Essential medicines for adult diarrhea include Montelukast, Loperamide and Bifidobacterium capsules. 1. Montelukast: It is a kind of antidiarrheal agent, which forms a protective layer in the intestinal tract and can play a protective role for the intestinal mucosa after taking it. It is usually used for acute diarrhea caused by intestinal infections, or chronic diarrhea caused by intestinal malabsorption. But this drug should be used together with the treatment of the original disease, the effect is better. 2. Loperamide: It is mainly used for acute or chronic diarrhea of non-intestinal infections. Its effect is mainly to reduce the peristalsis of the intestinal tract, increase intestinal operation, and at the same time make the anal sphincter tightly closed to prevent diarrhea and fecal incontinence. 3. Bifidobacterium capsule: it is a kind of probiotics, which can adjust the intestinal flora, usually used for the treatment of dyspepsia or irregular diet and other causes of physiological diarrhea, patients need to ensure that the regular diet at the same time taking this drug. All of the above drugs should be used under the guidance of clinicians, do not self-medication.