Anticoagulants compared with anti-inflammatory drugs or placebo for treating people who have venous blood clots

A blood clot can block a venous blood vessel to cause what is known as a thromboembolism. This most often occurs in a leg (deep vein thrombosis) or in the lungs (pulmonary embolism), which can be fatal. Once formed, a blood clot in a leg can increase in size or can move to the lungs and the recommended treatment is to give drugs that thin the blood (anticoagulants). These include heparins and drugs that inhibit the action of vitamin K (warfarin, phenprocoumon, and acenocoumarol). The possible harms caused by anticoagulants include bleeding in the gut or brain and anticoagulant-induced clotting. The review authors made a thorough search of the medical literature looking for controlled studies on people with blood clots in their veins comparing blood thinning drugs (anticoagulants) with drugs to reduce inflammation (non-steroidal anti-inflammatory drugs) or dummy treatment (placebo). Only two small studies with a total of 113 participants treated over three months were identified, which gave inconclusive results. Since the use of anticoagulants is widely accepted in clinical practice, designing and implementing other similar studies would not be ethical.

Authors' conclusions: 

The limited evidence from RCTs of anticoagulants versus NSAIDs or placebo is inconclusive regarding the efficacy and safety of anticoagulants in VTE treatment. The use of anticoagulants is widely accepted in clinical practice, so a further RCT comparing anticoagulants to placebo could not ethically be carried out.

Read the full abstract...

Venous thromboembolism (VTE) is the term given to any thromboembolic event (blocking of a blood vessel by a blood clot) occurring in the venous system. The current treatment recommended for VTE is anticoagulation (reduction of the blood's ability to clot). The aim of this review is to summarize results from randomized controlled trials (RCTs) for the effectiveness of anticoagulants (heparins, including low molecular weight heparins and vitamin K antagonists) in the treatment of VTE, compared to non-steroidal anti-inflammatory drugs (NSAIDs) or placebo.


To examine the randomized controlled evidence for the effectiveness and safety of anticoagulant treatment compared to NSAIDs or placebo in patients with VTE on the incidence of fatal and non-fatal pulmonary emboli (PE) and the recurrence or extension of deep vein thrombosis (DVT).

Search strategy: 

The Cochrane Peripheral Vascular Diseases (PVD) Group searched their Specialized Register (last searched 14 May 2008) and the Cochrane Central Register of Controlled Trials (CENTRAL) database (last searched Issue 2, 2008). In addition, DKC also searched reference lists and contacted pharmaceutical companies and experts in the field.

Selection criteria: 

All randomized trials of anticoagulants versus NSAIDs or placebo in the initial treatment of VTE (DVT or PE or both).

Data collection and analysis: 

DKC and JM independently assessed trial quality and extracted data. JCP (biostatistician) analyzed the design elements and feasibility of a future randomized controlled trial to determine definitively efficacy and safety of anticoagulants in VTE treatment.

Main results: 

Two RCTs were included. Data were not pooled because of heterogeneity between the studies. The two RCTs were too small to determine any difference in mortality, occurrence of pulmonary emboli, progression or return of DVT between patients treated with anticoagulation and those receiving no anticoagulation.