The effect of aspirin and smoking on urinary excretion profiles of lactulose and mannitol in young women: toward a dynamic, aspirin augmented, test of gut mucosal permeability

Background We explored the temporal dynamics of the lactulose mannitol test and the influence of a single dose of aspirin. Methods Twenty healthy female volunteers each received 600 mg aspirin or placebo in random sequence and were subsequently dosed with 10 g lactulose and 5 g mannitol, their urine collected every half hour for 6 h. Key Results The lactulose:mannitol ratios (LMR) of urine samples collected over the entire 6‐h period were significantly higher than those collected in the first 3 h. Greater quantities of mannitol were excreted over the first than the subsequent 3 h. A similar pattern of temporal variation in mannitol excretion was found in smokers and non‐smokers and was maintained following administration of a single 600 mg dose of aspirin. The rates at which lactulose was excreted were relatively constant over the entire 6 h period of collection, but mean levels were increased over the entire 6 h following the administration of aspirin. The effect of aspirin did not differ significantly between smokers and non‐smokers. Conclusions & Inferences While the LMR test is sufficiently sensitive to reproducibly detect the increase in intestinal permeability resulting from a single 600 mg oral dose of aspirin, the temporal patterns of excretion of mannitol and lactulose differ both in the presence and absence of aspirin. Hence, variation in sampling period and in method of dosage are likely to influence the result and it is preferable to examine the patterns of absorption of component sugars separately with due regard to the method of dosage.