Dǎohuàn Sàn (Rearrangement Powder) 倒換散

From the section on Urinary Stoppage in the Yī Fāng Kǎo (Analysing Medical Formulas) by Wu Kun, 1584 CE. 《醫方考·小便不通門第三十八》

大黃（一兩）荊芥（二兩）
dà huáng (1 liǎng) Jīngjiè (2 liǎng)

每服末二錢。
Every dose take 2 qián [of the powder].

內熱小便不通者，此方主之。
For those with internal heat and urinary stoppage,[1] this formula governs it.

內熱而小便不通者，鬱其少火，而氣不化也。《內經》曰∶膀胱者，州都之官，津液藏焉，氣化則能出矣。然化氣之道，莫妙於升降。天地以升而降化萬物，奈何而昧於人乎？
For those with internal heat that leads to urinary stoppage, this is depression of the lesser fire, and then qì cannot transform. The Nèijīng says the bladder, it is the official of provinces and cities, the jīnyè-fluids are stored within it; with qì transformation, it (jinyè-fluids) can emanate. And for the dào (principle/natural law) of this qì transformation, there is nothing more marvelous than the [movements] of ascending and descending. Heavens and earth, by ascending and descending, are able to transform the ten-thousand things. How can people be ignorant of this?

故用荊芥之輕清者以升其陽。用大黃之重濁者以降其陰。清陽既出上竅，則濁陰自歸下竅，而小便隨泄矣。方名倒換者，小便不通，倍用荊芥。大便不通，倍用大黃。顛倒而用，故曰倒換。
Thus, by utilising the light and clear [nature] of jīngjiè, it can raise the yáng. By utilising the heavy and turbid [nature] of dàhuáng, it can descend the yīn. Once the yáng exits via the upper orifices, the turbid yīn will naturally return to the lower orifices, and then urination will be discharged subsequently.

For the name of the formula name, Dǎohuàn (Rearranging), when urination is stopped, double the dosage of jīngjiè; when there is constipation, double the dosage of the dàhuáng; [the dosage] can be reverted in use,, therefore it is called Rearrangement [Powder].

Thanks to Allen Tsaur and Will Ceurvels for their help, and Mark Gearing for picking up an error in the dosages.

[1] According to the Practical Dictionary “this is either dribbling urination or complete blockage in severe cases.”

[2] From Suwen Chapter 5.