Purgative prescriptions refer to those that are mainly composed of purgatives with the therapeutic effects of relieving constipation, purging away heat, evacuating retention, and eliminating retained fluid, and used in the treatment of interior syndrome of excess type.
 
Interior syndrome of excess type may be caused either by the accumulation of heat, or cold, or dryness or fluid, and the human body may differ in the state of healthy qi as being excessive or deficient. Therefore, purgative prescriptions can be subdivided into five categories: purgative prescriptions of cold nature, purgative prescriptions of warm nature, laxatives, prescriptions for eliminating retained fluid and prescriptions for both reinforcement and elimination.
 
Purgative prescriptions of cold nature mainly consist of cathartics of cold nature with the effect of purging away heat accumulation and are applied in the treatment of excess syndrome of interior heat. Purgative prescriptions of warm nature are usually made up of Dahuang (Radix et Rhizoma Rhei) in compatibility with drugs capable of warming the interior, which purge away the accumulated cold and are used in treating excess syndrome of dyspepsia due to interior cold. Laxatives, with the function of relaxing the bowels to relieve constipation, are composed of mild cathartics and applied in the treatment of constipation due to intestinal dryness induced by deficiency of body fluid.

Prescriptions for eliminating retained fluid chiefly consist of drastic purgatives capable of eliminating retention and are employed in treating excess syndrome of excessive fluid in the body. Prescriptions for both reinforcement and elimination mainly consist of cathartics in compatibility with tonic or restorative drugs. They are expected to achieve the purpose of both purging away the excessive accumulation of pathogenic factor and restoring body resistance and applied in the treatment of excess syndrome of yangming-fu organ with deficiency of the healthy qi.
 
Purgative prescriptions are likely to impair the middle-energizer, consume body fluid, affect blood flow and cause abortion, and thus should be abandoned immediately when they achieve the expected results. It should be applied with great caution or contraindicated in the aged, the weak, those with blood deficiency from constitutional weakness or after illness, or women during menstruation or pregnancy.