Pharmacokinetic and pharmacodynamic interactions of aspirin with warfarin in beagle dogs

The influence of Javanese turmeric (Curcuma xanthorrhiza) on the pharmacokinetics of warfarin in rats with single and multiple-dose studies

CONTEXT

Co-administration between warfarin (WF) and Curcuma xanthorrhiza Roxb. (Zingiberaceae) (CX) is found in Indonesian patients and need to be evaluated.

OBJECTIVE

This study assesses the effect of concomitant administration of CX extract on the pharmacokinetics of WF in rats.

MATERIALS AND METHODS

Wistar rats were divided into 4 groups (n = 6) and administered with 2% Pulvis Gummi Arabicum (PGA, control), fluconazole (FZ, 6 mg/kg), CX-1 (6 mg/kg) or CX-2 (18 mg/kg BW) for 7 days. For the single-dose study, at the 8th day, WF (1 mg/kg) was administered to all groups and blood samples were taken from 0.25 to 72 h. For the multiple-dose study, daily dose of WF was administered to all groups of rats and at the 7th to 9th day, the rats were treated with PGA, CX-1, CX-2 and FZ. Blood samples were withdrawn daily at 4 h after administration of WF from the 1st to 11th day.

RESULTS

The area under the curve (AUC) of R- and S-WF in the CX-2 group was a significantly higher value compared to the control (77.54 vs. 35.27 mg.h/L for R-WF and 316.26 vs. 40.16 mg.h/L for S-WF; p < 0.05; Kruskal-Wallis method). The CX-2 administration also caused the increasing in the concentration level of R-WF (16%) and S-WF (27%) from the 7th to 9th day of administration.

DISCUSSION AND CONCLUSIONS

The CX administration in a higher dose caused alteration on WF pharmacokinetics suggesting the need for clinical evaluation of the interaction between CX and WF.

Influence of glycyrrhetinic acid on the pharmacokinetics of warfarin in rats

1. Combination of different drugs has been widely applied in clinics in China. Both glycyrrhetinic acid (GA) and warfarin possess various pharmacological activities, the co-administration of them is becoming popular. However, the herb-drug interaction between GA and warfarin is still unknown.2. The herb-drug interaction between GA and warfarin in vivo and in vitro was studied, to clarify the effect of GA on the pharmacokinetics of warfarin and its main mechanism.3. The pharmacokinetics of intragastric administered warfarin (0.5 mg/kg) with or without GA pretreatment (100 mg/kg/day, 7 days) were investigated. The rat liver microsomes incubation systems were used to study the effect of GA on the metabolic stability of warfarin and support the in vivo pharmacokinetic data.4. The pharmacokinetic results indicated that co-administration of GA could increase the systemic exposure of warfarin, including area under the curve (48.87 ± 2.89 µg·h·mL^-1 without GA versus 58.63 ± 1.90 µg·h·mL^-1 with GA), maximum plasma concentration and t_1/2. The metabolic stability of warfarin increased from 23.8 ± 5.9 to 41.4 ± 7.1 min with the pretreatment of GA.5. These results indicated that GA could change the pharmacokinetic profile of warfarin. The metabolism of warfarin was slowed down in rat liver and the systemic exposure increased by GA, via inhibiting the activity of CYP3A4.

American College of Veterinary Emergency and Critical Care (ACVECC) Consensus on the Rational Use of Antithrombotics in Veterinary Critical Care (CURATIVE) guidelines: Small animal

OBJECTIVES

To systematically review available evidence and establish guidelines related to the risk of developing thrombosis and the management of small animals with antithrombotics.

DESIGN

Standardized, systematic evaluation of the literature (identified by searching Medline via PubMed and CAB abstracts) was carried out in 5 domains (Defining populations at risk; Defining rational therapeutic use; Defining evidence-based protocols; Refining and monitoring antithrombotic therapies; and Discontinuing antithrombotic therapies). Evidence evaluation was carried out using Population, Intervention, Comparison, Outcome generated within each domain questions to address specific aims. This was followed by categorization of relevant articles according to level of evidence and quality (Good, Fair, or Poor). Synthesis of these data led to the development of a series of statements. Consensus on the final guidelines was achieved via Delphi-style surveys. Draft recommendations were presented at 2 international veterinary conferences and made available for community assessment, review, and comment prior to final revisions and publication.

SETTINGS

Academic and referral veterinary medical centers.

RESULTS

Over 500 studies were reviewed in detail. Worksheets from all 5 domains generated 59 statements with 83 guideline recommendations that were refined during 3 rounds of Delphi surveys. A high degree of consensus was reached across all guideline recommendations.

CONCLUSIONS

Overall, systematic evidence evaluations yielded more than 80 recommendations for the treatment of small animals with or at risk of developing thrombosis. Numerous significant knowledge gaps were highlighted by the evidence reviews undertaken, indicating the need for substantial additional research in this field.

