International Journal of Clinical Pharmacy

, Volume 38, Issue 5, pp 1048–1051 | Cite as

Study of warfarin utilization in hospitalized patients: analysis of possible drug interactions

  • Camilo Molino Guidoni
  • Helen Palmira Miranda CamargoEmail author
  • Paulo Roque Obreli-Neto
  • Edmarlon Girotto
  • Leonardo Regis Leira Pereira
Short Research Report


Background Drug–drug interactions in patients taking warfarin may contribute to a higher risk of adverse events. Objective To identify and evaluate the prevalence and characteristics of potential DDIs with warfarin. Methods A cross-sectional study was performed in a Brazilian tertiary hospital. The electronic prescriptions of the patients receiving warfarin between January 2004 and December 2010 were analyzed. Socio-demographic, clinical, and therapeutic variables were collected. Warfarin drug–drug interactions were classified as either risk A, B, C, D, or X according to the Lexi-Interact™ Online database. Results A total of 3048 patients were identified who were prescribed warfarin. Of the 154,161 total drug prescriptions issued, 42,120 (27.3 %) were for warfarin. Evaluation of the prescriptions showed that 63.1 and 0.1 % of patients received concomitant drugs classified as having class D or X risk. It was found that 20,539 (48.7 %) prescriptions had at least one drug with a D or X risk. Patients were prescribed an average of 1.4 (±0.4) concomitant medications with a class D or X warfarin-DDI risk, the most frequent being acetylsalicylic acid and amiodarone. Conclusion The results demonstrate a high prevalence of concomitant drug prescriptions with the potential for clinically relevant DDIs with warfarin, the most frequent being acetylsalicylic acid and amiodarone.


Brazil Drug-drug interaction Pharmacoepidemiology Unified Health System Warfarin 



To the CNPq for a PhD scholarship awarded and the Center for Information and Analysis of the Clinical Hospital of HCFMRP-USP. We thank John Carpenter, Ribeirão Preto, SP, Brazil, for the English revision.


Conflict of interest

The authors declare that they have no conflict of interest.


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Copyright information

© Springer International Publishing 2016

Authors and Affiliations

  • Camilo Molino Guidoni
    • 1
  • Helen Palmira Miranda Camargo
    • 2
    Email author
  • Paulo Roque Obreli-Neto
    • 2
  • Edmarlon Girotto
    • 1
  • Leonardo Regis Leira Pereira
    • 2
  1. 1.State University of LondrinaLondrinaBrazil
  2. 2.Department of Pharmaceutical Sciences, Faculty of Pharmaceutical Sciences of Ribeirão Preto, College of Pharmaceutical Sciences of Ribeirão PretoUniversity of São Paulo (USP)Ribeirao PretoBrazil

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