Montelukast and norfloxacin are best avoided when taken together. Montelukast is an intestinal mucosal protector that is often used to treat diarrhea, while norfloxacin is an antimicrobial drug that is clinically indicated for the treatment of gastrointestinal disorders associated with bacterial infections and kills pathogenic microorganisms. If these two drugs are taken together, montelukast tends to adsorb norfloxacin, hindering its antimicrobial effect and immobilizing and inhibiting viruses and bacteria in the digestive tract as well as some of the toxins produced, so montelukast and norfloxacin are best not taken together. If patients want to take these two drugs, it is recommended that they should consult a doctor and take them under the doctor’s supervision.