New Oral Anticoagulant Drugs What monitoring if any is required?

Transcription

1 New Oral Anticoagulant Drugs What monitoring if any is required? Michelle Williamson Supervising Scientist High Throughput Haematology Pathology Queensland PAH Laboratory Overview Background What new oral anticoagulants are on the market? What new oral anticoagulants are on the market? What are the implications: for the medical world? for the laboratory? to PoCT? What are the advantages & disadvantages? What are the advantages & disadvantages? What can we expect in the future? 1

2 Anticoagulation Therapy Used for: the prevention and treatment of thromboembolic disorders such as DVT, PE, AF patients undergoing procedures such as a hip replacement Common anticoagulants UFH, LMWH (Parenteral administration) Warfarin (Oral) Vitamin K Antagonists (VKA) Introduced into clinical practice in the 1950 s Until recently the only available oral anticoagulant were the VKAs Most commonly used VKA is warfarin Limitations: Large dosing difference b/w patients Narrow therapeutic window Dietary & drug interactions Routine monitoring necessary Poor management leads to high adverse events 2

3 AF disease burden in Australia Up to 2% of Australians have AF 1 People with AF are up to seven times more likely to suffer a stroke than the general population 2 Strokes are more likely to be severe or fatal in patients with AF than patients without AF 3 In : 3 An estimated 6,300 Australians suffered a stroke for the first time as a result of AF More than 45,000 hospitalisations occurred in Australia due to AF, more than for stroke or heart failure Medical costs, lost productivity, an costs associated with long-term care for those with a disability due to AF were estimated to cost the Australian economy at least $1.25 billion 1. Sturm JW et al. MJA 2002;176: Fuster V et al. Circulation 2006;114:e The economic costs of atrial fibrillation in Australia. PricewaterhouseCoopers, June Prevalence of Diagnosed AF in Adults Go, AS et al, JAMA, May 9, Vol 285, No. 18 3

4 Warfarin Number of reasons for not prescribing Warfarin to Atrial Fibrillation (AF) patients, include: Risk of fall GI bleeds Non compliance Dementia Patient refusal Hx of alcoholism Limited life expectancy Frailty Elderly Poor general health Gross CP, et al. Clin Ther. 2003;25: The ideal Anticoagulant High efficacy, with wide therapeutic & safe window Oral administration & rapid onset of action Predictable anticoagulant effect for dose; preferably fixed dosing Needs to be taken infrequently Does not need to be monitored, but level can be assessed by laboratory testing Rapid & efficacious reversal Low cost Favaloro WJ & Lippi G, Clin Chem Lab Med 2011;49(5):

5 New Oral Anticoagulants (NOACs) Dabigatran Etexilate (Pradxa ) Boehringer Ingelheim Direct Thrombin Inhibitor (DTI) Directly inhibits both free & clot-bound thrombin Rivaroxaban (Xarelto ) Bayer/Johnson & Johnson Direct Fxa Inhibitor Apixaban (Eliquis ) Bristol-Myers Squibb & Pzifer Direct Fxa Inhibitor (both within & outside the prothrombinase complex) Targets of Anticoagulants Influence of New Anticoagulants on Coagulation Tests. White Paper. Helen Mani, PhD et al

6 Warfarin vs NOACs Ansell J, ASH Education Book, December vol 2010 no. 1: VKA s vs NOACs Riva N & Lip G; Pol Arch Med Wewn

7 TGA Approval Indications for Use Pradaxa & Xarelto approved by TGA in October 2008 for the indication: Short term prevention of venous thrombosis in adult patients who have undergone major orthopaedic surgery of the lower limb (elective total hip or knee replacement) In April 2011 the TGA approved Pradaxa for the prevention of stroke and systemic embolism in patients with non-valvular atrial fibrillation and at least one risk factor for stroke 7

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12 Laboratory testing for NOACS Routine lab testing with PT/INR or aptt is of no benefit in monitoring drug dosing Thrombin Clotting Time (TCT) can be used to exclude the presence of thrombin inhibitors such as Dabigatran Anti-Xa activity can be measured to quantify Rivaroxaban and Apixaban levels Dabigatran is best measured by either a dilute thrombin time (e.g Hemoclot) or an Ecarin clot time which produce a linear dose curve Effect of Dabigatran on Coagulation Assays Van Ryn, J et al, Thrombosis and Haemostasis 2010 Jun,103(6):

