Ecarin Clotting Time

Ecarin = highly puridied metalloprotease isolated from the venom otEchis carinatus.

Generation of meizothrombin (Ecarin + prothrombin), insensitive to heparin. Able to transform fibrinogen into fibrin.

Ecarin Chromogenic Assay --> meizothrombin is measured using a specific chromogenic substrate.

Douxfils J, Muller F et al, Thomb Haemost 2012 May 2;107(5):985-97

Atlernative

Limitations of aPTT

No reflect of circulating concentrations of dabigatran

No demonstrated link with the bleeding risk

Influence of the reagents and instruments : we need more specific recommendations. More studies are needed.

Prolonged aPTT indicates a supratherapeutic concentration but should be interpreted with caution because of the anticoagulant effect could be underestimated.

A normal aPTT exclude probably an anticoagulant effect from dabigatran

Calibrations and controls are essential

Douxfils J, Muller F et al, Thomb Haemost 2012 May 2;107(5):985-97

Protocol

Results in the therapeutic range

«Result in the therapeutic range, defined on in vitro data»

Infratherapeutic results

«Result under the therapeutic range, defined on in vitro data. It is important to check drug interactions and compliance».

Supratherapeutic results

«Result above the therapeutic range, define on in vitro data. It is imporant to check drug interactions and renal/liver functions.

Dose individualisation

According to european guidelines

Rivaroxaban (Xarelto®)

In practice... Rivaroxaban

PT for the monitoring of Rivaroxaban as a screening test.

Chromogenic anti-Xa tests (i.e. Biophen DiXaI or Liquid Anti-Xa)

Rivaroxaban + FXaexcess --> Riva-FXa + FXaresidual

FXaresidual + chromogenic molecule --> 405 nm

Result in ng/mL of rivaroxaban

Limitations of PT

No reflect of the rivaroxaban’s circulating concentration

No demonstrated link with the bleeding risk

Reagents and instruments influence : more studies need to be done to suggest more specific recommendations

INR is not valid !

A normal PT (with sensitive reageant) excludes a significative anticoagulant effect from rivaroxaban

Calibrations and controls are essentials

Protocol

Results in the therapeutic range

«Result in the therapeutic range, defined on in vitro data»

Infratherapeutic results

«Result under the therapeutic range, defined on in vitro data. It is important to check drug interactions and compliance».

Supratherapeutic results

«Result above the therapeutic range, define on in vitro data. It is imporant to check drug interactions and renal/liver functions.

Clinical cases

N° 1 (23/01/1951), (M)

AF

Prostate cancer

COPD III

Pancreatitis 2007

Pulmonary embolism 2009

Peptic ulcer

Atheromatosis

Thrombophilia : FVIII ++ and heterozygous for prothrombin mutation

Renal fuction : Creat. 1,19 mg/dL, CG 59 mL/minLiver function : OK (GGT 115 UI/L (15-73))

N° 1, monitoring Xarelto 15 mg/d

27/07/2012

0 min : 71,03 ng/mL --> therapeutical trough

120 min : 399,13 ng/mL --> supra-therapeutic

180 min : 449,84 ng/mL --> supra-therapeutic

For 20 mg/d

5 32 155 177 290 409Ctrough Cmax

Douxfils J et al, Thromb. Res. 2012, Sep.21

N° 1 - Traitements

Xarelto 15 mg

Cordarone

SimvastatineEsomeprazole

Spiriva, InuvairDurogesic

Rivotril drops

Zestril

Duovent

MontelukastMedrol

Oxygenotherapy

CYP450 and P-gp ?

N° 1 - Traitements

Xarelto 15 mg

Cordarone Simvastatine Esomeprazole

Spiriva, InuvairDurogesic

Rivotril drops Zestril

Duovent

MontelukastMedrol

CYP450 and P-gp ?

Substrate CYP3A4Inhibitor

CYP2C9, 3A4, 2D6, P-gp

Substrate CYP3A4Inhibitor P-gp Substrate CYP3A4

Inhibitor CYP2C19

Inhibitor CYP2C8

Substrate CYP3A4 et P-gp

Substrate CYP3A4

Durg interactions

Amiodarone --> Flécaïnide ? (CYP2D6). Taken for AF post-embolia. Paroxystic, re-evaluation ?

