Presentation on theme: "Anticoagulation Update"— Presentation transcript:
1Anticoagulation Update David Lovinger, MDAssistant ProfessorProgram in Hospital MedicineUniversity of ChicagoI have no financial conflicts to disclose
2ObjectivesTo learn about new developments in anticoagulation therapy, monitoring and safety.National Patient Safety Goal 3EPharmacogenetic dosing of warfarinUse of very-low dose vitamin K to stabilize INR in hard to control patientsDuration of anticoagulation for patients with VTE
3IntroductionIn both its use and avoidance, anticoagulation is a risky therapy.Warfarin is a very hard drug to dose properly.There are many opportunities to improve the quality of care.
4Risk of Adverse Events for Anticoagulated Patients Adapted from Hylek EM et. al. An analysis of the lowest effective intensity of prophylactic anticoagulation for patients with nonrheumatic atrial fibrillation. NEJM 1996; 335(8):540-6 and Hylek EM and Singer DE. Risk factors for intracranial hemorrhage in outpatients taking warfarin. Ann Intern Med 1994; 120(11):
5Anticoagulation Clinics JCAHO Patient Safety Goal 3E:Mandate:“Reduce the likelihood of patient harm associated with the use of anticoagulation therapy.” Rationale: Anticoagulation is a high risk treatment, which commonly leads to adverse drug events due to the complexity of dosing these medications, monitoring their effects, and ensuring patient compliance with outpatient therapy. The use of standardized practices that include patient involvement can reduce the risk of adverse drug events associated with the use of heparin (unfractionated), low molecular weight heparin (LMWH), warfarin, and other anticoagulants
6Key Ingredients to NPSG “a defined anticoagulation management program”“approved protocols”Proper monitoring (baseline and follow-up INRs)Education of patients and families aboutDietary restrictionsMonitoring/follow-upDrug interactionsOutpatient and inpatient components*Evaluation and monitoring of the program* Not explicitly part of the NPSG, but UCMC has interpreted it to include an inpatient component.
7TimetableApril 1, 2008: The organization’s leadership has assigned responsibility for oversight and coordination of the development, testing, and implementation of NPSG Requirement 3E.July 1, 2008: An implementation work plan is in place that identifies adequate resources, assigned accountabilities, and a time line for full implementation by January 1, 2009.October 1, 2008: Pilot testing in at least one clinical unit is under way.January 1, 2009: The process is fully implemented across the organization.
8Do Clinics Work?In general, there is an increase in time spent in therapeutic range:Time in therapeutic range – standard: 50-55%Time in therapeutic range – clinic: 60-65%Reduction in time spent in “alert” range (INR > 4.0 or < 1.4).1Even self-testing is better than usual care.2In studies of pharmacist managed AC clinic:39% fewer anticoagulation-related complications.3Pt INR’s were in therapeutic range 20% more often. 3Reduction in hospitalizations.41 Personal communication, University of Utah, Chronic Anticoagulation Clinic.2 Connock M, et al, Health Technol Assess, 2007.3 Witt, et al, Chest, 2005.4 Locke, et al, Pharmacotherapy, 2005.
9Do Clinics Work? Yes, but: The model is important: pharmacists are better studied than RN’s.Standardization and continual evaluation are essential.Centralization is likely NOT essential.Small improvements in INR result in significant clinical outcomes.
10Introduction to Warfarin Pharmacogenetics Background on common genetic variants and how they affect warfarin dosing.VKORC1 – affects vitamin K metabolismCYP2C9 – affects warfarin metabolismHow these apply to clinical decisions.Recent evidence regarding the use of warfarin dosing algorithms.
