The Medicinal Value of Mirabilite (Mang Xiao)
Mirabilite (Mang Xiao) is a mineral used in TCM from ancient times to the present; its main component is sodium sulfate. Among the sulfates, both sodium sulfate and magnesium sulfate are excellent laxatives. Their purgative mechanism is that the sulfate ions they contain are poorly absorbed by the intestine, forming a hypertonic saline solution in the gut that retains large amounts of water, distending the bowel, producing mechanical stimulation, and promoting peristalsis. In addition, sulfates exert a chemical irritation on the intestinal mucosa but do not damage it, so clinically they are used as laxatives. In modern medicine, the day before a colonoscopy, patients are often given a day of magnesium sulfate or sodium sulfate to empty the bowel for the examination.However, magnesium sulfate has side effects in patients poisoned by central-nervous depressants or with impaired renal function; for such patients, Mirabilite is preferable to magnesium sulfate for catharsis. But Mirabilite also has some toxicity: the intraperitoneal LD50 of Mirabilite decoction in mice is 6.738 g/kg. Poisoning incidents with Mirabilite are not uncommon: Hu Wanlin once had people drink large amounts of Mirabilite water, causing a young man's sudden death, for which he was sentenced a second time.Besides internal use, Mirabilite can be applied externally. For infected wounds, a 10%–25% sodium sulfate compress reduces swelling and pain through its hyperosmotic effect. TCM also often applies Mirabilite externally on the navel to promote diuresis and bowel movement. Mirabilite can also be held in the mouth in small amounts; for esophageal-cancer patients who cannot eat, holding Mirabilite in the mouth can slightly relieve symptoms, though the effect does not last. Decocting Mirabilite and Coptis (Huang Lian) together and washing the affected area treats red, swollen, itchy skin.TCM holds that Mirabilite purges and frees the bowels, softens hardness and dissipates nodules, and clears fire and reduces swelling. It is one of the common TCM medicines for constipation. Both Da Chengqi Tang and Xiao Chengqi Tang use Mirabilite; constipated patients easily become irritable and "heat up," so TCM also uses Mirabilite to eliminate vexation and drain fire. Psychiatric patients with manic reactions are often constipated—especially those with depression, bipolar disorder, and schizophrenia, who usually have constipation during episodes. Mirabilite is therefore used fairly often in treating such illnesses; for these patients, Da Chengqi Tang, Xiao Chengqi Tang, and Zengye Chengqi Tang containing Mirabilite can relieve the manic state and constipation during episodes.Tumor patients also commonly have constipation, so oncologists use Mirabilite and rhubarb (Da Huang) and other purgatives fairly often. Many oncologists use Mirabilite and rhubarb to excrete various necrotic tissues and wastes produced by the tumor, so Mirabilite appears frequently in purgative (xia fa) formulas used to treat tumors.Mirabilite and borneol (Bing Pian) in a 10:1 ratio, made into a powder for external use, give good anti-inflammatory and analgesic effects and can be used for acute mastitis, cellulitis, lymphangitis, and phlebitis, and as a compress for burns and scalds. Bingpeng San, made from Mirabilite, borax (Peng Sha), and borneol, is a Chinese patent medicine available in pharmacies; it is used for red, swollen, painful eyes, sore throat, mouth ulcers, intestinal abscess, breast abscess, and erysipelas.After efflorescence, Mirabilite becomes a powdery solid; this powder is called Xuanming Fen, with effects essentially equal to Mirabilite. Neither Mirabilite nor Xuanming Fen needs to be decocted; after the other herbs are cooked, they are poured into the decoction and dissolved directly for ingestion. The usual dose of Mirabilite is 10–30 g. Those with weak spleen and stomach, loose stools, and pregnant women should not use Mirabilite.