update on the new oral anticoagulants eliot williams, md phd division of hematology & medical...
TRANSCRIPT
Update on the New Oral Anticoagulants
Eliot Williams, MD PhD
Division of Hematology & Medical Oncology
History of anticoagulant therapy
1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 2010
Anticoagulant in spoiled sweet clover (K.P. Link)
First clinical use of 4-hydroxycoumarin (O. Meyer et al)
Warfarin mechanism elucidated (J. Suttie)
Warfarin dosing/INR
Warfarin clinical trials
Oral thrombin and Xa inhibitors
Heparin discovered by medical student (McLean)
Clinical use of heparin
Requirement for plasma cofactor discovered(K. Brinkhous)
Cont infusion of heparin; aPTT monitoring
LMWH (J. Hirsch)
LMWH trials
Fondaparinux trials
New oral anticoagulants• Dabigatran (Pradaxa®) – thrombin inhibitor
– FDA approval 2010: stroke prevention in non-valvular Afib
• Rivaroxaban (Xarelto®) – Xa inhibitor– FDA approval 2010/11: postop VTE prophylaxis,
stroke prevention in Afib, treatment of VTE• Apixaban (Eliquis®) – Xa inhibitor
– FDA approval 2012: stroke prevention in Afib; approved 2014 for VTE prophylaxis after major orthopedic surgery
• Edoxaban – Xa inhibitor– Not yet FDA approved
Pharmacology of oral anticoagulant drugs
Warfarin New agentsBioavailability 99% 6-80% (some active drug
in large bowel)
Tmax 72-96 hours 2-4 hours
Half-life 40 hours 5-17 hours
Metabolism Cytochrome P450 Biliary/Renal
Drug Interactions Many Not so many
Food Interactions Yes No
Genetic Variation Major effects Minor effects (?)
Monitoring PT/INR None
Reversal Vit K/PCC/FFP PCC?Dialysis?
Cost per month of oral anticoagulants
• Rivaroxaban (20 mg/day) : $290
• Dabigatran (150 mg bid): $290
• Apixaban (5 mg bid): $147
• Warfarin (7.5 mg/day): $31
Source: UWHC Pharmacy
Dabigatran• Dose
– Stroke prevention in A fib: 110-150 mg bid• 110 mg dose not available in US• For patients with CrCl 15-30: 75 mg bid• Not recommended for CrCl < 15 or dialysis dependent
– Postop VTE prophylaxis*: 150-220 mg once daily– Prevention of recurrent VTE*: 150 mg bid
• Less than 10% absorbed; relatively high rate of GI side effects• Crosses the placenta – do not use during pregnancy• Drug may degrade over time after exposure to air – must be
kept in original packaging
Unused tablets should be discarded after 90 days
* Not FDA-approved indication
Rivaroxaban• Dose:
– Stroke prevention in Afib: 15-20 mg once daily– Post op VTE prophylaxis: 10 mg once daily– Acute VTE treatment: 15 mg twice daily– Secondary prevention of VTE: 20 mg once daily– Acute coronary syndrome*: 2.5-5 mg twice daily
• Use with caution in moderate renal impairment (CrCL 30-49); 15 mg/day dose recommended– Avoid use if CrCl < 30 (not dialyzable)
• Avoid use in severe liver disease
*Not FDA-approved indication
Apixaban
• Dose: – Stroke prevention in Afib: 5 mg bid
• 2.5 mg bid if age >80, weight < 60 kg, or serum creatinine > 1.5
– Post op VTE prophylaxis*: 2.5 mg bid– Secondary prevention of VTE*: 2.5-5 mg bid– Treatment of acute VTE*: 10 mg bid– Secondary prevention of VTE*: 5 mg bid
• Avoid use in severe liver disease (75% biliary excretion)
*Not FDA-approved indication
NEW ORAL ANTICOAGULANTS VS WARFARIN IN NON-VALVULAR ATRIAL FIBRILLATION
• All randomized; RE-LY unblinded• All designed as non-inferiority trials• Primary outcome was stroke or embolism• All funded by drug manufacturer
Trial Drug being compared
# subjects CHADS2
(mean)TTR
(median)
RE-LY Dabigatran(two doses)
18,113 2.1 67%
ROCKET-AF Rivaroxaban 14,264 3.5 58%
ARISTOTLE Apixaban 18,201 2.1 66%
ENGAGEAF-TIMI 48
Edoxaban(two doses)
21,105 2.8 68%
NEJM 2009; 361: 1139 NEJM 2011; 365:883 NEJM 2011; 365:981
NEW ORAL ANTICOAGULANTS VS WARFARIN: RISK OF STROKE OR EMBOLISM
Dabigatran 150 mg bid
Rivaroxaban 20 mg qd
Apixaban 5 mg bid
Edoxaban 60 mg qd
Combined
Ruff et al, Lancet 2013
NEW ORAL ANTICOAGULANTS VS WARFARIN: RISK OF MAJOR BLEEDING
Ruff et al, Lancet 2013
Dabigatran 150 mg bid
Rivaroxaban 20 mg qd
Apixaban 5 mg bid
Edoxaban 60 mg qd
Combined
Bleeding rates with dabigatran vs warfarin as a function of age
Circulation 2011;123:2363
• Intracranial bleeding lower with dabigatran at all ages• Extracranial bleeding rates higher with dabigatran above age 75
Warfarin
D 110
D 150
Warfarin
D 150D 110
Dabigatran use associated with higher risk of coronary events
←Risk lower with dabigatran Risk higher with dabigatran→
Arch Intern Med 2012;172:397
LESSONS FROM AF TRIALS WITH NEW ORAL AGENTS
• Main result: New agents at least as effective as warfarin, can be given without routine monitoring
• Other/unexpected findings:– Reduction in intracranial bleeding– Higher MI rates (dabigatran)– Higher rates of GI bleeding (active drug in lower
intestine)– Extracranial bleeding risk higher in older patients
Relative efficacy and safety of apixaban vs warfarin, according to adequacy of individual INR control
Wallentin et al, Circulation 2013
Favors apixaban Favors warfarin
The benefit of switching from warfarin to a NOAC appears to be greatest in patients with relatively poor INR control
Can the new oral agents be used in patients with mechanical valves?