Consensus on the Rational Use of Antithrombotics in Veterinary Critical Care (CURATIVE): Domain 3-Defining antithrombotic protocols

OBJECTIVES

To systematically examine the evidence for use of a specific protocol (dose, frequency, route) of selected antithrombotic drugs, in comparisons to no therapy or to other antithrombotic therapies, to reduce the risk of complications or improve outcomes in dogs and cats at risk for thrombosis.

DESIGN

Standardized, systematic evaluation of the literature, categorization of relevant articles according to level of evidence (LOE) and quality (Good, Fair, or Poor), and development of consensus on conclusions via a Delphi-style survey for application of the concepts to clinical practice.

SETTINGS

Academic and referral veterinary medical centers.

RESULTS

Databases searched included Medline via PubMed and CAB abstracts. Eight different antithrombotic drugs were investigated using a standardized Patient, Intervention, Comparison, Outcome (PICO) question format both for dogs and cats, including aspirin, clopidogrel, warfarin, unfractionated heparin (UFH), dalteparin, enoxaparin, fondaparinux, and rivaroxaban, generating a total of 16 worksheets. Most studies identified were experimental controlled laboratory studies in companion animals (LOE 3) with only four randomized controlled clinical trials in companion animals (LOE 1).

CONCLUSIONS

Overall, evidence-based recommendations concerning specific protocols could not be formulated for most antithrombotic drugs evaluated, either because of the wide range of dosage reported (eg, aspirin in dogs) or the lack of evidence in the current literature. However, clopidogrel administration in dogs and cats at risk of arterial thrombosis, notably in cats at risk of cardiogenic thromboembolism, is supported by the literature, and specific protocols were recommended. Comparably, aspirin should not be used as a sole antithrombotic in cats with cardiomyopathy. Using the available safety profile information contained in the literature, the panel reached consensus on suggested dosage schemes for most antithrombotics. Significant knowledge gaps were highlighted, which will hopefully drive novel research.

Effects of Teicoplanin on the PT-INR Controlled by Warfarin in Infection Patients

Warfarin (WF) shows a number of interactions with other drugs, which alter its anticoagulant effects. The albumin binding interaction is one such pharmacokinetic mechanism of drug interaction with WF, which induces a rise in the free WF concentration and thus increases the risk of WF toxicity. Teicoplanin (TEIC) is an anti-methicillin-resistant Staphylococcus aureus drug, which also binds strongly to albumin in the plasma. Therefore, co-administration of TEIC may displace WF from the albumin binding site, and possibly result in a toxicity. The present study was performed to investigate the drug-drug interaction between WF and TEIC in comparison with controls treated with vancomycin (VCM), which has the same spectrum of activity as TEIC but a lower albumin binding ratio.The records of 49 patients treated with WF and TEIC or VCM at Fukuoka University Hospital between 2010 and 2015 were retrospectively reviewed. These 49 patients consisted of 18 treated with TEIC in combination with WF, while 31 received VCM in combination with WF. Prothrombin time-international normalized ratio (PT-INR) showed a significant increase of 80.9 (52.0-155.3) % after co-administration of TEIC with WF. In contrast, the rate of PT-INR elevation associated with VCM plus WF was 30.6 (4.5-44.1) %. These observations suggested that TEIC can cause a rise in free WF concentration by albumin binding interaction. Therefore, careful monitoring of PT-INR elevation is necessary in patients receiving WF plus TEIC.

Influence of genetic polymorphisms in cytochrome P450 oxidoreductase on the variability in stable warfarin maintenance dose in Han Chinese

PURPOSE

The aim of this study was to investigate whether any of the single-nucleotide polymorphisms (SNPs) in the POR gene were significantly associated with CYP activity and expression, and could contribute to the total variability in stable warfarin maintenance doses in Han Chinese.

METHODS

A total of 408 patients treated at the First Affiliated Hospital of Sun Yat-Sen University were eligible for the study and had attained a stable warfarin maintenance dose at the start of the investigation. Demographics, warfarin maintenance doses, and concomitant medications were documented. Genomic DNA was extracted from peripheral blood samples and genotyped for ten SNPs (CYP 2C9*2 and *3, CYP4F2 rs2108622, VKORC1 -1639C>T, and potential POR genes of rs10239977, rs3815455, rs41301394, rs56256515, rs1057868, and rs2286823) using the Sequenom MassARRAY genotyping system.

RESULTS

A predictive model of warfarin maintenance dose was established and indicated that age, gender, body surface area, aspirin use, CYP2C9*3, CYP4F2 rs2108622, VKORC1 -1639C>T, and POR*37 831-35C>T accounted for 42.4 % of dose variance in patients undergoing anticoagulant treatment. The contribution of POR*37 831-35C>T to warfarin dose variation was only 3.9 %.

CONCLUSIONS

For the first time, the SNP POR*37 831-35C>T was confirmed as a minor but statistically significant factor associated with interindividual variation in warfarin maintenance dose in Han Chinese. The POR*37 gene polymorphism should be considered in future algorithms for faster and more reliable achievement of stable warfarin maintenance doses.