Simvastatine : strong substrate of CYP3A4 (competition ?), principal metabolic pathway --> Pravastatine ?

...

In case of overdose, check the drug interactions ! Often, polymedicated patients !

Substrate CYP3A4Inhibitor

CYP2C9, 3A4, 2D6, P-gp

Cytochromes Cytochromes P450P450

- Hemoproteins particularly implicated in Xenobiotics metabolism.- Localisation in the liver, but also in the gastrointestinal tract.

- Substrates- Inducers- Inhibitors

Major durgs interactions’ mechanism

Rejection in the GI tract

P- glycoprotein

SubstratesInducers + Inhibitors-

Rivaroxaban and DabigatranAbsorption

- Ciclosporine, Tacrolimus- Amiodarone- Simvastatine- Clarithromycin- Ketoconazole- Phenytoïn- Ritonavir

- Ciclosporine- Amiodarone- Verapamil- Ketoconazole- Ritonavir- Tamoxifène- Grapefruit juice

- Rifampicine- Phenytoïn- Dexaméthasone- Millepertuis

«Multi-Drug Resistance Pump»

Common drug interactions

Rifampicine

Ketoconazole

Verapamil

Clarithromycin (particularly in patients with renal impairment)

Millepertuis (Hypercium perforatum)

Carbamazepin or phenytoïn

Ciclosporine, Tacrolimus

Before NOACs administration, drug

anamnesis is mandatory !

N°2, 23/07/1957 (F)

1m61, 108 kg (BMI = 42) after diet !

AF

Renal and liver functions : ok

No response to VKA !

acenocoumarol (Sintrom) : to 15 mg/d with INR = 1

warfarine (Marevan): to 5 mg/d with INR = 1

phenprocoumone (Marcoumar)

«Resistance» to clonazepam, hydroxizine and zolpidem

Stroke on AF, supra-ventricular tachycardia, ...

By pass !

N°2, 23/07/1957 (F)

Rivaroxaban 20 mg (no dabigatran because of the extreme weight)

Switch Clexane --> Rivaroxaban

Last Clexane intake : 17 august, 9h00

First dose of Rivaroxaban : 18 august, 10h05

Complete PK J0, J6 and J56 : 0min, 30min, 1h, 1h30, 2h, 3h, 4h et 6h

Genotyping : CYP3A4, CYP2C9, VKORC1, ...

VKA metabolism

AVK

AVK

Cofactor γ-carboxylationAVK

CYP450 and anticoagulants

AcénocoumarolWarfarine

Rivaroxaban

Phenprocoumone

?

Other genes can be involved...

Genotyping ?

CYP2C9

CYP3A4CYP3A5

ABCB1

VKORC1

TaqMan, Luminex, Genechip, MLPA, Sequencing, ....

N°2, 23/07/1957 (F)

No detection of common mutations for CYP2C9 or VKORC1

! We only find what we are looking for ! Sequencing ?

CYP3A4*22 negative (Haufroid et al)

CYP3A5 positive ! (20% population) --> increase in CYP3A activity

Part in VKA resistance ?

African population is more resistant to VKA and CYP3A5 is more expressed... (--> ?)

PPAR-A, POR*28, ..., under investigation

Assay

PT values are not similar for the different plasmatic concentrations

Anti-Xa assays (chromogenics) give similar results

Cmax 2-4h after intake0 min, 30min, 1h, 1h30, 2h, 3h, 4h et 6h

N°3 : N.J, 17/02/1924 (F)

Femoral neck fracture, accidental fall --> 23/10/2012 in Mont-Godinne

Dabigatran 110 mg bd, AF

Last intake : 22/10 at 22h15

Renal function with CG : 34,8 mL/min

Coagulation assays 23/10 :

aPTT = 64,4 sec (26,0-38,0), TT > 120 sec

N°3 : N.J, 17/02/1924 (F)

Recommandations : with Clcreat 30-50 mL/min --> stop for 4 days before surgery (26/10 ?)

monitoring 25/10 morning + switch to Clexane 40 2x/d ?

Monitoring dabigatran 25/10 --> 0 ng/mL (Hemoclot), aPTT 29,9 sec, TT 23,4 sec.

