Laxative is a kind of medicine to promote defecation by promoting intestinal peristalsis, increasing intestinal content, lubricating intestine and softening feces. Mainly used for intestinal constipation or eliminating intestinal toxins and decomposition products. According to its functional characteristics, it is divided into the following categories:

(1) Irritant laxatives: directly acting on intestinal mucosa, making intestinal peristalsis stronger, leading to diarrhea, such as rhubarb, leaves, castor oil, etc.

(2) Volumetric laxatives: also known as salt laxatives, are sodium sulfate and magnesium sulfate that are not easily absorbed by the intestinal wall. With their help, hypertonic saline solution is formed in the intestine, which prevents the intestine from absorbing water, increases the intestinal internal volume, produces mechanical stimulation, promotes intestinal peristalsis and causes diarrhea.

(3) Lubricating laxatives: It can lubricate the intestine and intestinal contents, accelerate the backward movement of feces and cause defecation, such as liquid paraffin, vegetable oil and animal oil.

(4) Neurolaxatives: Some cholinergic drugs, such as carbamoyl choline, pilocarpine and neostigmine, can also promote intestinal peristalsis, strengthen secretion and cause diarrhea.