title: Interventions to improve anticoagulation with warfarin.
abstract: BACKGROUND
  This study aimed to investigate potential drug-drug interactions (pDDIs) with warfarin to minimize them, assess the acceptability of pharmaceutical interventions by the medical team and the impact on the international normalized ratio (INR) results.
  
  
  METHODS
  This pertains to a prospective study involving inpatients who started warfarin therapy in a university hospital located in southern Brazil. The pDDIs with warfarin were identified using the interaction screening program Drug-Reax, Micromedex Healthcare Series 1.0.
  
  
  RESULTS
  Two hundred and two inpatients were monitored. The mean of 10 different drugs was prescribed for each patient (SD = 3.6). At least 1 major or moderate pDDIs with warfarin per patient was observed, the mean was 3.6 (SD = 1.6). The most common pDDIs with warfarin involved in the increase of anticoagulation effect were enoxaparin (32.2%), simvastatin (27.6%), omeprazole (22.5%), and tramadol (21.5%). For 32 patients (15.8%), interventions were rejected, and they had a higher risk (relative risk= 2.17; 95% confidence interval 1.10-4.27) for abnormal test results (INR > 5). Multivariate analysis showed that age, length of hospital stay, exposure to ≥4 major or moderate pDDIs, and refusal of pharmacist recommendations contribute significantly to the patient's INR result >5. Consequently, the risk of bleeding is increased.
  
  
  CONCLUSIONS
  Major and moderate pDDIs with warfarin are very common in inpatients and are associated with INR results outside the therapeutic range. Pharmaceutical interventions concerning the management of interactions by providing information to physicians can improve the patient safety.
authors.affiliation: São Lucas University Hospital, Pontifícia Universidade Católica do Rio Grande do Sul, Departamento de Farmácia clínica, Porto Alegre, RS, Brazil. tatiaraujocastro@gmail.com
authors.forename: Tatiane Araujo
authors.initials: TA
authors.lastname: Castro
authors.forename: Isabela
authors.initials: I
authors.lastname: Heineck
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000925:Anticoagulants / Q000008:administration & dosage / Q000009:adverse effects / Q000494:pharmacology*; D001938:Brazil; D016303:Clinical Pharmacy Information Systems; D004347:Drug Interactions; D005260:Female; D006785:Hospitals, University; D006801:Humans; D007297:Inpatients; D019934:International Normalized Ratio; D007902:Length of Stay; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D010348:Patient Care Team / Q000458:organization & administration; D010595:Pharmacists / Q000458:organization & administration; D010607:Pharmacy Service, Hospital / Q000458:organization & administration; D011446:Prospective Studies; D014859:Warfarin / Q000008:administration & dosage / Q000009:adverse effects / Q000494:pharmacology*; D055815:Young Adult
chemical_list: D000925:Anticoagulants; D014859:Warfarin