Surgery the 25/10

NOACs and renal impairment

Dabigatran : ~80% renal elimination.

Rivaroxaban : ~50% renal elimination.

Renal impairment ?

Mild : no recommendation

Moderate (ClCr 30-49 ml/min) --> use with caution, clinical surveillance (bleeding, ...).

Severe (ClCr 15-29 ml/min) : caution ! ... Not recommanded in patient with ClCr < 15 mL/min, risk of bleeding.

European medicines agency

ie : Dabigatran

Cas n°3, 30 mai 1972, (M)

Thrombose de la veine saphène droite en 1997 (à 25 ans) --> Fraxiparine.

Bilan thrombophilie (FV Leiden muté, facteur VIII élevé (180%) (et IX)), antécédents de thromboses familiales.

Enormes difficultés à être mis sous AVK... 2002, embolie pulmonaire. Arrêt AVK --> Fraxiparine

Mis sous HBPM pendant quelques années, mais lui est pénible.

Mise sous Pradaxa au Luxembourg (mutuelle luxembourgeoise), mi-2011.

23/02/2012 : depuis 48h, cordon induré sensible au niveau de la face interne de la jambe droite, notion de voyage en avion en Italie --> thrombophlébite de la veine saphène interne droite. Volumineux caillot visible à l’échographie --> Fraxodi 1 ml 1x/jour.

Pradaxa 110 mg 2co en une prise.

23/02/2012 : Monitoring, délais entre prise et prélèvement : 9h

TCA Synthasil : 47,4 sec (26,0 - 38,0)

TT > 120 sec

Hemoclot Thrombin inhibitor 80 ng/mL. Patient dans la zone thérapeutique*.

Bilan hépatique, rénal --> OK ! Pas de co-médication particulière.

Cas n°3, 30 mai 1972, (M)

* Douxfils J et al, Thrombosis and Haemostasis 107.5/2012

06/04/2012 : sous Pradaxa depuis 1 an, 2x110 mg 1x/jour. Report par le patient de l’oubli d’une dose, et survenue d’un début de phlébite... Après confirmation, passage au Xarelto (a décidé qu’il ne prendrait plus de Pradaxa)

23/10/2012 : oubli de prendre le médicament, survenue douleurs jambes et perturbations de la vue (30 min) --> rentré dans l’ordre à la prise de Xarelto.

Traitement à domicile : Xarelto 20 mg/jourLabo : Rivaroxaban, 20 mg

19/07/2012 : 0 min : 0 ng/mL120 min : 190 ng/mL180 min : 166 ng/mL

23/10/2012 : 0 min : 31 ng/mL120 min : 203 ng/mL180 i 210 / L

Cas n°3, 30 mai 1972, (M)

5 32 155 177 290 409

Cvallée et Cmax dans les intervalles thérapeutiques

Conclusion cas n°3

Manque de compliance ? Le Sintrom n’était pas gérable chez ce patient. «N’en fait qu’à sa tête...»

Fraxiparine OK, mais pénible pour lui.

Monitoring Pradaxa ok, mais pas évident d’évaluer la compliance en faisant du monitoring (non rétrospectif). Aléas dans les prises, épisodes thrombotiques, le patient refuse de continuer à prendre le médicament.

Passage au Xarelto, mieux supporté.

Conclusion

A biological follow-up of NOACs is indicated in some situations

In case of infra- or supra-therapeutic concentration, be careful to renal function, liver function, drug interactions and compliance.

Knowledge for the laboratory of the impact of NOACs on routine coagulation assays !

Physician-Biologist dialogue is of utmost importance !

All this has to be well orchestrated !

Website NTHC (Namur Thrombosis and Hemostasis Center)

Google --> NTHC (first website*)

Practical Guide Rivaroxaban

Practical Guide Dabigatran

*http://www.uclmontgodinne.be/gorganimedical.php?action=servicedetail&serviceid=143

Thanks to...

Ph. J. Douxfils, Pr. JM. Dogné

Ph. AS Larock, Ph G.Remy, Pr. A. Spinewine

Dr V. Mathieux, Pr. F. Mullier, Pr. B. Chatelain, Pr C. Chatelain

Pr. V. Haufroid