Vitamin K-independent warfarin resistance after concurrent administration of warfarin and continuous enteral nutrition.
OBJECTIVE
To assess the influence of withholding continuous enteral nutrition for 1 hour before and after warfarin administration compared with the coadministration of warfarin with continuous enteral nutrition on changes in international normalized ratios (INRs).


METHODS
Retrospective, crossover case series.


METHODS
Intensive care units of a university-affiliated medical center.


METHODS
Six adults who required nutritional support for at least the first 10 consecutive days of warfarin therapy; during that 10-day period, they had a period of at least 3 consecutive days during which the enteral feeding was withheld for 1 hour before and after warfarin administration, and had a period of at least 3 consecutive days when feedings were not withheld during warfarin administration. Patients with advanced liver disease and those who received therapies, during the observation period, that significantly alter warfarin metabolism were omitted from the study.


RESULTS
The change in INR during the 3-day observation period when feedings were withheld for 1 hour before and after warfarin administration was significantly different versus the change in INR during coadministration of warfarin with continuous feeding (mean +/- SD 0.74 +/- 0.66 vs -0.13 +/- 0.81, p < or = 0.05). This difference in INR response occurred despite the administration of similar dosages of warfarin (5.6 +/- 2.1 vs 5.7 +/- 2.1 mg/day, p>0.05). Also noted was a clinically irrelevant, but statistically significant, difference in vitamin K intake between treatment periods (77 +/- 36 mug/day when feedings were withheld vs 102 +/- 28 microg/day when feedings were not withheld, p < or = 0.05).


CONCLUSIONS
Continuous enteral nutrition should be withheld for 1 hour before and after warfarin administration to prevent enteral nutrition-associated warfarin resistance.
Dickerson
Roland N
RN
Department of Clinical Pharmacy, University of Tennessee Center for the Health Sciences, Memphis, Tennessee 38163, USA. rdickerson@utmem.edu
Garmon
Wesley M
WM
Kuhl
David A
DA
Minard
Gayle
G
Brown
Rex O
RO
D000925:Anticoagulants / Q000008:administration & dosage / Q000627:therapeutic use*; D000933:Antifibrinolytic Agents / Q000008:administration & dosage*; D004334:Drug Administration Schedule; D004351:Drug Resistance; D004750:Enteral Nutrition; D005260:Female; D018565:Food-Drug Interactions; D006801:Humans; D019934:International Normalized Ratio; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D014812:Vitamin K / Q000008:administration & dosage*; D014859:Warfarin / Q000008:administration & dosage / Q000627:therapeutic use*
D000925:Anticoagulants; D000933:Antifibrinolytic Agents; D014812:Vitamin K; D014859:Warfarin