Objective: The present study was done to investigate the effect of food on the bioavailability of diprafenone.
Methods: The most important pharmacokinetic parameters (Cmax, t1/2, AUC) and the relative oral availability of a solid oral preparation of racemic diprafenone were investigated when administered to fasting subjects and 10 min after a standard meal, in an open, randomised, crossover trial. Single oral doses of 100 mg were given on two different occasions, at least 1 week apart. The serum concentrations of diprafenone and its hydroxy-metabolite were determined up to 24 hours after administration by a sensitive, specific HPLC method. Fifteen healthy, male volunteers were enrolled in the trial. Their mean height, weight and age were 183 cm, 80 kg and 22 years, respectively. Fourteen volunteers were found to be rapid hydroxylators and one was a slow hydroxylator of debrisoquine. Only data from the rapid hydroxylators were used in the statistical analysis.
Results: Food increased the oral bioavailability of diprafenone by approximately 50%. This effect was similar in rapid and in slow hydroxylators. The only slow hydroxylator in this trial had an AUCzero-last ratio (with food/fasting) of 1.54. These findings suggest that diprafenone should be administered in a constant temporal relationship to food.