Practice parameter update: management issues for women with epilepsy--focus on pregnancy (an evidence-based review): vitamin K, folic acid, blood levels, and breastfeeding: report of the Quality Standards Subcommittee and Therapeutics and Technology Assessment Subcommittee of the American Academy of Neurology and American Epilepsy Society

OBJECTIVE

To reassess the evidence for management issues related to the care of women with epilepsy (WWE) during pregnancy, including preconceptional folic acid use, prenatal vitamin K use, risk of hemorrhagic disease of the newborn, clinical implications of placental and breast milk transfer of antiepileptic drugs (AEDs), risks of breastfeeding, and change in AED levels during pregnancy.

METHODS

A 20-member committee evaluated the available evidence based on a structured literature review and classification of relevant articles published between 1985 and October 2007.

RESULTS

Preconceptional folic acid supplementation is possibly effective in preventing major congenital malformations in the newborns of WWE taking AEDs. There is inadequate evidence to determine if the newborns of WWE taking AEDs have a substantially increased risk of hemorrhagic complications. Primidone and levetiracetam probably transfer into breast milk in amounts that may be clinically important. Valproate, phenobarbital, phenytoin, and carbamazepine probably are not transferred into breast milk in clinically important amounts. Pregnancy probably causes an increase in the clearance and a decrease in the concentration of lamotrigine, phenytoin, and to a lesser extent carbamazepine, and possibly decreases the level of levetiracetam and the active oxcarbazepine metabolite, the monohydroxy derivative.

RECOMMENDATIONS

Supplementing women with epilepsy with at least 0.4 mg of folic acid before they become pregnant may be considered (Level C). Monitoring of lamotrigine, carbamazepine, and phenytoin levels during pregnancy should be considered (Level B) and monitoring of levetiracetam and oxcarbazepine (as monohydroxy derivative) levels may be considered (Level C). A paucity of evidence limited the strength of many recommendations.

Vitamin K supplementation and progression of coronary artery calcium in older men and women

BACKGROUND

Coronary artery calcification (CAC) is an independent predictor of cardiovascular disease. A preventive role for vitamin K in CAC progression has been proposed on the basis of the properties of matrix Gla protein (MGP) as a vitamin K-dependent calcification inhibitor.

OBJECTIVE

The objective was to determine the effect of phylloquinone (vitamin K1) supplementation on CAC progression in older men and women.

DESIGN

CAC was measured at baseline and after 3 y of follow-up in 388 healthy men and postmenopausal women; 200 received a multivitamin with 500 microg phylloquinone/d (treatment), and 188 received a multivitamin alone (control).

RESULTS

In an intention-to-treat analysis, there was no difference in CAC progression between the phylloquinone group and the control group; the mean (+/-SEM) changes in Agatston scores were 27 +/- 6 and 37 +/- 7, respectively. In a subgroup analysis of participants who were > or =85% adherent to supplementation (n = 367), there was less CAC progression in the phylloquinone group than in the control group (P = 0.03). Of those with preexisting CAC (Agatston score > 10), those who received phylloquinone supplements had 6% less progression than did those who received the multivitamin alone (P = 0.04). Phylloquinone-associated decreases in CAC progression were independent of changes in serum MGP. MGP carboxylation status was not determined.

CONCLUSIONS

Phylloquinone supplementation slows the progression of CAC in healthy older adults with preexisting CAC, independent of its effect on total MGP concentrations. Because our data are hypothesis-generating, further studies are warranted to clarify this mechanism. This trial was registered at clinicaltrials.gov as NCT00183001.

On the influence of vitamin K-rich vegetables and wine on the effectiveness of warfarin treatment

Thrombotest (TT) values were studied in patients fed an ordinary diet and on continuous and well controlled warfarin therapy because of deep venous thrombosis or pulmonary embolism. The aim was to characterize the effect of single and multiple administrations (daily during one week) of vitamin K1 (Konakion), vitamin K-rich vegetables such as spinach and broccoli, and table wine. Single administration of 250 micrograms vitamin K1, 250 g spinach, 250 g broccoli and 37.5 cl wine did not result in TT-values outside the therapeutic range. However, when Konakion, broccoli and spinach were given daily during one week the TT-values tended to rise above the therapeutic limit, requiring dose adjustment. On the basis of this study it appears that excessive intake of vitamin K-rich food and a moderate intake of alcohol on one occasion may be permitted during anticoagulant therapy.

Vitamin A and retinol intakes and the risk of fractures among participants of the Women's Health Initiative Observational Study

BACKGROUND

Excessive intakes of vitamin A have been shown to have adverse skeletal effects in animals. High vitamin A intake may lead to an increased risk of fracture in humans.

OBJECTIVE

The objective was to evaluate the relation between total vitamin A and retinol intakes and the risk of incident total and hip fracture in postmenopausal women.

DESIGN

A total of 75,747 women from the Women's Health Initiative Observational Study participated. The risk of hip and total fractures was determined using Cox proportional hazards models according to different intakes of vitamin A and retinol.

RESULTS

In the analysis adjusted for some covariates (age; protein, vitamin D, vitamin K, calcium, caffeine, and alcohol intakes; body mass index; hormone therapy use; smoking; metabolic equivalents hours per week; ethnicity; and region of clinical center), the association between vitamin A intake and the risk of fracture was not statistically significant. Analyses for retinol showed similar trends. When the interaction term was analyzed as categorical, the highest intake of retinol with vitamin D was significant (P = 0.033). Women with lower vitamin D intake (< or =11 microg/d) in the highest quintile of intake of both vitamin A (hazard ratio: 1.19; 95% CI: 1.04, 1.37; P for trend: 0.022) and retinol (hazard ratio: 1.15; 95% CI: 1.03, 1.29; P for trend: 0.056) had a modest increased risk of total fracture.

CONCLUSIONS

No association between vitamin A or retinol intake and the risk of hip or total fractures was observed in postmenopausal women. Only a modest increase in total fracture risk with high vitamin A and retinol intakes was observed in the low vitamin D-intake group.

Vitamin K supplementation in postmenopausal women with osteopenia (ECKO trial): a randomized controlled trial

BACKGROUND

Vitamin K has been widely promoted as a supplement for decreasing bone loss in postmenopausal women, but the long-term benefits and potential harms are unknown. This study was conducted to determine whether daily high-dose vitamin K1 supplementation safely reduces bone loss, bone turnover, and fractures.

