The dependence of paracetamol absorption on the rate of gastric emptying.

1. The rate of gastric emptying was measured directly in 14 convalescent hospital patients and paracetamol absorption was studied following an oral dose of 1.5 g.2. Rapid gastric emptying was associated with the early appearance of high peak plasma paracetamol concentrations whereas peak concentrations were low and occurred late when gastric emptying was slow.3. There was a significant correlation between the rate of gastric emptying and the 0-4 and 0-24 h urinary excretion of paracetamol and its metabolites.4. In five patients with abnormally slow gastric emptying the mean maximum plasma concentration and 0-4 and 0-24 h urinary excretion of paracetamol were significantly lower than in seven patients with normal gastric emptying rates while the time taken to reach maximum plasma concentrations was longer.5. Individual differences in the rate of gastric emptying may contribute to variable absorption of many drugs.