Montelukast is an antidiarrheal medicine that is taken between meals. In comparison, it is more effective when taken one hour before a meal than half an hour before a meal, so it is usually chosen to be taken one hour before a meal. Montelukast can be used for acute and chronic diarrhea in adults and children. Its main component is silica-aluminate, and the reason for choosing to take it 1 hour before meals is that the gastrointestinal tract is relatively empty at this time, so the drug can effectively contact with the intestinal mucosa and adsorb the lost fluid from the stomach and intestines, playing a role in stopping diarrhea. In addition, it has the effect of local pain relief, repairing the damaged mucosa and balancing the intestinal flora. If taken after a meal, or half an hour before a meal, it may cause the drug and food to mix together, forming a film that is not easily digestible, affecting the efficacy of the drug and possibly causing constipation at the same time. In addition, patients also need to be aware of the need to correct dehydration while using the medication. If constipation occurs, the amount of medication can be reduced. If the diarrhea continues to worsen, promptly consult the gastroenterology department to clarify the condition and provide symptomatic treatment.