METHODS AND FINDINGS

This single-center study was designed as a 2-y randomized, placebo-controlled, double-blind trial, extended for earlier participants for up to an additional 2 y because of interest in long-term safety and fractures. A total of 440 postmenopausal women with osteopenia were randomized to either 5 mg of vitamin K1 or placebo daily. Primary outcomes were changes in BMD at the lumbar spine and total hip at 2 y. Secondary outcomes included changes in BMD at other sites and other time points, bone turnover markers, height, fractures, adverse effects, and health-related quality of life. This study has a power of 90% to detect 3% differences in BMD between the two groups. The women in this study were vitamin D replete, with a mean serum 25-hydroxyvitamin D level of 77 nmol/l at baseline. Over 2 y, BMD decreased by -1.28% and -1.22% (p = 0.84) (difference of -0.06%; 95% confidence interval [CI] -0.67% to 0.54%) at the lumbar spine and -0.69% and -0.88% (p = 0.51) (difference of 0.19%; 95% CI -0.37% to 0.75%) at the total hip in the vitamin K and placebo groups, respectively. There were no significant differences in changes in BMD at any site between the two groups over the 2- to 4-y period. Daily vitamin K1 supplementation increased serum vitamin K1 levels by 10-fold, and decreased the percentage of undercarboxylated osteocalcin and total osteocalcin levels (bone formation marker). However, C-telopeptide levels (bone resorption marker) were not significantly different between the two groups. Fewer women in the vitamin K group had clinical fractures (nine versus 20, p = 0.04) and fewer had cancers (three versus 12, p = 0.02). Vitamin K supplements were well-tolerated over the 4-y period. There were no significant differences in adverse effects or health-related quality of life between the two groups. The study was not powered to examine fractures or cancers, and their numbers were small.

CONCLUSIONS

Daily 5 mg of vitamin K1 supplementation for 2 to 4 y does not protect against age-related decline in BMD, but may protect against fractures and cancers in postmenopausal women with osteopenia. More studies are needed to further examine the effect of vitamin K on fractures and cancers.

TRIAL REGISTRATION

ClinicalTrials.gov (#NCT00150969) and Current Controlled Trials (#ISRCTN61708241).

[Evidence of dietary therapy for osteoporosis]

A significant point of dietary therapy for osteoporosis is that calcium, vitamin D and vitamin K are recommended to be actively administered on top of sufficient intake of energy and the other nutrients including protein. In Japanese guidelines for the prevention and treatment of osteoporosis 2006 edition, daily intake of calcium and vitamin D is encouraged at least 800mg and 400 to 800IU (10 to 20microg) , respectively. Calcium and vitamin D are also important for maximizing the effect of drug for osteoporosis. Calcium and vitamin D supplementation could be a supportive measure, when their necessary requirement is difficult to be consumed.

[Patient with warfarin poisoning caused by coumarin rodenticide]

We report a patient who attempted suicide by taking warfarin as a coumarin rodenticide twice, and showed oral bleeding and an abnormally prolonged bleeding tendency after 10 days. He was conscious. His body temperature was 36.6 degrees C, the respiratory rate was 23/min, and blood pressure was 142/87 mmHg. A bite wound showing continuous bleeding was observed on the right side of the oral cavity. CT of the head and upper gastrointestinal endoscopy showed no intracranial and gastrointestinal bleeding,respectively. The PT and INR were extremely high, and complete blood count revealed anemia. Blood chemistry showed hypoproteinemia. Occult blood was strongly positive. Routine urine examination and electrocardiography showed neither abnormal nor characteristic findings. In drug/ poison screening tests, GC/MS analysis revealed warfarin artifacts in serum and urine samples. Warfarin was isolated from each sample, converted to a TMS derivative, and quantified by SIM analysis of GC/MS. During the clinical course, KaytwoN (vitamin K) was intravenously administered at a dose of 20 mg since the INR at the first consultation was 20.89. After admission to the ICU, 20 mg Kaywan (vitamin K) was orally administered, and the INR after 5 hours improved to 2.32. Kaywan administration (20 mg/day) was initiated, and he improved and was discharged 5 days after admission. The definite cause could be clarified by drug/poison analysis, and effective treatment could be performed.

Enhancement of skin penetration of vitamin K using monoolein-based liquid crystalline systems

Application of vitamin K (vitK) to the skin has been used for suppression of pigmentation and resolution of bruising. However, there is no report concerning the extent of its penetration in the skin. In this study, we investigated the in vitro skin penetration and transdermal delivery of vitK, and whether these parameters may be enhanced by lipid-based drug delivery systems. The lipid formulation used in this study contains monoolein (MO), which is structured as a liquid crystalline phase, named hexagonal phase. The skin penetration of vitK was assessed in vitro using porcine ear skin mounted in a Franz diffusion cell. VitK (2.5%, w/w) was incorporated in either of three formulations: liquid vaseline, MO-based hexagonal phase gel (MO-vitK-water at 77.5/2.5/20, w/w/w) and MO-based nanodispersion of hexagonal phase (MO-vitK-poloxamer-water at 15/2.5/0.9/81.6, w/w/w/w). When vaseline was used, vitK was delivered mainly to the stratum corneum (SC): 9.50+/-0.97 microg/cm(2) of vitK was delivered to the SC at 12 h post-application, whereas 4.90 +/- 1.28 microg/cm(2) of vitK was delivered to the epidermis (E)+dermis (D) at the same time point. The hexagonal phase gel and the nanodispersion delivered approximately 2 times more vitK to the SC and 2.0-3.7 times more vitK to the [E+D] than the vaseline solution. The nanodispersion (but not the gel) also increased the transdermal delivery of vitK at 9 h ( approximately 3-fold increase). These results demonstrate that the topical delivery of vitK incorporated in a lipophilic vehicle is small, but it may be enhanced by MO-based systems, which might be useful to increase the effectiveness of topical vitK therapy.

[Renal osteodystrophy and vitamin K. Vitamin K and dialysis]

Those who have already suffered from bone fractures have been found to have lower serum vitamin K (VK) concentrations than age-matched controls. Also in dialysis patients, serum VK(1) concentration are reported to be significantly lower in patients with previous fractures compared to those without. In most studies, there are no significant changes in the serum Ca, P, and intact PTH levels during the VK administration in dialysis patients. Investigation of the changes in metabolic bone markers, such as bone specific alkaline phosphatase (BAP) , during the VK therapy has yielded various results. Although the reason for these discrepancy is not well understood, it may be attributed to the differences in clinical features, including parathyroid function of the patients and to the differences in VK administered.

