Skip Navigation LinksHome > September 2000 - Volume 320 - Issue 3 > A Subtherapeutic International Normalized Ratio Despite Incr...
American Journal of the Medical Sciences:
Case Reports

A Subtherapeutic International Normalized Ratio Despite Increasing Doses of Warfarin: Could This Be Malabsorption?

Lara, Luis F. MD; Delgado, Lazaro L. MD; Frazee, Lawrence A. PharmD; HAUPT, KATHY M. MD; RUTECKI, GREGORY W. MD

Collapse Box


Objective: To describe a case of warfarin resistance apparently caused by malabsorption and to review the literature regarding warfarin resistance.

Case Summary: A 28-year-old renal transplant patient with systemic lupus erythematosus was admitted for upper e-tremity thrombophlebitis. Resistance to oral warfarin was demonstrated. Potential causes were investigated. The trapezoidal rule was used to compare the area under the curve for intravenous versus oral dosing of warfarin. The usual bioavailability of warfarin should be 100%. In this patient, warfarin bioavailability after oral dosing was 1.5%. Three potential causes, malabsorption (FF), enzymatic degradation (FG), and first-pass e-traction in the portal circulation (FH), are discussed.

Conclusion: This case demonstrates resistance to warfarin presumably caused by malabsorption.

© Copyright 2000 Southern Society for Clinical Investigation


Article Tools


Search for Similar Articles
You may search for similar articles that contain these same keywords or you may modify the keyword list to augment your search.