Even though the herb Qu Mai 瞿麥 (Dianthus superbus) is considered “alchemically unstable,” which means it has certain hepatotoxic effects, it is in fact a very effective herb in treating water metabolic conditions such as diabetes or liver failure with underlying Yang deficiency.
Qu Mai is one of the key herbs in Trichosanthes and Dianthus Pill 瓜蔞瞿麥丸 Gualou Qumai Wan, a classical formula from the classical Chinese medical book “Jingui Yaolue” (金匱要略), Chapter 13 “Thirst, Inhibited Urination, Strangury” 消渴小便利淋病脈證治, Line 10.
The original line states that “inhibited urination means that there is water Qi and that the patient suffers from thirst. Trichosanthes and Dianthus Pill governs.” 小便不利者，有水氣，其人苦渴，瓜蔞瞿麥丸主之。
For patients with inhibited urination, unquenchable thirst, and signs of Yang deficiency, this formula has been proven to be very effective. (Do NOT prescribe any formula to anyone, including yourself, before consulting with a professionally trained practitioner.)
Some patients experience unquenchable thirst because their body is incapable of retaining water inside the cells. Imagining your arm muscles are extremely fatigued and unable to do any work. In this case, the cells are “fatigued” and incapable to hold water side. This is considered a form of “wasting thirst disorder” 消渴病 or “extreme deficiency and exhaustion disorder” 虛勞病. Such patients’ body is left dehydrated even if they constantly drink water. The water immediately leaks out from the cells into the tissues which results in severe swelling/edema. At the same time, the Kidneys are dysfunctional so that they don’t filter water properly, which leads to the symptom of inhibited urination. Such symptoms often present in patients with liver failure. The patients may also experience a sense of coldness in the abdomen and low back, which is a sign of Kidney Yang deficiency.
This formula is considered a “classic” because it is so well-constructed and elegant — while Gua Lou Gen (Trichosanthis Fructus Radix) is known for quenching thirst by generating healthy fluids, Qu Mai assists Gua Lou Gen by locking water inside the cells (locking aquaporins –water channel proteins of the cell membrane) so that the body would feel hydrated, therefore stop sending signals to the brain, screaming that it feels thirsty and needs water. Pao Fu Zi (Acotini Carmichaeli Praeparata Radix Lateralis) 炮附子 restores the warmth-generating functions of the Kidney, while Fu Ling draining the stale and stagnant fluids, and Shu Yu replenishing the healthy body fluids and moistens the dehydrated tissues.
This is an elegant yet powerful formula. I feel that it would be a shame if it is avoided in clinical practices because a lot of people can benefit from having this formula available to them.