Daily vitamin K supplementation improves anticoagulant stability

BACKGROUND

One of the causes of unstable anticoagulant control in patients using vitamin K antagonists is a fluctuating intake of vitamin K. Research suggests that patients with a low dietary intake of vitamin K have a less stable anticoagulant control than patients with a higher intake.

OBJECTIVES

To study whether supplementation with a low daily dose of vitamin K improves anticoagulant control.

METHODS

We performed a double-blind, randomized, placebo-controlled trial. 200 patients of the Leiden anticoagulation clinic, who used the vitamin K antagonist phenprocoumon, were randomized to receive either adjusted-dose phenprocoumon and 100 mug vitamin K once daily or adjusted-dose phenprocoumon and a placebo. Treatment duration was 24 weeks. The primary outcome was the percentage of time the International Normalized Ratio was within the therapeutic range.

RESULTS

The time in the therapeutic range was 85.5% in the placebo group and 89.5% in the vitamin K group (adjusted difference 3.6%; 95% CI -0.8% to 8.0%). The time below the therapeutic range was 3.1% in the placebo group and 2.1% in the vitamin K group (adjusted difference -0.7%; 95% CI -2.5% to 1.1%) and the time above the therapeutic range was 11.4% in the placebo group and 8.5% in the vitamin K group (adjusted difference -2.9%; 95% CI -6.9% to 1.1%). The relative risk (RR) of a maximal stability in the vitamin K group compared to the placebo group was 1.8 (95%, CI 1.1-2.7).

CONCLUSION

Supplementation of vitamin K antagonists with 100 mug vitamin K improves stability of anticoagulant therapy. Because the risk of side effects is inversely related to anticoagulant stability, such an improvement is likely to reduce the number of bleeding and thrombotic events.

Effectiveness of Factor IX Complex Concentrate in Reversing Warfarin Associated Coagulopathy for Intracerebral Hemorrhage

INTRODUCTION

The objective of this study is to show the effectiveness of Factor IX complex concentrate (FIXCC) for rapid reversal of an elevated International Normalized Ratio (INR) in patients with anticoagulation-associated intracerebral hemorrhage (AAICH).

METHODS

We, retrospectively, analyzed the clinical data of 19 patients with the diagnosis of AAICH from January 2005 to May 2006. A comparison was made among patients treated with FFP and Vit.K [FFP-group (n = 9)] and patients treated with FIXCC in addition to FFP and Vit.K [FIXCC-group (n = 10)]. INR of 1.4 or less was taken as target.

RESULTS

Mean INR on admission for FFP and FIXCC group was 1.84 +/- 0.31 and 2.44 +/- 1.48, respectively (P = 0.315). After administration of therapy, the INR was reduced from 1.84 +/- 0.31 to 1.34 +/- 0.08 (P < 0.05) in FFP group and 2.44 +/- 1.48 to 1.34 +/- 0.07 (P < 0.005) in FIXCC group. Three patients in FFP group (33%) and 8 patients in FIXCC group (80%) reached their target INR in 3-4 h after initiation of therapy (P = 0.012). Mean time taken by both FFP and FIXCC groups to reach the target INR was 8.52 +/- 5.60 h and 4.25 +/- 2.12 h, respectively (P < 0.05). The mean rate of INR correction was 0.06 +/- 0.03 and 0.27 +/- 0.25 per hour for the FFP and FIXCC group, respectively (P < 0.005). There was one death in FIX group and two in FFP group and no thrombotic complications.

CONCLUSION

Our data suggests that FIXCC in combination with FFP and Vit.K may result in decreased time required when compared to FFP and Vit.K alone for correction of warfarin associated coagulopathy in neurosurgical emergencies.

Vitamin K deficiency bleeding: the readiness is all

Perspective on the papers by Busfield et al and McNinch et al (see pages 754 and 759 )

Current pharmacogenetic developments in oral anticoagulation therapy: the influence of variant VKORC1 and CYP2C9 alleles

For decades coumarins have been the most commonly prescribed drugs for therapy and prophylaxis of thromboembolic conditions. Despite the limitation of their narrow therapeutic dosage window, the broad variation of intra- and inter-individual drug requirement, and the relatively high incidence of bleeding complications, prescriptions for coumarins are increasing due to the aging populations in industrialised countries. The identification of the molecular target of coumarins, VKORC1, has greatly improved the understanding of coumarin treatment and illuminated new perspectives for a safer and more individualized oral anticoagulation therapy. Mutations and SNPs within the translated and non-translated regions of the VKORC1 gene have been shown to cause coumarin resistance and sensitivity, respectively. Besides the known CYP2C9 variants that affect coumarin metabolism, the haplotype VKORC1*2 representing a frequent SNP within the VKORC1 promoter has been identified as a major determinant of coumarin sensitivity, reducing VKORC1 enzyme activity to 50% of wild type. Homozygous carriers of the VKORC1*2 allele are strongly predisposed to coumarin sensitivity. Using individualized dose adaptation, a significant reduction of bleeding complications can be expected, especially in the initial drug saturation phase. Furthermore, concomitant application of low dose vitamin K may significantly reduce intra-individual coumarin dose variation and, thus, may stabilize oral anticoagulation therapy. The use of new pharmacogenetics-based dosing schemes and the concomitant application of low-dose vitamin K with coumarins will decidedly influence the current practice of oral anticoagulation and greatly improve coumarin drug safety.

Neonatal vitamin K prophylaxis in Great Britain and Ireland: the impact of perceived risk and product licensing on effectiveness

OBJECTIVE

To determine current use of vitamin K (VK) prophylaxis in newborns and review the efficacy and effectiveness of regimens used.

DESIGN

Efficacy and effectiveness calculated using current practice details, data from Southern Ireland and two previous surveys, together with contemporaneous studies of vitamin K deficiency bleeding (VKDB).

SETTING

Current survey: United Kingdom (Great Britain and Northern Ireland). Efficacy and effectiveness tables: United Kingdom and Southern Ireland.

MAIN OUTCOME MEASURES

Current VK prophylaxis following uncomplicated term deliveries. Relative risk of VKDB calculated for the VK actually received and for "intention to treat".

