Kansui Root Classic Formulas … Natural Herb Library

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Drastically drives out retained water ... Gan Sui is one of the strongest harsh purgatives in Chinese medicine and is reserved for severe edema, ascites, or stubborn chest and abdominal fluid retention.
Expels phlegm and thin-fluid accumulation ... it is used when congested water and phlegm obstruct the Lung, producing fullness, wheezing, or pronounced retained-fluid patterns that milder draining herbs will not move.
Breaks through severe excess accumulation ... classical use emphasizes short-term attack on repletion patterns, not routine use for ordinary puffiness or chronic weakness.

Shi Zao Tang ... classic severe water-retention formula in which Gan Sui is paired with Da Ji and Yuan Hua for fluid lodged above the diaphragm.
Gan Sui Ban Xia Tang ... classic phlegm-fluid accumulation strategy when stubborn retained fluids obstruct the chest or epigastrium.
Short-course purgative pairings using vinegar-processed material or moderating ingredients such as da zao ... traditional attempts to preserve action while reducing harshness.

Materia medica places Gan Sui among the strongest water-draining and phlegm-expelling toxic herbs, appropriate only for true excess accumulation.
Its traditional reputation depends as much on correct pattern selection and processing as on the herb itself.