Antipyrine absorption after delayed oesophageal capsule transit.

Twenty fasted patients were given hard gelatin capsules containing antipyrine and barium, and in ten patients the capsule arrested and disintegrated in the oesophagus. Plasma antipyrine was assayed at 10 min intervals for 1 h, then 30 min intervals for a further 3 h. The plasma concentration-time curves for the patients in whom the capsule entered the stomach rapidly, and for those in whom the capsule lodged in the oesophagus, were compared. The absorption in the first hour was calculated from the area under the plasma concentration-time curve and found to be significantly lower if the capsule disintegrated in the oesophagus (P less than 0.0005). The time to peak plasma concentration was delayed by an average of 46 min (P less than 0.01) and the peak plasma concentration was significantly lower (P less than 0.05) if delayed capsule transit occurred. Delayed capsule transit through the oesophagus significantly changed the pharmacokinetic profile of antipyrine.