RESULTS

Questionnaire response rate 95% (n = 243), all recommending VK prophylaxis. No association between unit size and route of administration. For uncomplicated term deliveries, 60% recommended intramuscular (IM) prophylaxis, 24% oral and 16% offered both routes without bias. All units offering IM gave a single dose, mostly 1 mg Konakion Neonatal. Oral regimens showed more variation: two thirds gave 2 mg (range 0.5-2 mg), the number of doses ranged from 1 to 11 and many used preparations off-licence or the unlicensed Orakay. IM prophylaxis, if given, provided the best protection (most efficacious) against VKDB. However, on an intention-to-treat basis (effectiveness), there is no statistically significant difference between the risks of VKDB after intended IM VK and after oral prophylaxis intended to continue beyond a week.

CONCLUSIONS

Although the principles of VK prophylaxis is now accepted by all, there is no uniformity in practice. Omission of prophylaxis appears to be a greater problem for IM than for multi-dose oral prophylaxis, affecting overall effectiveness.

Warfarin cessation before cardiopulmonary bypass: lessons learned from a randomized controlled trial of oral vitamin K

BACKGROUND

No standard protocol of warfarin cessation and bridging for cardiac surgery exists. This study examined a single institution's protocol with respect to timing of cessation and low molecular weight heparin bridging. The recovery of vitamin K-dependent factors and the effects of cardiopulmonary bypass on coagulation factors were explored. Administration of preoperative oral vitamin K was investigated in a randomized, placebo-controlled trial. A post hoc analysis examined residual anti-Xa activity of enoxaparin bridging.

METHODS

Forty patients on warfarin undergoing cardiopulmonary bypass were randomized to receive 5 mg of oral vitamin K or placebo 6 days before surgery. Blood samples were acquired at six times and assayed for prothrombin time, anti-Xa activity, and functional levels of factors II, V, VII, and IX and of protein C. Measures of bleeding and transfusion were also collected.

RESULTS

No difference in bleeding or transfusion was observed between the treatment groups. Appropriate recovery of coagulation factors was observed with warfarin cessation irrespective of treatment group. The coagulation factors decreased by an average of 0.36 units/mL during the period of surgery. Enoxaparin 1 mg/kg until the evening before surgery resulted in 70% of patients entering the operating room with therapeutic anti-Xa activity (0.6 +/- 0.3 units/mL).

CONCLUSIONS

The cessation of warfarin 6 days preoperatively is sufficient for functional recovery of vitamin K-dependent factors, which undergo significant changes during the operative course. A 5-mg dose of vitamin K with warfarin discontinuation did not enhance recovery of vitamin K-dependent factors and is unnecessary. With the observation that enoxaparin up until the night before surgery resulted in high residual anti-Xa levels in the operating room, our center now administers the last dose of enoxaparin 24 hours before surgery.

Serum percentage undercarboxylated osteocalcin, a sensitive measure of vitamin K status, and its relationship to bone health indices in Danish girls

Recent cross-sectional data suggest that better vitamin K status in young girls (aged 3-16 years) is associated with decreased bone turnover, even though it is not associated with bone mineral content (BMC). The objective of the present study was to investigate the relationship between serum percentage of undercarboxylated osteocalcin (%ucOC), as an index of vitamin K status, and BMC and biochemical indices of bone turnover in peri-pubertal Danish girls. This peri-pubertal stage is a dynamic period of bone development, and as such, may represent an important window of opportunity for vitamin K status to modulate childhood bone health. Serum %ucOC and serum 25-hydroxyvitamin D (25 (OH) D) were measured at baseline in a study of 223 healthy girls aged 11-12 years. Urinary pyridinium crosslinks of collagen and serum total osteocalcin as markers of bone resorption and formation, respectively, as well as BMC (total body and lumbar spine) were also measured. Serum %ucOC (median 21.9 %) was not associated with markers of bone resorption or with total osteocalcin. Serum %ucOC was inversely correlated with serum 25 (OH) D (r - 0.143; P < 0.05). Serum %ucOC was negatively associated with BMC of the total body (beta - 0.045; P < 0.001) and lumbar spine (beta - 0.055; P < 0.05), after adjustment for potential confounders including vitamin D status. Better vitamin K status was associated with increased BMC, but not bone turnover, in healthy peri-pubertal Danish girls. There is a need for well-designed, randomized phylloquinone supplementation trials in children and adolescents to confirm epidemiological findings of an association between vitamin K status and bone health.

Regression of warfarin-induced medial elastocalcinosis by high intake of vitamin K in rats

Arterial calcification (AC) is generally regarded as an independent risk factor for cardiovascular morbidity and mortality. Matrix Gla protein (MGP) is a potent inhibitor of AC, and its activity depends on vitamin K (VK). In rats, inactivation of MGP by treatment with the vitamin K antagonist warfarin leads to rapid calcification of the arteries. Here, we investigated whether preformed AC can be regressed by a VK-rich diet. Rats received a calcification-inducing diet containing both VK and warfarin (W&K). During a second 6-week period, animals were randomly assigned to receive either W&K (3.0 mg/g and 1.5 mg/g, subsequently), a diet containing a normal (5 microg/g) or high (100 microg/g) amount of VK (either K1 or K2). Increased aortic calcium concentration was observed in the group that continued to receive W&K and also in the group changed to the normal dose of VK and AC progressed. Both the VK-rich diets decreased the arterial calcium content by some 50%. In addition, arterial distensibility was restored by the VK-rich diet. Using MGP antibodies, local VK deficiency was demonstrated at sites of calcification. This is the first study in rats demonstrating that AC and the resulting decreased arterial distensibility are reversible by high-VK intake.

Picking a bone with contemporary osteoporosis management: Nutrient strategies to enhance skeletal integrity

Epidemic rates of osteoporosis in the western world have yielded intense efforts to develop management approaches to combat this potentially devastating disorder; recent research has unveiled innovative strategies which hold considerable promise for prevention of skeletal compromise and amelioration of suboptimal bone health. According to many algorithms and practice directives, the contemporary assessment and management of osteoporosis focuses heavily on determination of fracture risk and pharmaceutical intervention for those patients deemed to be at high risk. While routine recommendations for calcium and vitamin D have been incorporated into most regimens, disproportionately little attention has been given to recent research elucidating improved bone health and diminution in fracture rates experienced by patients receiving specific nutrients. In mainstream medical practice, clinical analysis and management of nutritional or dietary issues is sometimes perceived as unconventional, primitive or unsophisticated health care. Recent evidence-based research, however, supports intervention with adequate amounts of specific nutrients including vitamin D, strontium, vitamin K, and essential fatty acids in the prevention and primary management of osteoporosis.

