Effect of delayed esophageal transit on acetaminophen absorption.

Twenty patients awaiting cardiac catheterization swallowed a single tablet containing acetaminophen and barium sulfate. The first 11 subjects swallowed the tablet while supine; its progress down the esophagus was followed by fluoroscopy. In 10 of these subjects, transit of the tablet was delayed in the esophagus. The other nine subjects swallowed the tablet while standing; it entered the stomach immediately. The plasma concentration profile of acetaminophen was measured in all subjects. When there was delayed esophageal transit of tablets, the initial absorption of acetaminophen (measured as the AUC over the first 60 min) was lower than that after normal esophageal transit of tablets. The peak plasma acetaminophen concentration was also lower and occurred on average 70 min later when transit was delayed. These kinetic changes decrease the effectiveness of acetaminophen as an analgesic. We recommend that, to ensure rapid and complete drug absorption, patients be advised to swallow tablets with a large amount of water while standing.