Warfarin

Warfarin(WARF42) is an anticoagulant drug normally used to prevent blood clot formation as well as migration. Target: Others Warfarin is an anticoagulant normally used in the prevention of thrombosis and thromboembolism, the formation of blood clots in the blood vessels and their migration elsewhere in the body respectively. Warfarin and related 4-hydroxycoumarin-containing molecules decrease blood coagulation by inhibiting vitamin K epoxide reductase, an enzyme that recycles oxidized vitamin K1 to its reduced form after it has participated in the carboxylation of several blood coagulation proteins, mainly prothrombin and factor VII. Despite being labeled a vitamin K antagonist, warfarin does not antagonize the action of vitamin K1, but rather antagonizes vitamin K1 recycling, depleting active vitamin K1 [1, 2].

References:
[1]. Ansell, J., et al., Pharmacology and management of the vitamin K antagonists: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines (8th Edition). Chest, 2008. 133(6 Suppl): p. 160S-198S. [2]. http://en.wikipedia.org/wiki/Warfarin

Volume and Characteristics of Intracerebral Hemorrhage with Direct Oral Anticoagulants in Comparison with Warfarin.[Pubmed:28376486]

Cerebrovasc Dis Extra. 2017;7(1):62-71.

BACKGROUND: Patients undergoing anticoagulation therapy often experience intracerebral hemorrhages (ICHs), and Warfarin in particular is known to increase hematoma expansion in ICHs, which results in a poor outcome. Recent studies reported that, in comparison with Warfarin, direct oral anticoagulants (DOACs) cause fewer ICHs with better functional outcome. However, since it is still unknown whether DOACs are associated with a smaller hematoma volume of ICHs, we aimed to compare the volume, hematoma expansion, and outcomes associated with ICHs treated with DOACs and Warfarin. METHODS: We performed a prospective multicenter cross-sectional study. The subjects included patients with acute ICHs who received either DOACs or Warfarin. We evaluated the clinical characteristics, and measured initial and follow-up ICH volumes. The volume of ICHs and hematoma expansion were compared between the DOAC and Warfarin groups. Mortality and modified Rankin score at discharge were evaluated as outcomes. RESULTS: There were 18 patients in the DOAC group and 71 in the Warfarin group. The baseline characteristics were similar between the 2 groups. Initial median hematoma volume of ICHs in the DOAC group was significantly lower than that in the Warfarin group (6.2 vs. 24.2 mL, respectively; p = 0.04). In cases involving follow-up computed tomography scanning, the median hematoma volume of ICHs at follow-up was lower in the DOAC group than in the Warfarin group (initial: DOACs 4.4 vs. Warfarin 13.5 mL; follow-up: 5.0 vs. 18.4 mL, respectively; p = 0.05). Further, the hematoma in ICHs associated with DOACs did not expand. Although the mortality of ICHs associated with DOACs (11%) was lower than that associated with Warfarin (24%), this difference was not statistically significant. The univariate analysis showed that the anticoagulant type (DOACs vs. Warfarin) and sex (male vs. female) were associated with ICH volume. The multivariable linear regression showed that the use of DOACs (compared to Warfarin; beta: -0.23, p = 0.03) and female sex (compared to male; beta: -0.25, p = 0.02) were associated with a small hematoma volume. CONCLUSIONS: Based on the results of the present study, in terms of the risks associated with ICHs, the use of DOACs appears to be safer than Warfarin for anticoagulation therapy. Further studies are required to validate these findings..

The Cost Differential Between Warfarin Versus Aspirin Treatment After a Fontan Procedure.[Pubmed:28372885]

Heart Lung Circ. 2017 Aug;26(8):e44-e47.