Low-dose oral vitamin K to normalize the international normalized ratio prior to surgery in patients who require temporary interruption of warfarin

BACKGROUND

In patients who require warfarin interruption before surgery and have an elevated international normalized ratio (INR) before surgery, low-dose vitamin K may normalize the INR in time for surgery.

PATIENTS AND METHODS

In a retrospective cohort study, we assessed the efficacy of 1 mg oral vitamin K to normalize the INR for surgery and whether resistance to re-anticoagulation occurs when warfarin is restarted after surgery. We studied a cohort of patients with an INR 1.4-1.9 on the day before surgery who received 1 mg oral vitamin K (vitamin K group), and a comparator group of patients with a normal INR (< or = 1.3) on the day before surgery who did not receive vitamin K (no vitamin K group). In both patient groups, we determined the proportion of patients with a normalized INR on the day of surgery and compared the mean INR after surgery when warfarin was resumed.

RESULTS

Of 43 patients in the vitamin K group, the INR was normalized (< or = 1.3) in 33 patients (76.6; 95% confidence interval [CI]: 64.1-89.4), and the INR was normal or near-normal (< or = 1.4) in 39 patients (90.7; 95% CI: 82.0-99.4) on the day of surgery. The mean (standard deviation) INR in the vitamin K and no vitamin K group 4-8 days after surgery was 1.75 (0.34) and 1.59 (0.36), respectively (P = 0.56).

CONCLUSIONS

In patients requiring interruption of warfarin for surgery, 1 mg oral vitamin K on the day before surgery can normalize the INR by the day of surgery and may not confer resistance to warfarin re-anticoagulation after surgery.

Pronounced elevation of undercarboxylated osteocalcin in healthy children

The vitamin K-dependent protein osteocalcin is thought to play an important role in bone metabolism. Osteocalcin contains glutamic acid (Gla) residues, which have a high affinity for calcium. Vitamin K acts as an indispensable cofactor for the formation of these residues. Inadequate dietary vitamin K intake results in the synthesis of undercarboxylated (i.e. inactive) osteocalcin (ucOC). In adults, low vitamin K status of bone is associated with low bone density and increased risk of osteoporotic fractures. Little is known about vitamin K status and bone health in children. We used a cross-sectional study design to compare the vitamin K status of bone in healthy children (n = 86) with that of adults (n = 30). In children, a marked elevation of the ratio of ucOC/carboxylated osteocalcin (cOC), indicative of a poor vitamin K status, was observed. This difference persisted after adjusting for age, gender, puberty, height, weight. Furthermore, a marked correlation between the bone markers for bone metabolism and ucOC and cOC was found in the children's group. These findings suggest a pronounced low vitamin K status of bone during growth. The question remains, however, whether children would benefit from higher vitamin K intake, for instance, by improved bone health or stronger bones.

Prospective study of supplemental vitamin K therapy in patients on oral anticoagulants with unstable international normalized ratios

BACKGROUND

It is not known whether patients on oral vitamin K antagonists who have unstable INRs achieve more stable INRs with daily vitamin K supplementation. We sought to determine whether vitamin K supplementation may decrease INR variability in patients with a history of unstable INRs, how soon the INR decreases after vitamin K therapy is initiated, the time to reach a therapeutic INR after vitamin K initiation, and how much of an increase in oral anticoagulant dose is needed to maintain the INR in the desired range.

METHODS

This is a prospective open label crossover study of patients on warfarin with a history of fluctuating INRs. A 9 week observation phase was followed by an 8 week period with patients receiving 500 microg of oral vitamin K daily. INRs were determined once weekly with a home point of care monitoring instrument.

RESULTS

Vitamin K supplementation led to a decrease in INR variability in five of the nine patients studied (56%). INR decrease occurred 2-7 days after initiation of vitamin K. Therapeutic INRs were achieved 2-35 days after vitamin K therapy was initiated and an increase in warfarin dose of 6-95% was required to bring the INR back into the therapeutic range.

CONCLUSIONS

INR fluctuations may decrease in selected patients with unstable INRs who receive vitamin K supplementation. A study with a larger sample size and longer follow-up period is needed. The results of the present study can help design such a study.

The future prospects of pharmacogenetics in oral anticoagulation therapy

Coumarins are the mainstay of oral anticoagulation for the treatment and prophylaxis of thromboembolic disorders. They have a narrow therapeutic index and regular monitoring is therefore required to avoid serious adverse effects. There is wide interindividual variability in dosage requirements, which makes anticoagulation response unpredictable. Current dosing titrations are haphazard and inconvenient and poor initial control leads to morbidity, and occasional mortality, because of bleeding and further thromboembolism. Recent discoveries have helped to characterize the factors that contribute to the interindividual variability in responses to coumarins. Patient and environmental factors that affect anticoagulation response to coumarins include age, body size, dietary vitamin K status, concurrent disease and drug interactions. More recently, single nucleotide polymorphisms in the 2C9 isoform of cytochrome P450 (CYP2C9) and vitamin K epoxide reductase (VKOR) have been shown to make significant contributions to the variability in coumarin dosage requirements. Polymorphisms in other genes that mediate the actions of coumarins may also contribute to this variability. Racial and cultural differences influence dosage requirements, which can be explained, at least in part, by genetic and dietary factors. Incorporation of genetic and environmental factors could help in the prediction of more individualized loading and maintenance doses for safer anticoagulation therapy.

Vitamin K status in the elderly

PURPOSE OF REVIEW

Poor vitamin K nutrition has recently been linked to several chronic diseases associated with abnormal calcification, which affect many elderly. To understand the impact of vitamin K nutrition on healthy aging it is necessary to assess both the determinants and the adequacy of vitamin K nutritional status of the elderly.

RECENT FINDINGS

Overall, elderly persons consume more vitamin K than young adults. However, a subgroup of the elderly population does not meet the current recommended dietary intakes for this nutrient. The first meta-analysis evaluating the data on the role of vitamin K and bone health concluded that increased intakes of vitamin K are warranted to reduce bone loss and fracture risk among the elderly. Recent studies suggest that nondietary determinants of vitamin K status need to be factored into any discussion on the adequacy of nutritional status of the elderly. One promising area of research is the interrelationship between estrogen and vitamin K.

SUMMARY

Evidence is emerging to support recommendations to increase intakes of vitamin K among the elderly to reduce bone loss and fracture risk. Much more research is required, however, to identify nondietary determinants of vitamin K status, and their impact on the elderly.

