Vitamin K intake, body mass index and warfarin maintenance dose

Impact of body mass index on 90-day warfarin requirements: a retrospective chart review

Background:

Rates of obesity continue to rise worldwide as evidenced in the 2017 Centers for Disease Control and Prevention (CDC) report that indicated over 35% of United States (US) citizens are obese, with Louisiana ranked as the fifth most obese state in America. Since large clinical trials tend to exclude obese patients, health care providers are faced with concerns of under- or overdosing these patients on warfarin.

Methods:

This retrospective chart review evaluated patients who reported to a community anticoagulation clinic for warfarin management between 1 June 2017 and 30 September 2017. Along with baseline demographics, chronic use of drugs that have clinically significant interactions with warfarin, social activity such as tobacco use and alcohol consumption, were collected. Body mass indexes (BMI) were collected and categorized according to the World Health Organization definitions as follows: Normal (BMI 18–24.9 kg/m²), Overweight (25–29.9 kg/m²), Obesity Class I (30–34.9 kg/m²), Obesity Class II (35–39.9 kg/m²), Obesity Class III (⩾40 kg/m²). The primary outcome was the mean 90-day warfarin dose required to maintain “intermediate control” or “good control” of international normalized ratio (INR), stratified by BMI classifications. The secondary outcome was the time in therapeutic range (TTR) stratified by BMI classifications.

Results:

A total of 433 patient encounters were included in this study. There was a total of 43 encounters in the Normal BMI category, 111 Overweight encounters, 135 Obesity Class I encounters, 45 Obesity Class II encounters, and 99 Obesity Class III encounters. Approximately 63% of the study population were male, and over 90% the patients were African American. The Obesity Class I and Obesity Class II class required an average of 11.47 mg and 17.10 mg more warfarin, respectively, to maintain a therapeutic INR when compared with the Normal BMI category. These findings were statistically significant with p values of 0.007 and <0.001, respectively. Additionally, upon comparing the Overweight BMI category with the Obesity Class II category, there was a mean warfarin dose difference of 11.22 mg (p = 0.010) more in Obesity Class II encounters to maintain a therapeutic INR. In the secondary analysis of TTR, Overweight category encounters had the highest TTR, whereas encounters in the Normal BMI category had the lowest TTR.

Conclusion:

As BMI increases, there is an increased chronic warfarin requirement to maintain “intermediate control” or “good control” of INR between 2 and 3 in an ambulatory care setting.

Comparison of Two Different Techniques Of Warfarin Dosing Determination - A Chemometrics Study

A high prevalence of genetic polymorphisms increases sensitivity to warfarin therapy. In this study, we investigated 47 patients with effective long-term therapy by warfarin well-controlled by monitoring of International Normalised Ratio (INR). All patients were tested for gene polymorphisms VKORC1, CYP2C9*C2, and CYP2C9*C3, which were used for a dose calculation employing a program www.WarfarinDosing.org. The main goal was to investigate whether the warfarin doses determined by INR are in accordance with the doses calculated according to the pharmacogenetic algorithm. For this purpose, several chemometric tools, namely principal component analysis, cluster analysis, correlation analysis, correspondence analysis, Passing-Bablock regression, Bland-Altman method, descriptive statistics, and ANOVA were used. We also analysed the relationship between the dose of warfarin determined by INR and several constitutional and genetic factors. Statistically significant association between clinically optimized warfarin dose and indication for the treatment, age, and warfarin sensitivity determined by VKORC1, CYP2C9 gene polymorphisms were confirmed. Finally, we confirmed a good concordance between the INR determined warfarin doses and pharmacogenetic approach.

Evaluation of the impact of body mass index on warfarin requirements in hospitalized patients

BACKGROUND

Despite well established empiric dose adjustments for drug and disease-state interactions, the impact of body mass index (BM) on warfarin remains unclear. The objective of this study is to evaluate warfarin requirements in hospitalized patients, stratified by BMI.

METHODS

This retrospective review included two cohorts of patients: cohort A (patients admitted with a therapeutic international normalized ratio (INR)) and cohort B (newly initiated on warfarin during hospitalization). Exclusion criteria included: age under 18 years, pregnancy, INR (goal 2.5-3.5), and warfarin thromboprophylaxis post orthopedic surgery. The primary outcome was mean total weekly dose (TWD) of warfarin based on weight classification: underweight (BMI <18 kg/m²), normal/overweight (BMI 18-29.9 kg/m²), obese (BMI 30-39.9 kg/m²), and morbidly obese (BMI ⩾ 40 kg/m²). Data were extracted from two community hospitals in reverse chronologic order during July 2015-June 2013 until both study institutions evaluated 100 patients per cohort in each BMI classification or until all patients had been evaluated within the prespecified timeframe.

RESULTS

A total of 585 patients were included in cohort A (26 underweight, 200 normal/overweight, 200 obese, 159 morbidly obese). There was a statistically significant difference in TWD as determined by one-way analysis of variance ( p < 0.05). A Tukey post hoc test revealed a statistically significantly higher TWD in morbidly obese (41.5 mg) compared with underweight (25.6 mg, p < 0.05), normal/overweight (28.8 mg, p < 0.05) and obese patients (32.4 mg, p < 0.05). In cohort B, 379 patients were evaluated (9 underweight, 166 normal/overweight, 152 obese, 52 morbidly obese). Overall, 191 patients had a therapeutic INR on discharge (88.9% underweight, 52.4% normal/overweight, 44.1% obese, 55.8% morbidly obese, p = 0.035). Of those, there was a statistically significant difference in TWD ( p = 0.021) with a higher TWD in the morbidly obese (41 mg) compared with underweight patients (24.4 mg, p = 0.017).

CONCLUSIONS

Based on the results of this study, morbidly obese patients may require higher TWD to obtain and maintain a therapeutic INR.

Effects of VKORC1 Genetic Polymorphisms on Warfarin Maintenance Dose Requirement in a Chinese Han Population

Background

VKORC1 is reported to be capable of treating several diseases with thrombotic risk, such as cardiac valve replacement. Some single-nucleotide polymorphisms (SNPs) in VKORC1 are documented to be associated with clinical differences in warfarin maintenance dose. This study explored the correlations of VKORC1–1639 G/A, 1173 C/T and 497 T/G genetic polymorphisms with warfarin maintenance dose requirement in patients undergoing cardiac valve replacement.

Material/Methods

A total of 298 patients undergoing cardiac valve replacement were recruited. During follow-up, clinical data were recorded. Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method was applied to detect VKORC1–1639 G/A, 1173 C/T and 497 T/G polymorphisms, and genotypes were analyzed.

Results

Correlations between warfarin maintenance dose and baseline characteristics revealed statistical significances of age, gender and operation methods with warfarin maintenance dose (all P<0.05). Warfarin maintenance dose in VKORC1–1639 G/A AG + GG carriers was obviously higher than in AA carriers (P<0.001). As compared with patients with TT genotype in VKORC1 1173 C/T, warfarin maintenance dose was apparently higher in patients with CT genotype (P<0.001). Linear regression analysis revealed that gender, operation method, method for heart valve replacement, as well as VKORC1–1639 G/A and 1173 C/T gene polymorphisms were significantly related to warfarin maintenance dose (all P<0.05).

Conclusions

VKORC1 gene polymorphisms are key genetic factors to affect individual differences in warfarin maintenance dose in patients undergoing cardiac valve replacement; meanwhile, gender, operation method and method for heart valve replacement might also be correlate with warfarin maintenance dose.