In Vivo Study on Site of Action of Sinapine Thiocyanate following Acupoint Herbal Patching

OBJECTIVE: To investigate the site of action of sinapine thiocyanate (ST), following acupoint herbal patching (AHP). METHODS: Twenty Wistar rats were randomized into five groups (groups A, B, C, D, and E), and all groups received the same AHP in vivo. Skin samples were excised at 2 h, 4 h, 6 h, 10 h, and 26 h after AHP administration from group A to group E separately and the concentrations of ST in the skin were determined using a liquid chromatography-mass spectrometry/mass spectrometry (LC-MS/MS) method. A pharmacokinetic profile of ST following AHP was performed at the same time in a group of five Wistar rats to detect plasma levels at the same time intervals. RESULTS: The mean ± SD ST concentrations (ng/ml) at 2 h (group A), 4 h (group B), 6 h (group C), 10 h (group D), and 26 h (group E) after AHP administration were 250.01 ± 61.99, 61.01 ± 30.41, 40.12 ± 26.94, 78.66 ± 59.43, and 19.55 ± 18.95, respectively. No ST was detected in rats' plasma samples at the same time points. CONCLUSIONS: The site of action of ST following AHP is in the skin.