Nutrition Warfarin

TABLE 7-9. Potential Warfarin Interactions with Herbal and Nutritional Products... 

Drug/Food interactions Vitamin K-rich vegetables may decrease the anticoagulant effects of warfarin by interfering with absorption. Minimize consumption of vitamin K-rich foods (eg, spinach, seaweed, broccoli, turnip greens) or nutritional supplements. Mango has been shown to increase warfarin s effect. 

The water-soluble salt of vitamin K3 (menadione) should never be used in therapeutics. It is particularly ineffective in the treatment of warfarin overdosage. Vitamin K deficiency frequently occurs in hospitalized patients in intensive care units because of poor diet, parenteral nutrition, recent surgery, multiple antibiotic therapy, and uremia. Severe hepatic failure results in diminished protein synthesis and a hemorrhagic diathesis that is unresponsive to vitamin K. 

An interaction of warfarin with a nutritional supplement containing vitamin K has been reported (41). 

This report underlines the need for monitoring the use of nutritional and herbal products in patients taking warfarin. 

Bransgrove LL. Interaction between warfarin and a vitamin K-containing nutritional supplement a case report. J Herbal Pharmacother 2001 1 85-9. 

Soybean oil is widely used intramuscularly as a drug vehicle or as a component of emulsions used in parenteral nutrition regimens it is also consumed as an edible oil. Generally, soybean oil is regarded as an essentially nontoxic and nonirritant material. However, serious adverse reactions to soybean oil emulsions administered parenterally have been reported. These include cases of hypersensitivity, CNS reactions, " and fat embolism. " Interference with the anticoagulant effect of warfarin has also been reported. ... 

Although the average weekly dose of warfarin is between 30 and 40 mg, some patient-related variables are associated with a lower than usual dose advanced age (>65 years), elevated baseline INR, poor nutritional status, liver disease, hyperthyroidism, and concurrent use of medications known to enhance the effect of warfarin (Table 19-12). Prior to initiating therapy, the clinician should screen for the presence of contraindications to anticoagulation therapy and risk factors for... 

None of these interactions is very well documented, and their clinical relevance is unclear. Note that vitamin K in food commonly interacts with warfarin, and these interactions are discussed in Coumarins and related drugs + Foods Vitamin Kj-rich , p.409. See also cranberry juice , (p.398), enteral and parenteral nutrition , (below), grapefruit juice , (p.411), mango , (p.408) and soya bean products , (p.408). 

A number of early case reports described warfarin resistance in patients taking enteral feeds that contained high levels of added vitamin Kx- These products were then reformulated to contain lower amounts of vitamin Kx, commonly now about 4 to 10 micrograms per 100 mL however, some cases of interactions have still been reported, and one study in children reported that those receiving enteral nutrition (mostly vitamin K enriched formula) required 2.4-fold higher maintenance warfarin doses. Lipid emulsions containing soya oil might contain sufBcient natural vitamin Kx to alter warfarin requirements. Parenteral multivitamin preparations may also contain vitamin Kx. 

In a prospective cohort study in 319 children, the use of enteral nutrition (mostly vitamin K supplemented formula, and some vitamin K supplemented tube feeds) was associated with a higher dose of warfarin to achieve a target INR (0.28 versus 0.16 mg/kg) and similarly a higher dose of warfarin was needed to maintain the INR (0.26 versus 0.11 mg/kg). ... 

Fat emulsions used for parenteral use containing soya oil may themselves contain sufficient vitamin Kj for daily needs. Parenteral multivitamin preparations may also contain important levels of vitamin Kj. It would be advisable to keep the vitamin Kj intake constant in any patient requiring long-term supplemental or total parenteral nutrition and warfarin. If the amount of lipid and/or multivitamins is altered, antieipate a... 

Parr MD, Record KE, Griffith GL, Zeok JV, Todd EP. Effect of enteral nutrition on warfarin therapy. ClinPharm (1982) 1, 274-6. 

Howard PA, Hannaman KN. Warfarin resistance linked to enteral nutrition products. J Am Diet Assoc ( 9S5) 85, 713-15. 

Soya oil is an important source of dietary vitamin K, see Table 12.3 , (p.407). For two cases of warfarin resistance with intravenous soya oil emulsions, see Coumarins and related drugs + Foods Enteral and parenteral nutrition , p.406. 

A 72-year-old man stabilised on warfarin was found to have an INR of 4.43 at a routine clinic visit, which was increased from 3.07 six weeks previously. The patient had stopped taking a herbal product Nature s Life Greens that month because he did not have enough money to buy it. He had been taking it for the past 7 years as a vitamin supplement because he had previously been instructed to limit his intake of green leafy vegetables. He was eventually restabilised on warfarin and the same nutritional product. 

This case reinforces the view that all patients taking warfarin should seek advice when they want to stop or start any herbal medicine or nutritional supplement. 

Nutrition The effect of warfarin therapy for 6 months on folate status has been studied in 114 patients, using measurements of erythrocyte folate and 5-methyltetrahydro-folate and plasma folate, total homocysteine, phylloquinone, vitamin B12, and methylmalonic acid [ll. There were significant falls in total erythrocyte folate and 5-methyltetrahydrofolate and a concurrent increase in plasma phylloquinone, attributed to altered vitamin K metabolism. 

Dickerson RN. Warfarin resistance and enteral tube feeding a vitamin K-indepen-dent interaction. Nutrition 2008 24(10) 1048-52. 

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