Warfarin is a very important drug that is often applied after cardiac surgery. It has an anticoagulant effect and is used to prevent the formation of blood clots in the human body. Under normal conditions, blood flows smoothly and continuously through the heart and blood vessels, and everywhere it touches is covered by a layer of endothelial cells. When any of these three “no’s” occur, the clotting process is activated and a thrombus is formed. After cardiovascular surgery, direct contact of foreign valves with blood, trauma, exposure of tissue without endothelial cell coverage in the lumen of the vessel or in the heart, and slow local blood flow due to atrial fibrillation resulting in vortex formation can all lead to thrombosis in the heart or blood vessels. Symptoms of warfarin overdose: a wide variety of bleeding manifestations. Symptoms of bleeding, such as persistent wound bleeding, hemoptysis, vomiting blood, black stools, hematuria, nosebleeds, bleeding gums, hematomas, bruising under the skin, hemiplegia or coma (cerebral hemorrhage), should be seen immediately regardless of the INR value. Effect of food on warfarin: Multivitamin preparations containing vitamin K that are used as supplements (Sun Cun, Schercon, etc.) can antagonize the anticoagulant effect of warfarin. The administration of these preparations leads to a high dosage of warfarin in patients, and the INR rises rapidly to dangerous levels when they are discontinued. Green tea, soy milk, pork liver, spinach, cauliflower, avocados, ginseng, American ginseng, and foods containing seaweed also diminish the effect of warfarin leading to blood clots; in addition, mangoes, fish oil, grapefruit, cranberries, salvia, turtle berry, garlic, and papaya can enhance the anticoagulant effect of warfarin. The effect of drugs on warfarin: a class of drugs that can enhance the anticoagulant effect of warfarin, the most common of which is acetaminophen, including Neocontrol, Tylenol, etc., is commonly used to alleviate the symptoms of colds, and many cold medicines contain such ingredients. Therefore, patients taking warfarin should use these drugs or compounded preparations containing such ingredients with caution when they have a cold. Aspirin, a drug commonly used by heart patients, can enhance the anticoagulant effect of warfarin. Broad-spectrum antibiotics can enhance the anticoagulant effect of warfarin. Among the commonly used cardiovascular drugs, diltiazem (Hersinol), etanercept (cortolone) and statin lipid-lowering drugs increase the anticoagulant effect of warfarin. The antifungal drug fluconazole can also enhance the anticoagulant effect of warfarin. The second group of drugs that can diminish the anticoagulant effect of warfarin is less common, except for preparations containing vitamin K. Commonly used are ribavirin, rifampin, abciximide, carbamazepine, barbiturates, and mesalazine. In conclusion, the instructions of other drugs should be read carefully before taking them and, if needed, the INR should be tested repeatedly during the course of administration to avoid undetected changes in anticoagulation strength brought about by drug interactions.