O'Reilly R A
Arch Intern Med. 1984 May;144(5):989-91.
Cimetidine potentiates the anticoagulant effect of warfarin sodium, but in one small study ranitidine hydrochloride did not. Furthermore, these drugs have not been compared in the same subjects. Eleven normal subjects received single oral doses of 1.5 mg/kg racemic warfarin sodium alone, with cimetidine (1,200 mg/day orally), or with ranitidine (300 mg/day orally), beginning three days before the warfarin and daily thereafter for the duration of hypoprothrombinemia. Blood samples were obtained daily for determination of prothrombin times and warfarin concentrations. Cimetidine augmented both the hypoprothrombinemia and the blood concentrations of warfarin, but ranitidine did not. Substituted imidazoles like cimetidine inhibit hepatic microsomal activity, which may cause reduced metabolic clearance of warfarin and augment its anticoagulant effect. Ranitidine, lacking these effects, may be safer for patients undergoing anticoagulation who require H2-receptor antagonists.
西咪替丁可增强华法林钠的抗凝作用，但在一项小型研究中，盐酸雷尼替丁却没有这种作用。此外，尚未在同一受试者中对这些药物进行比较。11名正常受试者单独口服1.5mg/kg消旋华法林钠，或在服用华法林前三天开始每日口服西咪替丁（1200mg/天）或雷尼替丁（300mg/天），并在低凝血酶原血症期间每日服用。每天采集血样以测定凝血酶原时间和华法林浓度。西咪替丁增强了低凝血酶原血症和华法林的血药浓度，但雷尼替丁没有。像西咪替丁这样的取代咪唑类药物会抑制肝微粒体活性，这可能导致华法林的代谢清除率降低并增强其抗凝作用。雷尼替丁没有这些作用，对于需要H2受体拮抗剂的抗凝患者可能更安全。