11Warfarin Pharmacology 2 main components to the action of warfarin in the body:Warfarin inhibits Vitamin K Epoxide Reductase (VKOR) which helps recycle Vit K.Warfarin is metabolized via the cytochrome P450 system, specifically, CYP2C9.CYP2C9---|Hall, 2006
12CYP2C9 Variant Alleles Impact Warfarin Metabolism CYP2C9*2 has 30-50% activity of wt (CYO2C9*1.)CYP2C9*3 has 10% activity of wt.These variants account for 12% of the variation in warfarin dose.Dervieux, 2005
13CYP2C9 Allele Frequencies Vary Between Populations CYP2C9*1 (WT)CYP2C9*2CYP2C9*3Caucasian78 – 84%%5 – 10%Asian97.8%-2.2%African-American93.0%5.6%1.4%CYP2C9*2 reduces the rate of metabolism resulting in lower clearance (30-50% activity of WT).CYP2C9*3 has more significantly reduced rate of metabolism and decreased enzyme efficiency (10% activity of WT).Both result in lower need for warfarin and a lower doseNon-WT patients have an increased risk of supratherapeutic INRs and bleeding (Higashi, et al, JAMA, 2002).
14VKORC1 Variants Have Functional Consequences on Warfarin Dose VKORC1 haplotype alone accounts for 21-25% of the variability in warfarin dose.Hap A/A = 2.7±0.2 mg/dayHap A/B = 4.9±0.2 mg/dayHap B/B = 6.2±0.3 mg/dayMechanism of action in these variants is unclear.Variant VKORC1 haplotypes do not appear to have the same bleeding risk of CYP2C9 variants.Reider, 2005
15Frequencies of VKORC1 Variants Form two distinct groups.Hap A is associated with a lower warfarin maintenance dose.Hap B is associated with a higher warfarin maintenance dose.PopulationHap AHap BEuropean%%African American%%Asian%%Peruvian27%71%Mexican38%57%African23%49%
16Variables Known to Influence Warfarin Dose Marsh (2006)
17Algorithm for Dosing Daily dose of warfarin= exp[( x VKOR3673G>A ) + ( x BSA) – ( x CYP2C9*3) – ( x age) – ( x CYP2C9*2) + ( x target INR) – ( x amiodarone) + ( x smokes) – ( x AA race) + ( x VTE)]Difficult to use in clinical practiceEasier to use in clinical practice:Does it work?
18Randomized Trial of Genotype-Guided Versus Standard Warfarin Dosing in Patients Initiating Oral AnticoagulationAnderson JL, Horne BD, Stevens SM, et al. Circulation, 2007;116:
19ObjectiveTo compare the effect of genotype-guided dosing on INR to standard, nomogram-based dosing.
20Methods 206 inpatients in academic medical center. Inclusions: patients with indication for AC (Goal INR 2-3)Exclusions: rifampin, advanced age, renal or hepatic diseaseBlinding: UnblindedRandomized to PG-dosing or standard care based on 10 mg nomogram.Primary endpoint was percentage of INR’s out of range.Secondary endpoints include time to supratherapeutic INR, time in range, percentage of patients at goal by days 5 and 8, number of dosing changes.
21Risk of Adverse Events for Anticoagulated Patients Adapted from Hylek EM et. al. An analysis of the lowest effective intensity of prophylactic anticoagulation for patients with nonrheumatic atrial fibrillation. NEJM 1996; 335(8):540-6 and Hylek EM and Singer DE. Risk factors for intracranial hemorrhage in outpatients taking warfarin. Ann Intern Med 1994; 120(11):
22ResultsWith the exception of the number of dosing changes, there was no difference between the 2 groups.A non-significant trend towards fewer INR’s and fewer supratherapeutic INR’s, but...Small studyTrends are potentially significantBottom line: not ready for widespread use, but will likely be useful in the future.
23Genetic Determinants of Response to Warfarin During Initial Anticoagulation Schwarz UI, Ritchie MD, Bradford Y, et al. N Engl J Med 2008;358:
24ObjectiveTo compare the effect of genotype-guided dosing on INR and bleeding to standard, nomogram-based dosing.
25Methods 328 inpatients in academic medical center. Inclusions: patients with indication for AC (no specific goal)Exclusions: active malignancy or alcoholismBlinding: UnblindedRandomized to PG-dosing or standard care based on 10 mg nomogram.Primary endpoints were time to first INR in therapeutic range, time to first INR > 4.0 and time INR was supratherapeutic.Secondary endpoints were average warfarin dose and bleeding events.
26ResultsPts with VKORC1 A/A haplotype had a significantly faster time to a therapeutic INR and a faster time to supratherapeutic INR.CYP2C9 genotype had no effect on time to first therapeutic INR, but...Non-wt CYP2C9 genotypes had faster time to first supratherapeutic INR.
