Utility of in vitro and in vivo systems for studying the permeability of capsaicin and nonivamide through different intestinal regions.

1. The present study determined and compared the permeability of capsaicin and nonivamide along the length of the intestine in rats. Accordingly, the purpose was to evaluate this synthetic analog as a clinical substitute for capsaicin.. 2. Permeabilities of capsaicin and nonivamide were measured in experiments utilizing Ussing chambers and in vivo methods. Capsaicin concentrations were examined by liquid chromatography-tandem mass spectrometry (LC-MS/MS). 3. Both capsaicin (0.80 × 10cm/s) and nonivamide (0.22 × 10cm/s, p > 0.05) had poor permeabilities across the jejunal membrane. The permeability of nonivamide (10.12 × 10cm/s) was significantly greater than that of capsaicin (5.34 × 10cm/s, p < 0.05) across the iliac membrane. In contrast, the permeability of nonivamide (8.42 × 10cm/s) across the colonic membrane was markedly lower than that of capsaicin (14.48 × 10cm/s, p < 0.05). In accordance with the in vitro study, the drug concentration-time curve of nonivamide was significantly higher in the ileum (F = 14.18, p < 0.05) but lower in the colon (F = 11.86, p < 0.05) compared with capsaicin. 4. The results demonstrate that capsaicin and nonivamide exhibit varying permeabilities across several different intestinal tissues. The relevance of such extended investigations to healthcare is underscored by the lower cost of nonivamide versus capsaicin, along with potential application in prevention and management of the disease.