Low-Dose Alteplase to Treat Blood Clots in Deep Leg Veins

2014-08-27 03:54:25 | BioPortfolio


This study will test the effectiveness of low-dose recombinant tissue plasminogen activator (rtPA, or alteplase) in dissolving blood clots in deep leg veins. rtPA is given to patients with heart attacks to dissolve blood clots in blocked coronary arteries. Blood clots that develop in the deep leg veins can cause pain and swelling and may break loose and lodge in the lungs. Current Routine treatments use anticoagulants (blood thinners) such as heparin, or rtPA to dissolve the clots to stop the clots from enlarging. In an earlier study we showed that rtPA could be used to actually dissolve the clots. This study will determine whether lower doses of rtPA can effectively dissolve clots with fewer bleeding complications than the current previous higher-dose regimen.

Patients 18 years of age and older who have blood clots in a deep vein of the pelvis or leg may be eligible for this study if they have had symptoms for 14 days or less and if they have never had clots in their deep veins before.

Participants are admitted to hospital for 3 to 5 days. On the first treatment day, the patient has a venogram to show the location of the clots. The radiologist injects an x-ray contrast material into a small vein in the foot and watches the dye by x-ray as it moves up the leg, revealing the clot(s). A catheter (plastic tube) is then inserted into a vein either behind the knee, in the groin, or in the neck, and advanced until it reaches the clots. When the catheter is in place, rtPA is injected while the radiologist watches the vein under the x-ray image. The amount of rtPa needed will depends on the size of the clot. Up to five venograms may be done if the clot requires the maximum four rtPA treatments allowed in this study. During the treatments, patients receive standard doses of heparin, given continuously by vein, and Coumadin, another blood thinner, taken by mouth. Patients continue taking Coumadin for 6 months.

Blood samples are drawn shortly before the first dose of rtPa and at five time points afterward to measure the rtPa in the circulation and other factors that indicate whether the rtPa is affecting clotting ability. Blood also is drawn at least once a day to monitor heparin levels.

To evaluate the impact of treatment on the function of the leg, patients are evaluated in the Rehabilitation Medicine Department before receiving rtPA and again at the end of the hospitalization. Patients are also fitted for a compression stocking for the leg, which should be worn to reduce the chance of swelling.


Deep venous thrombosis (DVT) of the lower extremities is routinely treated with anticoagulants, which typically yield a satisfactory result, at least in the short term. However, DVT often causes permanent vein damage that leads to late complications. There is evidence that this may be prevented, and therefore long-term sequellae avoided, if the thrombi are dissolved quickly with thrombolytic agents. In a previous protocol we developed a method using intra-clot injections of alteplase (recombinant tissue plasminogen activator, rtPA) for the treatment of lower extremity DVT. Although the treatment was usually successful and complications were uncommon, we think the regimen can be made safer and perhaps even more effective by using a substantially lower dose of alteplase. The current protocol is a pilot study to test this hypothesis. Up to 25 patients with first-time DVT symptomatic for less than or equal to 14 days will be accepted from referring physicians both within and outside the NIH. They will be treated with less than or equal to 10 mg alteplase per day for up to four days. The protocol is designed so that if the low-dose regimen is unsuccessful, the patient will subsequently receive the higher-dose regimen that has previously been shown to be effective. The patients will be anticoagulated for approximately 6 months and re-evaluated after approximately 6 weeks and approximately 6 months with venography and/or duplex sonography.

Study Design

Endpoint Classification: Safety/Efficacy Study, Intervention Model: Single Group Assignment, Masking: Open Label, Primary Purpose: Treatment


Venous Thrombosis


Alteplase (Activase, Genentech)


National Institutes of Health Clinical Center, 9000 Rockville Pike
United States


Active, not recruiting


National Institutes of Health Clinical Center (CC)

Results (where available)

View Results


Published on BioPortfolio: 2014-08-27T03:54:25-0400

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