Influence of gastric emptying on the PABA test

Serum and urine PABA curves monitored in 13 healthy volunteers were analysed and compared with curves from 11 healthy volunteers after administration of the gastrokinetic agent domperidone. Both in serum and in urine less variation in the PABA curves was observed after domperidone. Results without domperidone were subdivided in a group with normal gastric emptying (I) and a group with slow gastric emptying (II), based upon the time at which the serum PABA peak was found. Maximal serum PABA concentration, serum PABA at t = 60 min, lagphase and t1/2 for urinary excretion, and % PABA excretion from 0-3 h, 3-6 h and 0-6 h differed significantly between the two groups. Instead, no differences were found between subgroup I and volunteers after concomitant domperidone administration. In summary, PABA test results in serum and urine are influenced by variations in gastric emptying. Domperidone corrects for delayed gastric emptying and thereby narrows the range of normal PABA excretion values.