Polymorphisms of the Factor VII Gene Associated with the Low Activities of Vitamin K-Dependent Coagulation Factors in One-Month-Old Infants

Despite administration of vitamin K (VK), some infants show lower activity of VK-dependent coagulation factors and they could develop intracranial hemorrhage. For preventing VK deficiency bleeding (VKDB) in infants, oral administration of VK and a screening test for VK deficiency are carried out in Japan. For the screening, the total activity of VK-dependent coagulation factors is measured using a commercial product, Normotest. This study was undertaken to clarify the importance of the following genetic and environmental factors on the coagulation status in one-month-old infants: two polymorphisms in the factor VII gene, -323P0/10 (a 10-bp insertion in the promoter region at position -323) and R353Q (the replacement of arginine [R] with glutamine [Q] at residue 353) and sex, age, gestational age, birth weight, and feeding regimen. Two hundred Japanese infants (34.6 +/- 4.0 days old) were screened for VK-dependent coagulation activity with Normotest and were genotyped for the two polymorphisms. Among the subjects screened, 18 infants (9%) carried the P10 allele and 26 (13%) carried the R353Q allele. Multiple regression analysis showed that the 10-bp inserted (P10) allele or the Q allele was associated with the lower coagulation activities. The coagulation activities for the R/Q genotype were significantly lower than those for the R/R genotype and those for the P0/P10 genotype were significantly lower than those for the P0/P0 genotype. Therefore, infants who carry the P10 allele or the Q allele show lower activity of VK-dependent coagulation factors. These infants may have a higher risk of VKDB manifestation.

Efficacy of warfarin reversal in orthopedic trauma surgery patients

OBJECTIVES

We determine the efficacy of active reversal of warfarin anticoagulation with intravenous vitamin K compared to withholding warfarin in patients requiring urgent orthopedic trauma surgery.

DESIGN

This was a prospective cohort with immediate prehypothesis consecutive retrospective comparative case series conducted at a level 1 university hospital trauma unit.

PATIENTS

Forty-eight consecutive patients between 1998 and 2004 in a study composed of a prospective cohort were compared with a retrospective consecutive case series of warfarinized orthopedic trauma patients requiring urgent surgery. The prospective arm directly followed the historic case series from which the hypothesis was generated.

INTERVENTION

Vitamin K administration.

MAIN OUTCOME MEASURES

Primary outcome was time to surgery. Secondary outcomes were problems with active reversal, length of time for warfarin stabilization after surgery, and complications.

RESULTS

The mean time to surgery in warfarinized patients not given vitamin K was 111.9 hours; in the intervention group, it was 67.4 hours, giving a mean difference of 44.5 hours (P = 0.01). Vitamin K reduced the international normalized ratio (INR) to less than 2.0 in 74% of patients within 24 hours. There were no complications of vitamin K administration. A dose of vitamin K costs approximately 1/1000 of a hospital bed day cost. A loading dose of warfarin on the second postoperative day took approximately 1 day longer to reach an INR of greater than 2.0 in the intervention patients than in those who had not been given vitamin K.

CONCLUSIONS

Warfarin reversal with vitamin K was successful and facilitated earlier surgery in all patients; the first dose was effective in approximately three quarters of patients. It is cost-effective, with no side effects caused in this study.

Dietary vitamin K intake and anticoagulation in elderly patients

PURPOSE OF REVIEW

Vitamin K is an essential co-factor for the synthesis of several coagulation factors. Oral anticoagulants competitively inhibit enzymes that participate in vitamin K metabolism. The purpose of this review is to evaluate the potential interaction of dietary vitamin K and coagulation stability, particularly in the elderly patient.

RECENT FINDINGS

Recent prospective evidences suggest that dietary vitamin K plays an essential role in anticoagulation stability. Vitamin K intake of more than 250 microg/day was shown to decrease warfarin sensitivity in anticoagulated patients consuming regular diets. In a randomized crossover study, brief periods of changes on vitamin K intake also had significant effects on coagulation parameters. Patients that were allocated to an 80% decrease of intake increased International Normalized Ratio (INR) by almost 30% 7 days after the intervention. Similarly, it was estimated by dietary records that for each increase in 100 microg of vitamin K intake, the INR would be reduced by 0.2. A recent study also demonstrated that over-the-counter multivitamin supplements contain enough vitamin K1 to significantly alter coagulation parameters.

SUMMARY

Contemporary data strengthen the concept that the interaction between dietary vitamin K and coumarin derivatives is clinically relevant and plays a major role in INR fluctuations in chronic anticoagulated patients.

Appraisal of current vitamin K dosing algorithms for the reversal of over-anticoagulation with warfarin: the need for a more tailored dosing regimen

Warfarin is the most commonly prescribed oral anticoagulant in the UK for the treatment and prevention of thromboembolic disorders. Vitamin K administration is an effective way of reversing excessive anticoagulation. Over-anticoagulated patients present with a wide range of international normalized ratio (INR) values and may respond differently to a fixed dose of vitamin K. Current dosing algorithms for vitamin K administration in the non-urgent treatment of over-anticoagulation do not take this variability in response into account. Consequently, over a third of over-anticoagulated patients still remain outside their target INR 24 h after treatment. Such patients are therefore prone to either haemorrhage (if the patient is still over-anticoagulated) or thromboembolism (if the INR reversal is over-corrected). A number of factors such as patient age, body weight, co-morbidity, frailty, warfarin daily dose and CYP2C9 and VKORC1 polymorphism could affect response to vitamin K and thus the rate and extent of INR reversal. There is a need for a more individualized approach to the reversal of over-anticoagulation in asymptomatic or mildly haemorrhagic patients in order to improve the safety of warfarin therapy.

Vitamin K prophylaxis for preterm infants: a randomized, controlled trial of 3 regimens

OBJECTIVE

Preterm infants may be at particular risk from either inadequate or excessive vitamin K prophylaxis. Our goal was to assess vitamin K status and metabolism in preterm infants after 3 regimens of prophylaxis.

METHODS

Infants <32 weeks' gestation were randomized to receive 0.5 mg (control) or 0.2 mg of vitamin K1 intramuscularly or 0.2 mg intravenously after delivery. Primary outcome measures were serum vitamin K1, its epoxide metabolite (vitamin K1 2,3-epoxide), and undercarboxylated prothrombin assessed at birth, 5 days, and after 2 weeks of full enteral feeds. Secondary outcome measures included prothrombin time and factor II concentrations.

