies, leads to the conclusion that gastrointestinal pH may be responsible for the multiple-peak behavior observed following diclofenac sodium dosing. As compared to the solution, the was-matrix tablet under both fasted and fed conditions showed slow-release, characteristics.