Montelukast is an antidiarrheal drug, which is not easily absorbed by the intestine and can be attached to the intestine to achieve antidiarrheal effect, and can be used clinically to treat pediatric diarrhea. However, since the dosage is difficult to grasp and not all pediatric diarrhea is suitable, it is recommended to use montelukast cautiously in the following cases: 1. If a child has diarrhea but does not have frequent stool symptoms, there is no need to use montelukast for treatment. This is because montelukast mainly relies on strong water absorption to achieve the antidiarrheal effect of reducing stool frequency and changing stool properties, while children whose stool frequency has not increased significantly may induce constipation after taking montelukast as a side effect. This may cause the bacteria to stay in the intestinal tract for a long time and toxins to accumulate, which is not conducive to physical recovery. Usually, if a child has diarrhea, such as change in stool characteristics or increase in the number of times, it is recommended to consult a doctor promptly and listen to the advice of the treating physician if montelukast is needed.