title: Warfarin dosing after bariatric surgery: a retrospective study of 10 patients previously stable on chronic warfarin therapy.
abstract: Many changes associated with bariatric surgery have the potential to affect warfarin dosing; yet current literature includes little data describing this phenomenon. Investigating this relationship may allow for determination of post-bariatric surgery warfarin dosing using stable pre-operative dosing levels. A retrospective chart review was completed for 10 patients stabilized on chronic warfarin therapy who underwent bariatric surgery. Data collection consisted of the following: warfarin requirement in mg/week, time in target range (TTR), creatinine, liver function, diarrhoea, medication changes, diet, and signs of bleeding and/or thrombosis. Three study patients underwent laparoscopic adjustable gastric banding procedures and seven patients underwent Roux-en-Y gastric bypass. The average (standard deviation) weekly warfarin dose required in the immediate post-operative interval was 64% (25%) of baseline dosing, corresponding to a TTR of 48%. At 6 months, patients required 85% (19%) of baseline weekly dosing, with TTR of 53.4%. At 1 year, dosing was 90% (16%) of baseline with TTR of 63.5%. Patients underwent medication changes as well as transient bouts of diarrhoea. Two patients suffered unspecified haemorrhages of the gastrointestinal tract (international normalized ratio [INR] = 2.3 and 9.8). This patient set demonstrated an initial drop in warfarin requirement, followed by escalating dosing trends that became more predictable as patients were farther out from procedure.
authors.affiliation: Department of Pharmacy, Methodist Hospital, St. Louis Park, MN, USA.
authors.forename: A M
authors.initials: AM
authors.lastname: Schullo-Feulner
authors.forename: Z
authors.initials: Z
authors.lastname: Stoecker
authors.forename: G A
authors.initials: GA
authors.lastname: Brown
authors.forename: J
authors.initials: J
authors.lastname: Schneider
authors.forename: T A
authors.initials: TA
authors.lastname: Jones
authors.forename: B
authors.initials: B
authors.lastname: Burnett
mesh_terms: D000328:Adult; D000925:Anticoagulants / Q000008:administration & dosage* / Q000494:pharmacology*; D050110:Bariatric Surgery; D001777:Blood Coagulation / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D014859:Warfarin / Q000008:administration & dosage* / Q000494:pharmacology*
chemical_list: D000925:Anticoagulants; D014859:Warfarin
keywords: Bariatric; INR; surgery; warfarin