Effect of 200μG/day of vitamin K1 on the variability of anticoagulation control in patients on warfarin: a randomized controlled trial

Comparison of the effects of different treatment protocols on mortality in patients presenting with an INR≥10 due to warfarin-associated over-anticoagulation

Aim

One of the most anticipated adverse effects of warfarin is over-anticoagulation. There is little to no evidence on the treatment that should be administered in patients with an international normalized ratio (INR)≥10. The primary outcome of this study is to analyze the effects of various treatments on 30-day mortality in patients with INR≥10 and without major bleeding on 30-day all-cause mortality. The secondary outcome is to propose a model that predicts 30-day all-cause mortality in the same patient group.

Methods

Patients older than 18 years of age using warfarin and who had an INR≥10 were included in this retrospective cohort study. Patients with major bleeding on admission were excluded. Patients treated with only cessation of warfarin were named as "Group-1", patients who were treated with vitamin-K in addition to cessation of warfarin were named as "Group-2", and patients who were treated with cessation of warfarin and vitamin-K and fresh frozen plasma or prothrombin complex concentrate were named as "Group-3".

Results

190 patients were included in the analysis. Seven (38.9%) patients in the first group, 3 (8.6%) in the second group, and 21 (15.3%) in the third group died within 30-days(p=0.015). In the post-hoc analysis, the difference between Group-1 and Group-2 was found to be significant(p=0.036, OR:0.147, 95%CI=0.032 to 0.671).The performance of the model in predicting 30-day all-cause mortality was high (AUC=0.818 (95%CI = 0.716 to 0.920) and found to be compatible with the validation dataset 0.806 (95%CI = 0.631 to 0.981). Administration of vitamin K in addition to the cessation of warfarin was found to be a strong contributor to the model and an independent predictor of survival within 30 days(p=0.006).

Conclusions

Until randomized controlled studies are conducted, it may be reasonable to administer vitamin-K in addition to cessation of warfarin in non-bleeding patients with INR≥10.

US Pharmacopeial Convention safety evaluation of menaquinone-7, a form of vitamin K

Vitamin K plays important biological roles in maintaining normal blood coagulation, bone mineralization, soft tissue physiology, and neurological development. Menaquinone-7 is a form of vitamin K2 that occurs naturally in some animal-derived and fermented foods. It is also available as an ingredient of dietary supplements. Menaquinone-7 has greater bioavailability than other forms of vitamin K, which has led to increasing sales and use of menaquinone-7 supplements. This special article reviews the chemistry, nomenclature, dietary sources, intake levels, and pharmacokinetics of menaquinones, along with the nonclinical toxicity data available and the data on clinical outcomes related to safety (adverse events). In conclusion, the data reviewed indicate that menaquinone-7, when ingested as a dietary supplement, is not associated with any serious risk to health or with other public health concerns. On the basis of this conclusion, US Pharmacopeia monographs have been developed to establish quality standards for menaquinone-7 as a dietary ingredient and as a dietary supplement in various dosage forms.

Guidance for the practical management of warfarin therapy in the treatment of venous thromboembolism

Venous thromboembolism (VTE) is a serious and often fatal medical condition with an increasing incidence. The treatment of VTE is undergoing tremendous changes with the introduction of the new direct oral anticoagulants and clinicians need to understand new treatment paradigms. This article, initiated by the Anticoagulation Forum, provides clinical guidance based on existing guidelines and consensus expert opinion where guidelines are lacking. Well-managed warfarin therapy remains an important anticoagulant option and it is hoped that anticoagulation providers will find the guidance contained in this article increases their ability to achieve optimal outcomes for their patients with VTE Pivotal practical questions pertaining to this topic were developed by consensus of the authors and were derived from evidence-based consensus statements whenever possible. The medical literature was reviewed and summarized using guidance statements that reflect the consensus opinion(s) of all authors and the endorsement of the Anticoagulation Forum’s Board of Directors. In an effort to provide practical and implementable information about VTE and its treatment, guidance statements pertaining to choosing good candidates for warfarin therapy, warfarin initiation, optimizing warfarin control, invasive procedure management, excessive anticoagulation, subtherapeutic anticoagulation, drug interactions, switching between anticoagulants, and care transitions are provided.