• Randomized trial of dabigatran vs warfarin in patients with mechanical valves showed more thrombotic complications (5% vs 0) and more bleeding (4% vs 2%) with dabigatran (Eikelboom et al, NEJM 2013; 369:1206)
DO NOT USE NOACs IN PATIENTS WITH MECHANICAL VALVES
Efficacy of NOACs for treatment of acute VTE is comparable to warfarin
meta-analysis of phase 3 trials
J Thromb Haemost 2014;12:320
Safety of NOACs for treatment of acute VTE is superior to warfarinmeta-analysis of phase 3 trials
J Thromb Haemost 2014;12:320
NOACs for treatment of VTE
• Efficacy comparable to warfarin• Modest safety advantage• Practical advantages
– No monitoring– No injections– No transitioning – single agent treatment– Shorter hospital stay
NOACs vs LMWH after total hip or knee arthroplastyA systematic review of the literature
Ann Intern Med 2013;159:275
Mortality
Symptomatic DVT
Nonfatal PE
Major bleeding
Dabigatran vs LMWH Xa inhibitors vs LMWH
Less thrombosis, more bleeding with NOACs
New oral anticoagulants plus antiplatelet therapy in ACS: meta-analysis
Arch Intern Med 2012; 172:1537
Favors NOA Favors placebo
Non-significant decrease in overall mortality, large increase in risk for major bleeding
Effects of NOACs on routine coag tests
• PT/INR and PTT are relatively insensitive to the effects of these drugs– Reagent-dependent – results will vary among labs
• Normal PT and PTT do not rule out significant blood level of NOAC
• If PT or PTT elevated → assume significant blood levels of NOAC
• Thrombin time very sensitive to dabigatran effect – normal TT implies no drug on board– Rivaroxaban & apixaban do not affect TT
Measuring blood levels of NOACs
• Dabigatran:– Modified thrombin time assay (Hemoclot®)
• Rivaroxaban and apixaban:– Anti-Xa activity (similar to LMWH assay)
• Neither assay FDA-approved or widely available now• When to consider measuring drug level:
– Detect/quantify overdose– Screen for drug accumulation (eg, impaired renal or liver
function)– Assure low drug level prior to surgery
Limited usefulness for assessing compliance due to short drug half-lives
REVERSAL?• No specific antidote for any of the new OACs
– New agents in development may solve this problem• Activated charcoal will reduce drug absorption if
administered within a few hours of ingestion• Rivaroxaban & apixaban effect may be reversed by
giving prothrombin complex concentrate (PCC) (limited data)
• Dabigatran is dialyzable– 60% removed/3 hours, with rebound effect
• Case reports suggest that recombinant factor VIIa (NovoSeven™) is ineffective vs dabigatran (Thromb Haemost 2012;108:585)
Risk-benefit profile of NOACs vs warfarin remains favorable in patients with moderate renal insufficiency (GFR < 50)
Meta-analysis of 9 phase III trials
J Thromb Haemost 2014;12:337
Thrombotic events Major bleeding
% of drug excreted by kidneys →
VKA better
NOAC better
VKA better
NOAC better
Transitioning to NOACs
• Unfractionated heparin to NOAC: – Start NOAC when UFH infusion stopped
• LMWH to NOAC: – Start NOAC 2 h before next scheduled sq dose of
LMWH• Warfarin to NOAC:
– When INR < 2.0
Transitioning from NOACs
• NOAC to parenteral anticoagulant: – CrCl >30: start 12 hours after last NOAC dose– CrCl <30: start 24 hours after last NOAC dose
• NOAC to warfarin:– CrCl >50: start warfarin 3 days before NOAC stopped– CrCl 31-50: start warfarin 2 days before NOAC
stopped– CrCl 15-30: start warfarin 1 day before NOAC stoppedRemember that NOACs can prolong PT/INR
When to stop drug before surgery
• Stop NOAC at least 3 drug half-lives prior to surgery– Dabigatran: 42-51 h– Rivaroxaban: 15-27 h– Apixaban: 24-48 h
• Allow more time if:– Age > 75– Impaired renal or liver function– High bleeding risk
Who are the best candidates for new oral anticoagulants?
• Patients who have unstable INR on warfarin not due to poor compliance
• Reasonably good renal & hepatic function• No mechanical valve • Not pregnant (drugs cross placenta)• < 75 years old• No history of lower GI bleeding• Not at high risk for ACS (dabigatran)