Abstract
The urinary recovery of p-aminobenzoic acid (PABA), following small intestinal hydrolysis by chymotrypsin of the synthetic peptide N-benzyl-tyrosyl-PABA (Bentiromide), provides the basis for an oral pancreatic function test. A conventional two day test repeated on a second day with PABA alone, was found to be inaccurate and of little use as a screening test for pancreatic insufficiency (PI). The test was modified in order to make it more suitable for children. 28 children with PI aged 17 mo – 16 y were studied (25 cystic fibrosis, 2 Shwachman's, 1 pancreatectomy) together with a group of 20 control patients, aged A mo - 11 y, shown to have normal pancreatic function by pancreozymin-secretin testing and faecal chymotrypsin estimation. Following an overnight fast, a pre-test urine sample was taken and then Bentiromide (15 mg/kg) with 4.5 mg/kg p-aminosalicylic acid (PAS, a structural analogue of PABA) administered with a standard breakfast of cereal and milk. A six hour urine collection was then made. After alkaline hydrolysis of PABA and PAS conjugates, urine samples were assayed by HPLC using a 300 × 3.9 mm column of u-Bondapak-C18. Results were expressed for each patient as PABA Excretion Index (PEI = urine PABA/urine PAS). The mean PEI in patients with PI was 19 (range 4-62) and for controls, 87 (range 66-140), with complete separation of values for patients with PI and control subjects, p<0.0001. Thus the use of PAS as a pharmacokinetic marker for PABA absorption and excretion in combination with Bentiromide provides a sensitive and specific 6 hour screening test for exocrine pancreatic insufficiency in children.
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