Biyu San: Jade-Blue Powder to Clear Heat, Drain Dampness, and Promote Diuresis
Biyu San comes from Xuan Ming Fang Lun (Discussion of Xuanshi's Formulas). It consists of Huashi (talc) 6 liang (180 g), Gancao (licorice) 1 liang, and Qingdai (indigo naturalis, enough to give the powder a bluish-green color). Powder finely. Each time take 3 qian (9 g) of Biyu San, mixed with a little honey in warm water (honey may be omitted), three times daily. Those who prefer cold drinks may mix it with freshly drawn well water (modern: chilled water).
Biyu San clears heat and drains dampness. It treats fever with vomiting and diarrhea, red-white dysentery, and dysuria with dribbling. Today Biyu San is also used for chronic arsenic poisoning and mumps. The famous anti-cancer physician Sun Bingyan, who treated tumors with relatively toxic medicinals, often drew on the rationale of Biyu San, using talc and licorice to moderate the toxicity of the poisonous drugs he used.
Biyu San is made by adding qingdai to Liu Yi San (Six-One Powder, so named because talc and licorice are combined in a 6:1 ratio). Liu Yi San is a summer formula that clears summerheat and drains dampness; it has a strong diuretic and heat-clearing action. In it talc clears heat and promotes urination, while licorice clears heat and detoxifies and harmonizes the middle; hence it is commonly used for summerheat complicated by dampness, and applied externally for prickly heat. Adding qingdai, which clears heat and drains fire, cools blood and eliminates macules, strengthens the heat-clearing power.
Both Liu Yi San and Biyu San have some antidiarrheal and antidysenteric action, and Biyu San's is the more marked. The main symptom of arsenic poisoning is vomiting and diarrhea, so Biyu San fits arsenic poisoning well. Besides arsenic poisoning, cantharidin poisoning can also be treated with Biyu San. After taking the Chinese medicinal banmao (cantharis), abnormal urination is common; cantharis also irritates blood vessels considerably, and in a few patients a rash appears after cantharis poisoning, for which Biyu San is well suited. However, rather than handling poisoning after the fact, it is better to prevent cantharidin poisoning while medicating: along with cantharis or cantharis products, take a small amount of Biyu San to prevent cantharis poisoning or cumulative toxicity.
Difficulty urinating (dysuria, lin zheng) in summer is often caused by acute urethral inflammation from various pathogens; such diseases can also be treated with Biyu San. But the talc in Biyu San has carcinogenic potential with prolonged use, so it should not be taken long-term; patients should stop once symptoms ease.