A pharmacokinetic study investigating the rate of absorption of a 500 mg dose of a rapidly absorbed paracetamol tablet and a standard paracetamol tablet

Objective: A rapidly absorbed tablet formulation of paracetamol containing sodium bicarbonate ( PS) has been previously shown to be absorbed at least twice as fast as a standard paracetamol tablet ( P) at a 1 g dose. In South America and Asia it is customary for patients to take a 500 mg dose of analgesic. The objective of this pharmacokinetic study was to compare the rate of absorption of PS versus P at a 500 mg dose. Research design and methods: An open, randomized, single dose, cross-over study. Thirty Hispanic healthy volunteers randomly received a 500 mg dose taken orally with 50 mL of water 2 h after a standard breakfast. Blood samples were taken up to 10 h post-dose. Plasma concentrations of paracetamol were determined by HPLC with UV detection. Main outcome measures: AUC(0-30min), C-plasma30min and T-max were analyzed non-parametrically by the Wilcoxon's rank sum test. A linear mixed effects model was used to analyze the logarithmically transformed AUC(0-proportional to), and C-max. Bioequivalence. was accepted if the 90% confidence intervals ( CI) for the ratio of the means of the primary pharmacokinetic variable AUC(0-proportional to) lay completely within the range 0.80 - 1.25. Results: AUC(0-30min) and C-plasma30min were significantly greater and Tmax was significantly shorter ( all p < 0.0001) for PS versus P. The formulations were bioequivalent for AUC(0-proportional to) ( 90% CI 0.99: 1.05) and no statistical difference was seen for Cmax ( 95% CI 0.91: 1.14). Conclusions: Paracetamol was absorbed at least twice as fast from PS compared to P at a 500 mg dose. The extent of absorption was equivalent for both formulations.