Warfarin is one of the most important anticoagulant drugs frequently used in cardiovascular system diseases requiring anticoagulation, and how well it is used directly affects the therapeutic effect and prognosis of patients. Although it is not a serious problem such as cerebral hemorrhage or abdominal bleeding, it should be noted that many drugs can enhance or diminish the effect of warfarin, leading to thrombosis due to insufficient anticoagulation or bleeding tendency due to excessive anticoagulation, therefore, patients taking warfarin need to check INR diligently when combining other drugs. All drugs and foods that may affect the anticoagulant effect of warfarin are summarized for your reference. First, the main mechanism of interaction with warfarin (1) liver metabolism: the metabolism of warfarin in the body is mainly through the liver cytochrome P450 enzyme system, so the drugs that can inhibit CYP450 activity can slow down the metabolism of warfarin, prolong the half-life and enhance the anticoagulant effect; conversely, the drugs that can induce CYP450 activity can weaken the anticoagulant effect of warfarin. (2) Binding with plasma proteins: Warfarin binds to plasma proteins (mainly albumin) at a rate of 98% to 99%, therefore, drugs and foods with high plasma protein binding rate can competitively inhibit warfarin binding to plasma proteins, resulting in an increase in free warfarin and enhanced anticoagulant effect. Second, the interaction between warfarin and drugs (1) drugs that enhance the anticoagulant effect of warfarin ① drugs that affect the absorption of vitamin K: broad-spectrum antibiotics. (2) Drugs with high plasma protein binding rate: aspirin, sulfonamides, etc. ③Drugs that inhibit the activity of hepatic CYP450 enzyme system: macrolide antibiotics, amiodarone, allopurinol, metronidazole, etc. ④Drugs that increase the affinity of warfarin and receptors: quinidine, thyroxine, etc. ⑤Drugs that interfere with platelet function: aspirin, salicylates, etc. (2) Drugs that weaken the anticoagulant effect of warfarin ①Drugs that induce the activity of hepatic CYP450 enzyme system: phenobarbital, carbamazepine, sedative-hypnotics, etc. (2) Drugs that compete for enzyme proteins: vitamin K, oral contraceptives and estrogens, etc.