Effect of whole bowel irrigation on the pharmacokinetics of an acetaminophen formulation and progression of radiopaque markers through the gastrointestinal tract

Study objectives We describe the effects of whole bowel irrigation on a delayed-release acetaminophen preparation. We compare the mechanical effect of whole bowel irrigation on the progression of radiopaque markers through the gastrointestinal tract between an experimental and a control group. Methods We performed a 2-armed, prospective, randomized, crossover volunteer study. In the experimental phase, subjects were administered a delayed-release acetaminophen preparation (75 mg/kg) along with a capsule containing radiopaque markers. We initiated whole bowel irrigation at 30 minutes after ingestion and continued until the rectal effluent was clear. Serum acetaminophen concentrations were measured at baseline and from 0.5 to 8 hours. Abdominal radiographs were obtained at the completion of whole bowel irrigation. In the control phase, whole bowel irrigation was not performed. The primary outcome measure was the effect on the area under the acetaminophen concentration versus time curve (AUC) between the 2 groups. Results Ten subjects participated in the study. We found an 11.5% reduction in the AUC, with the majority of the effect occurring in the delayed-release portion of the curve after the 2-hour mark. This reduction, however, was not statistically significant. Radiographs obtained at the end of whole bowel irrigation revealed radiopaque markers sequestered in the right hemicolon in 8 of 10 subjects. No discernible pattern was noted in the control arm. Conclusion The effect of whole bowel irrigation on reduction of AUC for delayed-release acetaminophen preparation was not statistically significant. Whole bowel irrigation did appear to have a mechanical effect on the progression of radiopaque markers through the gastrointestinal tract, but the clinical significance of this finding is not clear.