The effect of low-dose oral vitamin K supplementation on INR stability in patients receiving warfarin. A randomised trial

The anticoagulant effect of warfarin is influenced by variations in vitamin K intake. Concomitant use of daily low-dose oral vitamin K (LDVK) and warfarin may improve INR stability. We hypothesise that administration of LDVK improves INR control. To test this hypothesis we performed a multi-centre, placebo-controlled, randomised trial conducted at four university-affiliated hospitals in Canada. Patients on chronic warfarin therapy received oral vitamin K 150 mcg daily or a matching placebo for a total of six months after a one-month run in period. The primary outcome was a comparison of mean time in therapeutic range (TTR) in LDVK and placebo group during a six-month-period. The secondary outcome was number of INR excursions <1.5 or >4.5. There was no significant difference in the final TTR between the two groups (65.1 % vs 66 %, p =0.8). Mean TTR in both LDVK and placebo groups were statistically increased compared with prior to the study. The number of INR excursions were significantly decreased in the LDVK group (9.4 % and 5.4 %, absolute difference [pre- minus post-] = 4 %, 95 % CI, 2 to 6 %, p-value <0.001). We conclude that LDVK administration did not increase mean TTR, but did decrease the number of INR excursions. The observed improvement in mean TTR in both groups suggests that more attentive monitoring of warfarin therapy, rather than LDVK, was responsible for the improvement in TTR observed. The reduced excursions suggest that LDVK did reduce extreme INR variation. The study is registered at www.ClinicalTrial.gov# NCT00990158.

[A Systematic Review of the Acceptable Intake Level of Vitamin K among Warfarin Users]

The interaction of warfarin and vitamin K is a clinically significant issue. This study investigated the acceptable intake level of vitamin K among warfarin users by means of a systematic review. We searched two databases (PubMed and "Igaku chuo zasshi")for articles about adverse events arising from interaction of warfarin and vitamin K, published until October 2014. Of 1,310 citations retrieved, 16 studies met the selection criteria for examination of the upper limit, and 6 studies dealt with amounts below the limit. The intake of vitamin K in warfarin patients was acceptable in the range of 25-325 μg/day, with a maximum daily variation of 292 μg, and a value of 150 μg/day seemed optimum. When these results were applied to usual foods, except for dietary supplements or health foods, the only prohibited foods were fermented soybean (natto) and foods containing it, while green leafy vegetables could be acceptable if their intake is limited.

Avoidance of Vitamin K-Rich Foods Is Common among Warfarin Users and Translates into Lower Usual Vitamin K Intakes

BACKGROUND

Warfarin users should aim for stable daily vitamin K intakes. However, some studies report that patients are often advised to avoid eating green vegetables. Whether this advice impacts vitamin K intakes is unknown.

OBJECTIVE

Our aim was to describe the nature and sources of vitamin K-related dietary recommendations that patients received at the initiation of warfarin therapy, assess their adherence to these recommendations, and examine whether usual vitamin K intakes vary according to these recommendations.

DESIGN

We conducted a retrospective cohort study with patients enrolled in the Québec Warfarin Cohort Study. Patients were asked to report dietary recommendations they had received at warfarin initiation and their adherence to these recommendations. Usual vitamin K intakes were assessed using a validated semi-quantitative food frequency questionnaire.

PARTICIPANTS/SETTING

Three hundred seventeen patients aged 36 to 97 years who initiated warfarin between 2011 and 2012 and were treated for 12 months or longer with a target international normalized ratio range of 2.0 to 3.0 or 2.5 to 3.5.

STATISTICAL ANALYSES PERFORMED

Patients were classified according to vitamin K-related recommendations reported: limit or avoid vitamin K-rich foods; aim for stable consumption of vitamin K-rich foods; or no vitamin K-related advice. A one-way analysis of covariance was used to compare mean usual vitamin K intakes between patients after adjustment for covariates.

RESULTS

Most patients (68%) reported being advised to limit or avoid vitamin K-rich foods, particularly green vegetables, 10% reported being advised to aim for stable consumption of vitamin K-rich foods, and 22% did not recall receiving any vitamin K-related recommendation. Mean usual vitamin K intakes of patients adhering to the recommendation to limit or avoid vitamin K-rich foods was 35% to 46% lower than those of other patients (P<0.001), a difference resulting almost entirely (82%) from a lower consumption of green vegetables.

CONCLUSIONS

In contrast with current dietary recommendation, most warfarin users reported avoiding vitamin K-rich foods, which translated into lower usual vitamin K intakes.