BACKGROUND: The use of aspirin versus Warfarin for treatment of patients after a Fontan procedure remains contentious. Current preference-based models of treatment across Australia and New Zealand show variation in care that is unlikely to reflect patient differences and/or clinical risk. METHODS: We combine data from the Australian and New Zealand Fontan Registry and a home INR (International Normalised Ratio) monitoring program (HINRMP) from the Royal Children's Hospital (RCH) Melbourne, to estimate the cost difference for Fontan recipients receiving aspirin versus Warfarin for 2015. We adopt a societal perspective to costing which includes cost to the health system (e.g. medical consults, pathology tests) and costs to patients and carers (e.g. travel and time), but excludes costs of adverse events. Costs are presented in Australian 2015 dollars; any costs from previous years have been inflated using appropriate rates from the Australian Bureau of Statistics. RESULTS: We find that Warfarin patients face additional costs of $825 per annum, with the majority ($584 or 71%) of those borne by the patient or family. If aspirin is as clinically as effective as Warfarin, Fontan recipients could be enjoying far less costly, invasive and time-consuming treatment. While achieving such clinical consensus can be difficult, economics shows us that there are large costs associated with a failure to achieve it.

Integrating In Vitro, Modeling, and In Vivo Approaches to Investigate Warfarin Bioequivalence.[Pubmed:28379643]

CPT Pharmacometrics Syst Pharmacol. 2017 Aug;6(8):523-531.

We demonstrate the use of modeling and simulation to investigate bioequivalence (BE) concerns raised about generic Warfarin products. To test the hypothesis that the loss of isopropyl alcohol and slow dissolution in acidic pH has significant impact on the pharmacokinetics of Warfarin sodium tablets, we conducted physiologically based pharmacokinetic absorption modeling and simulation using formulation factors or in vitro dissolution profiles as input parameters. Sensitivity analyses indicated that Warfarin pharmacokinetics was not sensitive to solubility, particle size, density, or dissolution rate in pH 4.5, but was affected by dissolution rate in pH 6.8 and potency. Virtual BE studies suggested that stressed Warfarin sodium tablets with slow dissolution rate in pH 4.5 but having similar dissolution rate in pH 6.8 would be bioequivalent to the unstressed Warfarin sodium tablets. A four-way, crossover, single-dose BE study in healthy subjects was conducted to test the same hypothesis and confirmed the simulation conclusion.

Bioequivalence Study of Warfarin in Healthy Chinese Volunteers With a Validated High-Performance Liquid Chromatography-Mass Spectrometry Method.[Pubmed:28371488]

Clin Pharmacol Drug Dev. 2018 Mar;7(3):256-262.

This study was designed to investigate the pharmacokinetics of an innovative film-coated Warfarin sodium tablet and to compare it with the marketed sugar-coated Warfarin sodium tablet in humans. A single-dose, open-label, randomized, two-way crossover study was performed in 24 healthy Chinese male volunteers. They were administered 2.5 mg of innovative film-coated Warfarin sodium tablets or the marketed sugar-coated Warfarin sodium tablets. Blood samples were collected at different time points after dosing for investigation of the pharmacokinetics of Warfarin in human plasma. A sensitive liquid chromatography mass spectrometry method was established to determine Warfarin in plasma. Drug and Statistics 2.1.1 was applied to calculate the pharmacokinetics parameters. The main pharmacokinetic parameters for film-coated and sugar-coated Warfarin were the following: t(1/2) , 103.5 +/- 18.8 and 105.8 +/- 21.3 hours; Tmax , 0.7 +/- 0.5 and 1.3 +/- 0.8 hours; Cmax , 347.8 +/- 74.8 and 322.9 +/- 75.7 ng/mL; AUC0 approximately 360 , 16,024.2 +/- 3713.9 and 15,586.6 +/- 3477.0 ng.mL(-1) .h; AUC0 approximately infinity , 17,335.7 +/- 4089.1 and 16,912.0 +/- 3911.2 ng.mL(-1) .h, respectively. The human pharmacokinetics of film-coated and sugar-coated Warfarin were slightly different. The oral absorption and bioavailability of innovative film-coated Warfarin were slightly higher than those of the sugar-coated Warfarin. This study is vital to clinical usage of Warfarin not only because of the pharmacokinetic parameters of the 2 pharmaceutical dosage forms of Warfarin but also to obtain data on the prevalence of CYP2C9 and VKORC1 genes and their influence on the concentration of Warfarin.

Warfarin (WARF-42; Athrombine-K) is a potent anticoagulant agent and a vitamin K1 recycling antagonist to deplete active vitamin K1. Warfarin decreases blood coagulation and prevents blood clot formation by inhibiting vitamin K epoxide reductase.

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