Warfarin with proton pump inhibitors

Il.b.l.1. Adverse effects of anti-secretory treatment. Histamine H2 antagonists and proton pump inhibitors are very safe as well as effective treatments. Cimetidine has small effects on hepatic drug metabolism which are only of clinical signiflcance with drugs used in doses close to toxic levels, notably phenytoin, aminophylline and warfarin. Other adverse effects such as headache, rash and thrombocytopenia are rare. 

ANTICOAGULANTS-ORAL PROTON PUMP INHIBITORS Possibly t anticoagulant effect when esomeprazole, lansoprazole or omeprazole is added to warfarin Uncertain at present. Omeprazole and lansoprazole are known to induce CYP1A2, which plays a role in activation of coumarins Monitor INR more closely. 1 dose may be required. If 10%, 20% or 30% over range, omit dose for 1, 2 or 3 days respectively consider i maintenance dose by 10%. Regular dosing of a proton pump inhibitor is preferable if affects INR significantly. Not reported with pantoprazole or rabeprazole... 

Omeprazole is a proton pump inhibitor. Headache, skin rash, and diarrhea have all been recorded by adverse event registries sufficiently often to suggest causal relations (1). Omeprazole is a modest inhibitor of CYP isoforms. Interactions are less likely than with cimetidine and are probably of no practical importance. However, omeprazole reduces the absorption of drugs that require a low gastric pH (ketoconazole, iron salts, ampicilhn) and can inhibit the hepatic clearance of some drugs (diazepam, warfarin, phenytoin) (2). 

Hata M, Hayasaka M, Sezai A, Niino T, Yoda M, Unosawa S, Taoka M, Osaka S, Furukawa N, Kimura H, Minami K. Proton pump inhibitors may increase the risk of delayed bleeding complications after open heart surgery if used concomitantly with warfarin. Thorac Cardiovasc Surg 2008 56(5) 274-7. 

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