Acetaminophen absorption for gastric emptying revisited.

The acetaminophen (paracetamol) absorption technique was a popular method for evaluating gastric emptying. However, it has been losing its popularity lately, as convenient 13C breath testing has rapidly become the prevailing method. There are three likely reasons for its declining popularity: 1) the acetaminophen test is indicated only for liquid emptying studies; 2) the optimal parameter for application as an emptying index remains undetermined; 3) it seems invasive and time-consuming because of the need for repeated blood sampling over several hours. We have critically reviewed the three objections in defense of the acetaminophen absorption test. Our replies to each objection are as follows: 1) liquid gastric emptying studies still have additional value to solid studies; 2) pharmacokinetic theories ensure that the peak concentration, time to peak, and area under the time-concentration curve reflect the rate of acetaminophen absorption, namely gastric emptying, with the time to peak possibly being the most accurate measure; 3) the acetaminophen absorption technique can be noninvasively performed using saliva samples. Moreover, the use of a fixed-time concentration, which is correlated with scintigraphy, could make the acetaminophen test time-saving and minimally invasive. We have claimed that acetaminophen absorption is still useful and has the potential to be a convenient gastric emptying test at community clinics and hospitals where a 13C breath analyzer is unavailable.