Further evidence for the influence of intraduodenal pH on the PABA test

The effect of prior administration of 400 mg of cimetidine on the outcome of the PABA test was investigated. In 8 patients the PABA test result rose with on average 27.5% after the administration of cimetidine. Four of them were selected for these investigations, because a much lower PABA test result had been obtained than was expected from the Lundh test result. In one patient, the low PABA test result was in conflict with faecal fat excretion and the clinical condition. Three patients were selected with severe pancreatic dysfunction, as demonstrated by the PABA test, Lundh test and faecal fat excretion. The change effected by cimetidine was shown to be significantly related to duodenal pH and mean trypsin activity as measured in the Lundh test. In a control group of four patients with a PABA test result in the normal range, no significant effect of cimetidine administration was seen. The beneficial effect of cimetidine can be explained by its known inhibiting influence on gastric acid production, resulting in higher intraduodenal pH with subsequent enhanced enzymatic activity. The importance of intraduodenal pH for the PABA test result is further stressed by these results.