27Genetic Testing: Summary VKORC and CYP2C9 variants clearly influence warfarin dose.The effects of genetic variation are seen during initiation of therapy, but the longer term effects are not as clear.Clinical factors have roughly the same influence as genetic factors and standardization of the dosing process is beneficial regardless of the algorithm.The proper role for genetic testing is not well defined and further investigation will be needed.
28Daily Vitamin K Supplementation Improves Anticoagulant Stability Rombouts EK, Rosendaal FR, van der Meer JM. J Thromb Haemost 2007;5:2043-8
29BackgroundFluctuations in INR are associated with low baseline vitamin K intake.Small studies have shown value in stabilizing INRs when very low dose vitamin K is added to the diet.
30Methods 200 patients enrolled in a Dutch anticoagulation clinic: Inclusions: age 18-80, on AC for at least 1 yearExclusions: Renal or hepatic disease, pregnancy, non-compliance.Randomized to 100 mcg vitamin K daily or placebo.Primary endpoint was time in therapeutic range.Secondary endpoints was maximal stability (pts with INRs in therapeutic range for the entire study period.)
31ResultsTime in range was 89.5% for the vit K group and 85.5% for the placebo group 4% difference ( ).43% of the vit K group vs. 24% of the placebo group had maximal stability, RR= 1.8 ( ).
32Optimal Duration of Anticoagulation Therapy Pts who have VTE in the setting of transient risk factors (immobility, surgery, trauma, etc) have a low risk of recurrence after appropriate anticoagulation – 3-6 months.5 yr risk of recurrence after provoked VTE 8-12%Pts who have VTE in the setting of long-term risk factors (hereditary thrombophilia, cancer, lupus anticoagulant, etc) have a high risk of recurrence after appropriate anticoagulation 6-12 months.5 yr risk of recurrence after unprovoked VTE = 25%
33Optimal Duration of Anticoagulation Therapy, cont’d Pts who have unprovoked VTE also have an increased risk of recurrence.Current guidelines for unprovoked VTE are for use of VKA for 6-12 months and to consider indefinite AC.Does everyone with unprovoked VTE need indefinite AC?Can we predict who needs indefinite AC?How to determine length of therapy?
34D-Dimer Testing 608 pts w/unprovoked VTE and at least 3 months AC. 223 w/abnormal D-dimer level 30 days after discontinuation of AC.Half were restarted on AC, half were not.Pts w/elevated D-dimer were more likely to have recurrence if not on AC.Palateti G, Cosmi B, Legnani C, et al. N Engl J Med 2006;355:
35Ultrasonography Cohort study of 313 pts in Italy. 3 months of AC. 80 thrombophilia124 unprovoked109 provoked3 months of AC.Serial U/S at 3, 6, 12, 24 and 36 months.Pts w/residual clot on U/S were at much higher risk of recurrent VTE.Prandoni P, Lensing AWA, Prins MH, et al. Ann Intern Med. 2002;137:
36RecommendationsProvoked VTE: 3-6 months, depending on the severity of the event.Unprovoked VTE: 6-12 months AC, followed by:D-Dimer OR venous dopplerIf negative, can discontinue ACIf positive, continue AC and reassess periodicallyChest, 2004 recommends lifelong AC as a reasonable alternative for unprovoked VTE.Recurrent VTE: lifelong AC.
37Recommendations, cont’d VTE and Thrombophilia:APLA, ATIII or Protein C + S def’cy: lifelong ACFactor V Leiden AND Prothrombin Gene mutation 20210: lifelong AC or treat as unprovoked VTE.Factor V Leiden homozygote: lifelong AC or treat as unprovoked VTE.Factor V Leiden heterozygote OR Prothrombin Gene mutation 20210: treat as unprovoked VTE.
38ConclusionsAnticoagulation clinics are likely to become more common as time goes on.Standardization alone can bring significant improvementsGenetic testing is not ready for prime time.Will likely be used in the near futureEffects likely seen in initiation of therapyLow dose vitamin K can help stabilize hard to control patients.Use D-dimer or venous ultrasonography to identify patients at high-risk for recurrent VTE and consider longer duration of AC therapy.