RESULTS

On day 5, serum vitamin K1 concentrations in the 3 groups ranged widely (2.9-388.0 ng/mL) but were consistently higher than the adult range (0.15-1.55 ng/mL). Presence of vitamin K1 2,3-epoxide on day 5 was strongly associated with higher vitamin K1 bolus doses. Vitamin K1 2,3-epoxide was detected in 7 of 29 and 4 of 29 infants from the groups that received 0.5 mg intramuscularly and 0.2 mg intravenously, respectively, but in none of 32 infants from group that received 0.2 mg intramuscularly. After 2 weeks of full enteral feeding, serum vitamin K1 was lower in the infants who received 0.2 mg intravenously compared with the infants in the control group. Three infants from the 0.2-mg groups had undetectable serum vitamin K1 as early as the third postnatal week but without any evidence of even mild functional deficiency, as shown by their normal undercarboxylated prothrombin concentrations.

CONCLUSIONS

Vitamin K1 prophylaxis with 0.2 mg administered intramuscularly maintained adequate vitamin K status of preterm infants until a median age of 25 postnatal days and did not cause early vitamin K1 2,3-epoxide accumulation. In contrast, 0.2 mg administered intravenously and 0.5 mg administered intramuscularly led to vitamin K1 2,3-epoxide accumulation, possibly indicating overload of the immature liver. To protect against late vitamin K1 deficiency bleeding, breastfed preterm infants given a 0.2-mg dose of prophylaxis should receive additional supplementation when feeding has been established.

Vitamin K supplementation can improve stability of anticoagulation for patients with unexplained variability in response to warfarin

Patients receiving warfarin who have unstable control of anticoagulation have a significantly lower intake of dietary vitamin K compared with their stable counterparts. We hypothesized that supplementation with oral vitamin K would improve stability in patients with previously unstable control of anticoagulation. Seventy warfarin-treated patients with unstable anticoagulation control were randomly assigned in a double-blinded fashion to receive a daily amount of 150 mug oral vitamin K or placebo orally for 6 months. Measures of stability of anticoagulation control in the 6-month study period were compared with those in the 6 months immediately prior to it. Vitamin K supplementation resulted in a significantly greater decrease in standard deviation of international normalized ratio (INR) compared with placebo (-0.24 +/- 0.14 vs -0.11 +/- 0.18; P < .001) and a significantly greater increase in percentage time within target INR range (28% +/- 20% vs 15% +/- 20%; P < .01). Anticoagulation control improved in 33 of 35 patients receiving vitamin K supplementation; of these, 19 fulfilled our criteria for having stable control of anticoagulation. However, only 24 of 33 patients receiving placebo demonstrated some degree of improvement, with only 7 patients fulfilling the criteria for having stable control. Concomitant supplementation of vitamin K, perhaps through reducing the relative day-to-day variability in dietary vitamin K intake, can significantly improve anticoagulation control in patients with unexplained instability of response to warfarin.

Founder mutation Arg485Pro led to recurrent compound heterozygous GGCX genotypes in two German patients with VKCFD type 1

Congenital combined deficiency of the vitamin-K-dependent coagulation factors (VKCFD) represents a rare autosomal recessive inherited bleeding disorder caused by mutations in either the gamma-glutamyl carboxylase gene (VKCFD type 1) or the vitamin K epoxide reductase gene (VKCFD type 2). Four different mutations of the gamma-glutamyl carboxylase gene (GGCX) have so far been reported in three unrelated patients with VKCFD type 1. Here we report on a fourth patient who presented with two compound heterozygous missense mutations of the GGCX gene, His404Pro and Arg485Pro. The His404Pro mutation has not been described previously, while the Arg485Pro mutation has been reported in another compound heterozygous VKCFD type 1 patient from Germany. Most interestingly, haplotype analysis revealed that Arg485Pro is due to a founder mutation, suggesting that this mutation is present in the German population at some low frequency. The founder mutation explains that the only two compound heterozygous VKCFD type 1 patients known today originated from Germany.

[Late form of vitamin K deficiency bleeding. Description of four cases with various clinical picture and outcome]

Late form of vitamin K deficiency bleeding (VKDB) occurs in infants who received none, or inadequate vitamin K prophylaxis after birth. Exclusively breastfed infants are especially prone to development of this disease. We present 4 cases of late VKDB with different clinical picture and outcome. In two patients intracranial bleeding of variable magnitude was detected, in one, bleeding into pleural cavity and in the fourth severe bleeding from injection sites without internal haemorrhage. Diagnosis was based on the clinical picture with special emphasis on the child's past history and results of coagulation tests. Treatment consisted mainly of vitamin K administration and infusion of fresh frozen plasma. One patient developed severe and definite brain damage after intracranial bleeding, the second only a mild brain dysfunction, the remaining two infants recovered fully. These observations and literature data suggest that in exclusively breastfed infants who did not receive vitamin K after birth, late VKDB should be taken into account as a cause of haemorrhage with different localization and magnitude. There is a need for more emphasis on teaching of physicians about late VKDB and for parenteral vitamin K prophylaxis programme for all newborn infants.

[Nutritional care and management for osteoporosis]

A significant point of nutritional care and management for osteoporosis is that calcium and vitamin D are recommended to be actively administered on top of sufficient intake of energy and the other nutrients including protein. Daily intake of calcium and vitamin D is encouraged at least 800 mg and 10 to 20 microg, respectively. Calcium and vitamin D are also important for maximizing the effect of osteoporosis drug therapy. Supplement of calcium or vitamin D could be a supportive measure, when their necessary amount is difficult to be consumed.

Vitamin K suppresses lipopolysaccharide-induced inflammation in the rat

Vitamin K (K) is essential for blood coagulation and bone metabolism in mammals. K acts as a cofactor in the posttranslational synthesis of gamma-carboxyglutamic acid from glutamic acid residues. In addition to the liver and bone, K is found in the brain, heart, kidney and gonadal tissue. However, the physiological role of K in these various organs is not yet fully understood. It is likely that K has functions other than its role as a cofactor of protein gamma-glutamyl carboxylation. We used in this study the DNA microarray technique to identify the effect of K status on gene expression in the rat liver. The expression of genes involved in the acute inflammation response was enhanced in rats fed with a K-deficient diet relative to the control and K1-supplemented diet groups. Moreover, dietary supplementation with K1 suppressed the inflammation induced by lipopolysaccharide administration. These results indicate that orally administrated K1 suppressed inflammation in the rat.

