New insights into treatment of venous thromboembolism

Warfarin dose requirement in patients having severe thrombosis or thrombophilia

AIMS

Warfarin dose requirement varies significantly. We compared the clinically established doses based on international normalized ratio (INR) among patients with severe thrombosis and/or thrombophilia with estimates from genetic dosing algorithms.

METHODS

Fifty patients with severe thrombosis and/or thrombophilia requiring permanent anticoagulation, referred to the Helsinki University Hospital Coagulation Center, were screened for thrombophilias and genotyped for CYP2C9*2 (c.430C>T, rs1799853), CYP2C9*3 (c.1075A>C, rs1057910) and VKORC1 c.-1639G>A (rs9923231) variants. The warfarin maintenance doses (target INR 2.0-3.0 in 94%, 2.5-3.5 in 6%) were estimated by the Gage and the International Warfarin Pharmacogenetics Consortium (IWPC) algorithms. The individual warfarin maintenance dose was tailored, supplementing estimates with comprehensive clinical evaluation and INR data.

RESULTS

Mean patient age was 47 years (range 20-76), and BMI 27 (SD 6), 68% being women. Forty-six (92%) had previous venous or arterial thrombosis, and 26 (52%) had a thrombophilia, with 22% having concurrent aspirin. A total of 40% carried the CYP2C9*2 or *3 allele and 54% carried the VKORC1-1639A allele. The daily mean maintenance dose of warfarin estimated by the Gage algorithm was 5.4 mg (95% CI 4.9-5.9 mg), and by the IWPC algorithm was 5.2 mg (95% CI 4.7-5.7 mg). The daily warfarin maintenance dose after clinical visits and follow-up was higher than the estimates, mean 6.9 mg (95% CI 5.6-8.2 mg, P < 0.006), with highest dose in patients having multiple thrombophilic factors (P < 0.03).

CONCLUSIONS

In severe thrombosis and/or thrombophilia, variation in thrombin generation and pharmacodynamics influences warfarin response. Pharmacogenetic dosing algorithms seem to underestimate dose requirement.

Management considerations for patients with uterine fibroids and concurrent venous thromboembolism

PURPOSE OF REVIEW

The purpose is to provide an update on management strategies for uterine fibroids in the setting of venous thromboembolism (VTE).

RECENT FINDINGS

Uterine fibroids and VTE are independently associated with morbidity and increasing healthcare costs. Women with large uterine fibroids have a higher likelihood of VTE. Current strategies for stratifying patients with VTE take into account the nature of the VTE (i.e., truly provoked or unprovoked) and many patients may only require short-term anticoagulation. In those patients with risk factors for recurrent VTE, longer term anticoagulation may be required.

SUMMARY

In women with large uterine fibroids, the likelihood of concurrent VTE increases. Peri and postoperative management should be determined based on patient-specific risk stratification, with the majority of patients requiring short-term anticoagulation. Further risk stratification may be required for patients with essentially an unprovoked VTE, and consultation with a thrombosis specialist is recommended.

Intracranial bleedings in patients on long-term anticoagulant treatment: Benefits from oral thrombin and factor Xa inhibitors in clinical practice

Dabigatran, a direct thrombin inhibitor and activated factor X inhibitors, rivaroxaban and apixaban, used in the prevention of stroke or systemic embolism in patients with nonvalvular atrial fibrillation (AF), have several advantages over vitamin K antagonists (VKAs). The non-vitamin K oral anticoagulants (NOACs) have been shown to reduce the risk of intracranial bleedings by 50%. The current review summarizes the available data on the epidemiology, mechanisms and treatment of intracranial bleedings observed on oral anticoagulation with the focus on the specificity of NOACs in this context.