[Relative bioavailability of paracetamol from tablets and suppositories as well as of paracetamol and codeine in a combination tablet].

Eight healthy male volunteers took part in this study to determine the relative bioavailability of Treuphadol oblong tablets (500 mg paracetamol), Treuphadol Plus oblong tablets (500 mg paracetamol, 30 mg codeine phosphate) and Treuphadol suppositories (750 mg paracetamol) against commercial tablets (500 mg paracetamol). Plasma levels of paracetamol and codeine, plus saliva levels of paracetamol for the two paracetamol only formulations, were determined by HPLC and the pharmacokinetic parameters established. The AUC data for paracetamol showed that all four preparations were bioequivalent. The saliva levels of paracetamol demonstrated a good correlation to the corresponding plasma levels. The pharmacokinetic data of codeine from the Treuphadol Plus tablet were compared with corresponding data from the literature. The bioequivalence of codeine when based on this comparison can also be assured.