13 Effect of Dabigatran on Coagulation Assays Van Ryn, J et al, Thrombosis and Haemostasis 2010 Jun,103(6): Therapeutic Dabigatran (Pradaxa ) 13

14 Effect of Rivaroxaban on Coagulation Assays Harenberg J et al, Expert Rev. Hematol. 5(1), (2012) Therapeutic Rivaroxaban (Xarelto ) 14

15 Impact on Laboratories Shift for coagulation laboratories need to ensure laboratory staff are well educated & can interpret results Affects most routine coagulation tests Varies with test/reagent Varies with sampling time Common coagulation tests not suitable for monitoring Loss of potential income APTT & PT/INR are bread & butter Several years before laboratory testing is sufficiently standardised Do we need to monitor? There will be some situations where clinicians need to asses level of anticoagulation: Before surgery At any hospitalisation Any bleeding/haemorrhage Any thrombotic & embolic event Indication for thrombolytic therapy Known suspicion of deterioration or renal function Dehydration Newly confirmed pregnancy Very elderly Children Adherence to therapy/compliance Suspicion of intoxication Harenberg J et al, Expert Rev. Hematol. 5(1), (2012) 15

16 Point of Care Testing NOACs Potential inaccuracy of POC INR in dabigatran treated patients identified patients identified Case 1 59 y/o woman with AF started on warfarin, after 3 days warfarin discontinued & switched to dabigatran (150mg twice a day) 2 days after warfarin was discontinued. Woman referred to an anticoagulation clinic where her POC INR was 7.2. Lab INR 30 minutes later was 1.7. Several repeat POC INRs were elevated & discordant with lab INRs. Baruch L & Sherman O, The Annals of Pharmacotherapy, 2011 July/August, Volume 45 Point of Care Testing NOACs Case 2 52y/o man had warfarin discontinued 10 days prior to ablation procedure for AF. Patient started on dabigatran after ablation as a bridge to warfarin (unapproved indication, as he was unable to afford enoxaparin). POC INR result 16hrs post dose was 1.6. Treatment was switched to enoxaparin. Both case examples 1 & 2 affected the management of the patient Baruch L & Sherman O, The Annals of Pharmacotherapy, 2011 July/August, Volume 45 16

17 Point of Care Testing - NOACs Case 3 64 y/o woman stopped warfarin & started dabigatran 2 weeks prior to visit at clinic & insisted on having INR via POC despite educational efforts to indicate this was no longer needed. POC INR was 2.2. No signs or symptoms of bleeding with patient instructed to continue taking dabigatran. No lab INR performed. DeRemer C et al, Letter to the Editor, j. amjmed, Vol 124, No 9, September 2011 Point of Care Testing - NOACs Case 4 70 y/o man had POC INR mistakenly administered by nurse unfamiliar with dabigatran. Patient verbally verified that he had stopped taking warfarin 30 days previously. POC INR 8.3, laboratory confirmation result INR 1.5. No signs or symptoms of bleeding, patient was instructed to continue his medication (dabigatran) as prescribed. Follow-up bloods revealed aptt of 63.9 & INR of 1.2. POC INR was 4.5. DeRemer C et al, Letter to the Editor, j. amjmed, Vol 124, No 9, September

18 Dabigatran effect on POC INR Van Ryn J, et al, j. amjmed, 2012 Apr;125(4): Impact on Point of Care Testing Incorrect results being acted on resulting in poor patient management patient management Patients transitioning b/w warfarin & dabigatran inadvertently having a POC INR Need an educational drive to all health professionals involved in POCT? Shift away from POCT Loss of income for POCD companies 18

19 Advantages & Disadvantages NOACs Advantage Fixed Dose No laboratory control Few drug interactions No food interactions? Cost effectiveness decrease in pathology, medical visits Greater benefits to patients particularly rural & remote Disadvantage Lack of effective antidote Lack of experience Lack of standardised methods to control anticoagulant effects Impairment of renal function Cost compared to warfarin Decrease in patient/doctor contact 19