Warfarin is currently the most widely used oral anticoagulant in the world and is often used to treat or prevent thrombotic disorders such as post-valve replacement, atrial fibrillation, lower extremity venous thrombosis and pulmonary embolism. Warfarin is a double-edged sword that can prevent and treat disease when used properly, but can lead to serious and even life-threatening consequences such as cerebral hemorrhage and gastrointestinal hemorrhage if used improperly. Many prescription or over-the-counter medications can enhance or diminish the effects of warfarin. It is important for patients taking warfarin for a long time to be aware of this, so that improper use does not lead to an increased risk of bleeding or thrombotic events. So, which drugs can affect the anticoagulant effect of warfarin? Herbs that weaken the anticoagulant effect of warfarin include: ginseng, American ginseng, and St. John’s wort. Western drugs that reduce the anticoagulant effect of warfarin include: phenytoin sodium, barbiturates, oral contraceptives, estrogen, clofentezine, rifampin, vitamin K, chlorothiazide, spironolactone, corticosteroids, etc. In addition to drugs, daily diet can also play a role in the effectiveness of warfarin: for example, spinach, cabbage, leek, coriander, lettuce, celery, watercress, carrot, tomato, broccoli, cauliflower, cabbage, lettuce, green pepper, chili, garlic, onion, egg yolk, soybean oil, cod liver oil, seaweed, avocado, animal liver, black tea, green tea. All are foods that can weaken the anticoagulant effect of warfarin. Experts also warn that because the negative effects of warfarin should not be underestimated, the following matters must be noted during the administration of the drug: First, it is advisable to take the drug regularly. Patients need to take it at the same time every day (preferably before bedtime). If you forget to take the medication, you should take it within 4 hours; do not take it more than 4 hours, and take the medication normally the next day, not double the dose. Second, it is advisable to have regular checkups. The dose of warfarin varies from person to person, and the drug dose needs to be adjusted according to the coagulation function index. The PT (plasma prothrombin time) and INR (International Normalized Ratio) values in the coagulation mechanism must be monitored while taking the drug, and the INR value should be controlled at 1.8-2.5 (2.0-3.0). Monitoring needs to be done once or twice a week until the standard is reached, then smoothly changed to once every 1-2 weeks, and then once a month, with intervals generally not exceeding 3 months. If the INR does not reach the standard or exceeds the standard, you should contact your physician promptly. Third, it is advisable to have a regular diet. The mechanism of action of warfarin is to antagonize vitamin K to exert anticoagulant effect. The vitamin K content of various foods varies, so changes in the structure of the diet can affect the effect of warfarin. Vegetables rich in vitamin K, such as spinach, asparagus, green cauliflower and lettuce, may reduce the anticoagulant effect of warfarin. Therefore, you should try to maintain a balanced dietary structure, no need to deliberately favor or forbid a certain food, do not blindly change the food structure, add nutrients. Fourth, pay attention to drug interactions. The anticoagulant effect of warfarin is susceptible to drug interference. Common antibiotics such as metronidazole, azithromycin, cefoperazone and levofloxacin interfere with warfarin metabolism and enhance its anticoagulant effect. Phenytoin sodium and oral contraceptives, on the other hand, may reduce their anticoagulant effect. Therefore, it is important to inform the physician that you are taking warfarin, pay attention to drug interactions, and monitor the INR when adjusting drug therapy, and adjust the warfarin dose if necessary. For patients who are taking warfarin for other diseases requiring surgical treatment, the drug needs to be discontinued before surgery after physician evaluation, usually 5-7 days in advance, and other anticoagulants with short duration of action should be used instead of warfarin, such as normal heparin or low molecular heparin. Fifth, pay attention to adverse reactions such as bleeding. The biggest adverse reaction of warfarin is that it causes bleeding. During taking the drug, you must pay attention to any bleeding of skin mucosa, conjunctival bleeding, gum bleeding, nasal bleeding and black stool, hematuria and other conditions.