Yuanhu Zhitong Tablets, a Pain-Relieving Chinese Patent Medicine
Yuanhu Zhitong Pian (Corydalis Pain-Relieving Tablets) is a modern Chinese patent medicine; its formula is recorded in Part I of the 2005 edition of the Pharmacopoeia of the People's Republic of China. Its composition is: vinegar-processed yanhusuo (Corydalis Rhizoma, also called yuanhu) 445 g, and baizhi (Angelicae Dahuricae Radix) 223 g.
Preparation: crush 166 g of the baizhi into a fine powder. Crush the remaining baizhi together with the yanhusuo into a coarse powder; macerate for 24 hours in three times the amount of 60% ethanol, then heat-reflux for 3 hours; collect the extract. Combine the two extracts, filter, and concentrate the filtrate into a thick extract. Add the fine baizhi powder above, granulate, press into 1,000 tablets, and coat with sugar film or a film coat; the tablets are ready.
Dosage: orally, three times daily, 4–6 tablets each time. Yuanhu Zhitong Pian moves qi, invigorates blood and stops pain; it is indicated for stomach pain, hypochondriac pain, headache and dysmenorrhea due to qi stagnation and blood stasis.
The yanhusuo (yuanhu) in Yuanhu Zhitong Pian is the dried rhizome of Corydalis yanhusuo, a Papaveraceae plant. Its analgesic effect reaches about 40% of morphine's, yet it is not addictive like morphine. Yanhusuo works poorly when decocted in water and better in pills or powders. Traditional TCM holds that yanhusuo must be vinegar-processed to exert its best effect; modern research finds yanhusuo is poorly soluble in water but soluble in acetic acid, so vinegar-processing indeed enhances its potency—which is also why decocting it in water works poorly. Yanhusuo softens blood vessels and has four major effects: activating blood, moving qi, stopping pain and promoting urination; it is a relatively ideal antispasmodic analgesic.
Baizhi is a diaphoretic and analgesic herb. TCM holds that baizhi is acrid in dispersing, warm in unblocking, and aromatic in opening orifices; it both releases the exterior (reduces fever) and stops pain, and opens the nasal orifices. Hence baizhi is much used for headache, supraorbital pain, bone pain and nasal congestion caused by colds and fever. Baizhi is also a common pus-expelling herb for sores and swellings: it can dissipate pus not yet formed and rupture pus already formed, so TCM external medicine uses it often.
The tablets made by combining yanhusuo and baizhi give a better analgesic effect and a wider range of indications. Yuanhu Zhitong Pian works well for stomach pain; if the patient also has excess stomach acid, note to combine it with antacids. Combining Yuanhu Zhitong Pian with Zuojin Wan works well for pain caused by reflux esophagitis or reflux gastritis.
Yuanhu Zhitong Pian can treat mild-to-moderate cancer pain, but its analgesic effect on more severe cancer pain is not ideal; severe cancer-pain patients still need to consider stronger analgesics such as OxyContin.
In treating women's dysmenorrhea, note that Yuanhu Zhitong Pian should be used cautiously when menstrual flow is heavy, because both yanhusuo and baizhi have a blood-activating effect and taking the tablets will increase bleeding.
For spasmodic pain, Yuanhu Zhitong Pian alone is less effective than combining it with Shaoyao Gancao Tang; for the latter use baishao 3 g and gancao 3 g, steeped in boiling water and drunk as a tea.