Bioavailability of diclofenac sodium: comparison of rectal suppositories with oral suspension in rabbits

Compressed rectal suppositories which are suitable and stable in tropical climates were formulated using diclofenac sodium, a potent NSAID, in polyethylene glycol 4000 base. These suppositories were evaluated for pharmacokinetic performance in rabbits at the dose of 10 mg/kg and the results were compared with those obtained after oral administration. A computer programme using model independent formulae was used to calculate different pharmacokinetic parameters. There was no difference in pharmacokinetic parameters such as Cmax, AUC0-(, t1/2 and the mean residence time (MRT) between oral and rectal formulations. But tmax was faster in case of oral administration (0.58n 0.08 h vs 1.08n 0.15 h, P < 0.05) indicating quicker drug absorption from oral suspension. Relative rectal bioavailability was 98.35n 3.58% which indicates comparable pharmacokinetic performance of rectal suppositories of diclofenac sodium in rabbits.