Dose dependence of the 14C-aminopyrine breath test. Intrasubject comparison of tracer and pharmacological doses.

Although the aminopyrine breath test has received much attention, the question has not yet been settled whether pharmacological or tracer doses of the drug should be used. Nine volunteers were given 14C-aminopyrine 9 mg/kg or a tracer amount, in a randomized sequence and according to a crossover design. The specific activity of 14CO2 in breath was significantly different only during the first hour. Up to the 8th hour the disappearance of 14CO2 from breath was smaller after the pharmacological (28.5 +/- SD 5.4%/h) than after the tracer dose (36.2 +/- 10.6%/h; p less than 0.05). The over-all disappearance of 14C-atoms from the subjects was significantly slower after the higher dose. In view of the smaller radiation exposure and the decreased risk of agranulocytosis, the use of a tracer dose appears preferable.