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Emerging data in VTE Prevention for Acutely Ill Medical Patients

Edith A. Nutescu, Pharm.D.
September 2004

The recently published PREVENT study (Prospective Evaluation of Dalteparin efficacy for Prevention of venous thrombosis (VTE) in Immobilized Patients Trial) examined the efficacy and safety of dalteparin (a low-molecular-weight heparin) in the prevention of clinically important venous thromboembolic events in medical patients. A total of 3706 patients were randomized to receive either dalteparin (5000IU SC QD) or placebo for 14 days and followed for 90 days. The primary end point was venous thromboembolism detected by compression ultrasound at day 21 and sudden death by day 21. The incidence of venous thromboembolism was significantly lower in the dalteparin group as compared to the placebo group. (2.77% versus 4.96% respectively; p = 0.0015; 45%RRR and 2.19 ARR) This observed benefit in favor of dalteparin was maintained at 90 days. Major bleeding was slightly higher in the dalteparin group versus placebo but not statistically significant. (0.49% versus 0.19% respectively; p = 0.15)

The PREVENT study provides additional information to the existing body of evidence, supporting the use of low-molecular-weight heparin (LMWH) for VTE prevention in medical patients. Two previous studies have compared enoxaparin (a LMWH) and fondaparinux (a synthetic factor-Xa inhibitor) to placebo.1,3 (See Table) These prior studies have demonstrated a reduction in asymptomatic VTE , driven largely by distal deep vein thrombosis (DVT) detected by venography. As the clinical relevance of distal asymptomatic DVT is controversial and symptomatic DVT or asymptomatic proximal DVT are accepted as clinically relevant, the PREVENT study differs from the MEDENOX and ARTEMIS studies in that compression ultrasound was used to assess efficacy. Compared to MEDENOX, patients enrolled in PREVENT were at lower risk of VTE, therefore further extending the appropriateness and applicability of thromboprophylaxis in a broader patient population than previously documented.

Major Placebo Controlled Studies for VTE Prevention in Medical Patients

  MEDENOX (1) PREVENT (2) ARTEMIS (3)
Study Population - Age ≥ 40 yrs, expected hospital stay ≥ 6 days

and
- CHF (NYHA III/IV)
- acute respiratory illness
- infection or bone/joint or inflamed bowel

plus 1 risk factor
- Age ≥ 40 yrs, expected hospital stay ≥ 6 days

and
- CHF (NYHA III/IV)
- acute respiratory failure
- acute severe systemic disease

plus 1 risk factor
- Age ≥ 60 yrs, expected hospital stay ≥ 4 days

and
- CHF (NYHA III/IV)
- acute or chronic lung disease
- acute infectious or inflammatory disease

no other risk factor required
Primary Efficacy Endpoint Efficacy
- distal & proximal venographic DVT
+ symptomatic VTE
+ fatal PE
Efficacy
- ultrasonographic proximal DVT
+ symptomatic VTE
+ fatal PE
Efficacy
- distal & proximal venographic DVT
+ symptomatic VTE
+ fatal PE
Proximal DVT + Symptomatic VTE at D14-21 Enoxaparin: 2.1%
Placebo: 6.6%
P = 0.037
Dalteparin: 2.7%
Placebo: 5.0%
P = 0.002
Fondaparinux: 1.5%
Placebo: 3.4%
P = 0.085
Major Bleeding Enoxaparin: 1.7%
Placebo: 1.1%
ns
Dalteparin: 0.5%
Placebo: 0.2%
ns
Fondaparinux: 0.2%
Placebo: 0.2%
ns

References

1. Samama MM, Cohen AT, Darmon JY, et.al. A comparison of enoxaparin with placebo for the prevention of venous thromboembolism in acutely ill medical patients. N Engl J Med 1999;341:793-800.

2. Leizorovicz A, Cohen AT, Turpie AG, et.al. Randomized, Placebo-Controlled Trial of Dalteparin for the Prevention of Venous Thromboembolism in Acutelly Ill Medical Patients. Circulation 2004;110:874-879.

3. Cohen AT, Davidson BL, Gallus AS, et.al. Fondaparinux for the prevention of VTE in acutely ill medical patients. Blood 2003;102:42. [abstract].

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