Canine Intestinal Contents vs. Simulated Media for the Assessment of Solubility of Two Weak Bases in the Human Small Intestinal Contents

PURPOSE

This study was conducted to assess the relative usefulness of canine intestinal contents and simulated media in the prediction of solubility of two weak bases (dipyridamole and ketoconazole) in fasted and fed human intestinal aspirates that were collected under conditions simulating those in bioavailability/bioequivalence studies.

METHODS

After administration of 250 mL of water or 500 mL of Ensure plus [both containing 10 mg/mL polyethylene glycol (PEG) 4000 as nonabsorbable marker], intestinal aspirates were collected from the fourth part of the duodenum of 12 healthy adults and from the mid-jejunum of four Labradors. Pooled samples were analyzed for PEG, pH, buffer capacity, osmolality, surface tension, pepsin, total carbohydrates, total protein content, bile salts, phospholipids, and neutral lipids. The shake-flask method was used to measure the solubility of dipyridamole and ketoconazole in pooled human and canine intestinal contents and in fasted-state-simulating intestinal fluid (FaSSIF) and fed-state-simulating intestinal fluid (FeSSIF) containing various bile salts and pH-buffering agents.

RESULTS

For both compounds, solubility in canine contents may be predictive of human intralumenal solubility in the fasting state but not in the fed state. The poor agreement of results in canine and human aspirates can be attributed to the higher bile salt content in canine bile. Solubility in FaSSIF containing a mixture of bile salts from crude bile predicted satisfactorily the intralumenal solubility of both drugs in the fasted state in humans. Solubility in FeSSIF, regardless of the identity of bile salts or of the buffering species, deviated from intralumenal values in the fed human aspirates by up to 40%. This was attributed to the lack of lipolytic products in FeSSIF, the higher bile salt content of FeSSIF, and the lower pH of FeSSIF.

CONCLUSIONS

FaSSIF containing a mixture of bile salts from crude bile, and FeSSIF containing lipolytic products and, perhaps, having lower bile salt content but slightly higher pH, should be more useful than canine intestinal aspirates for predicting intralumenal solubilities in humans.

Menadione is a metabolite of oral vitamin K

Phylloquinone is converted into menaquinone-4 and accumulates in extrahepatic tissues. Neither the route nor the function of the conversion is known. One possible metabolic route might be the release of menadione from phylloquinone by catabolic activity. In the present study we explored the presence of menadione in urine and the effect of vitamin K intake on its excretion. Menadione in urine was analysed by HPLC assay with fluorescence detection. Urine from healthy male volunteers was collected before and after administration of a single dose of K vitamins. Basal menadione excretion in non-supplemented subjects (n 6) was 5.4 (sd 3.2) microg/d. Urinary menadione excretion increased greatly after oral intake of the K vitamins, phylloquinone and menaquinone-4 and -7. This effect was apparent within 1-2 h and peaked at about 3 h after intake. Amounts of menadione excreted in 24 h after vitamin K intake ranged, on a molar basis, from 1 to 5 % of the administered dose, indicating that about 5-25 % of the ingested K vitamins had been catabolized to menadione. Menadione excretion was not enhanced by phylloquinone administered subcutaneously or by 2',3'-dihydrophylloquinone administered orally. In archived samples from a depletion/repletion study (Booth et al. (2001) Am J Clin Nutr 74, 783-790), urinary menadione excretion mirrored dietary phylloquinone intake. The present study shows that menadione is a catabolic product of K vitamins formed after oral intake. The rapid appearance in urine after oral but not subcutaneous administration suggests that catabolism occurs during intestinal absorption. The observations make it likely that part of the menaquinone-4 in tissues results from uptake and prenylation of circulating menadione.

[The preparation of a patient with long-term anticoagulant cumarin treatment for invasive surgery]

Coumarins belong to drugs widely used and the spectrum of their use is going to grow. From this point of view and/or because the coumarins are adminstrated in patients who are treated for the other diseases--medical or surgical--at the same time, it is necessary to modify, interrupt or replace peroral anticoagulant treatment in the dependence on various aspects. It requires to compound different algorithms for given situations solution. It is always to decide, if the situation is imperative from the view of solution planed, what risk brings proposed treatment and what is the risk of anticoagulant treatment modification.

Dietary Vitamin K Variability Affects International Normalized Ratio (INR) Coagulation Indices

Background: Changes in daily vitamin K intake may contribute to marked variations in the International Normalized Ratio (INR) coagulation index in patients receiving oral warfarin anticoagulant therapy, with potentially serious adverse outcomes. Thus, patients receiving warfarin therapy are routinely counseled regarding this drug-nutrient interaction and are instructed to maintain consistent vitamin K intakes, though little quantitative information about this relationship is available. Objective: To determine the quantitative impact of variability in dietary vitamin K1 (phylloquinone) intake, assessed by a validated patient self-monitoring instrument, on weekly INR in patients receiving warfarin anticoagulant therapy. Methods: A prospective dietary assessment study was conducted at the Massachusetts General Hospital in Boston. Sixty outpatients (37 males and 23 females) were selected with a mean age 60.3 ± 16.8 years, who began oral warfarin anticoagulant therapy within 14 days prior to their first clinic visit to an outpatient anticoagulation therapy unit. Exclusion criteria included more than 2 drinks of alcohol per day, inability to speak English, and concurrent disease states affecting warfarin therapy such as liver disease and terminal illness. Over the five-week study period, participants recorded daily intakes in specified amounts of all food items appearing on a validated dietary self-assessment tool. Concomitant use of prescription and/or non-prescription medications was also obtained. Concurrent daily warfarin dose and adherence to the drug regimen, concomitant use of prescription and/or non-prescription medications known to interact with warfarin, and weekly INR were obtained. Week-to-week changes in vitamin K intake, warfarin dose, and INR were determined and cross-correlated. Results: Forty-three patients (28 males and 15 females) completed the study and 17 dropped out. Pearson’s correlation coefficient revealed the variability in INR and changes in vitamin K intake were inversely correlated (r = –0.600, p < 0.01). Multiple regression analysis (r = 0.848) indicated that a weekly change of 714 mug dietary vitamin K significantly altered weekly INR by 1 unit (p < 0.01) and a weekly change of 14.5 mg warfarin significantly altered weekly INR by 1 unit (p < 0.01) after adjustment for age, sex, weight, height, and concomitant use of medications known to interact with warfarin. Conclusions: Patients taking warfarin and consuming markedly changing amounts of vitamin K may have a variable weekly INR with potentially unstable anticoagulant outcomes.