Thrombolytics: Uses, common brands, and safety info

Thrombolytics, sometimes referred to as “clot busters”, are medications used as an emergency treatment for strokes and heart attacks. Thrombolytics dissolve blood clots in order to restore blood flow and prevent damage to the heart and other organs. The process of dissolving, or breaking down, blood clots is known as thrombolysis. For the best outcome, thrombolytics should be given within 30 minutes of the onset of stroke or heart attack symptoms. 

Other thrombolytics

• Streptase (streptokinase)

• Retavase (reteplase)

• Kinlytic (urokinase)

• Abbokinase (urokinase)

What are thrombolytics?

Thrombolytics are drugs used to dissolve blood clots, which may be causing a vascular blockage, or blockage in the blood vessels. This blockage can lead to ischemia, or a reduced supply of blood and oxygen to vital organs like the heart and brain. 

For example, the coronary arteries are vital blood vessels that supply blood and oxygen to the heart. If the coronary arteries are blocked by a blood clot, the heart muscle tissue will not receive enough oxygen and die. Thrombolytic medications can dissolve a blood clot through thrombolysis and restore blood flow to the affected region. Time is of the essence when using thrombolytic agents, and they should be administered within 30 minutes of experiencing symptoms of a stroke or heart attack. 

Thrombolytic therapy, also known as fibrinolytic therapy, is usually administered in emergency room settings as an intravenous (IV) bolus injection. 

How do thrombolytics work?

Thrombolytics therapy works by dissolving blood clots, also known as thrombi. This process of dissolving clots is known as thrombolysis, although it may also be referred to as lysis or fibrinolysis. Blood clots can develop in blood vessels throughout the body, but when clots form in the heart (coronary), brain (cerebral), or lung (pulmonary) vessels, it can be dangerous. Clots in these areas can lead to cardiovascular events, such as heart attacks and strokes. 

Thrombolytic agents are proteases that break down clots formed through the body’s normal clotting cascade. Thrombolytics primarily work by activating a substance known as plasminogen. Plasminogen is then converted to plasmin, an enzyme that breaks down strands of a protein called fibrin. Fibrin is a protein that is formed from fibrinogen and works to hold clots together. Without the cross-links between fibrin molecules, the blood clot loses stability and falls apart. This results in a return of blood flow, or reperfusion, to the affected area.

The longer a blood clot remains intact, the harder it becomes to dissolve. The American Heart Association recommends that thrombolytics be given quickly because fibrin strands can stabilize a blood clot over time. However, therapy may still be successful when given within two hours of heart attack symptoms. If given after this window of time, the chances of reperfusion are much lower, and higher doses of thrombolytic therapy may be needed. After successful thrombolytic therapy, anticoagulation therapy may be given to prevent blood clots from forming again. 

What are thrombolytics used for?

Thrombolytics are primarily used to treat heart attacks and acute ischemic strokes. Thrombolytics may be prescribed for conditions such as:

• Heart attack

• Stroke 

• Deep vein thrombosis (DVT)

• Pulmonary embolism (PE)

• Arterial thrombosis

• IV catheter clots

• Blocked surgical bypass

Types of thrombolytics

The three major classes of thrombolytic agents include tissue plasminogen activator, streptokinase, and urokinase fibrinolytic drugs. Each type dissolves blood clots in a slightly different way.

Tissue plasminogen activator (tPA)

Tissue plasminogen activators are used to treat heart attacks (acute myocardial infarction), acute ischemic stroke caused by blood clots, and pulmonary embolism. They are typically produced using recombinant biotechnology and are often called recombinant tissue plasminogen activators (rtPAs). Drugs that are part of the tPA family include Activase (alteplase), Retavase (reteplase), and TNK-tPA (tenecteplase). Retavase is given to treat a heart attack or pulmonary thromboembolism. 

TNK-tPA is only approved for use during a heart attack. Tissue plasminogen activators are preferred over streptokinase and urokinase agents because they have a higher fibrin specificity and a lower risk of bleeding. 

Streptokinase (SK)

SK thrombolytics are used to treat heart attacks, venous and arterial thrombosis (blood clots in veins or arteries), and pulmonary embolism. These medications are created from purified streptococci bacteria. SK thrombolytics are antigenic, which means they can trigger an allergic reaction in some people. 

SK thrombolytics are less fibrin-specific than tPA and may interfere with clotting mechanisms in the body, which could increase the risk of bleeding. Clinical studies have also shown that streptokinase can activate platelets, which can form a thrombus, or blood clot, and reduce the drug’s effectiveness. Streptase is an SK thrombolytic.

Urokinase (UK)

UK thrombolytics may be referred to as a urinary-type plasminogen activator because it is formed by the kidneys and can be found in the urine. Like SK thrombolytics, it can interfere with clotting throughout the body and can increase the risk of bleeding; however, it has the advantage of not being antigenic. UK thrombolytics are used to treat pulmonary embolism. Abbokinase is a UK thrombolytic.

Who can take thrombolytics?

Adults

Thrombolytics are typically given to adults presenting to the emergency department with a heart attack or acute ischemic stroke. Because thrombolytics are administered as an IV drug, they are almost always administered in a hospital or clinic. 

Time is of the essence when treating conditions with a thrombolytic. The sooner the medicine is given, the more likely it is to be effective. Ideally, a thrombolytic would be administered within 30 minutes of symptom onset, but sometimes delayed treatment is unavoidable. A thrombolytic may still be given up to 12 hours after the onset of a heart attack, up to 6 hours after the start of a stroke, and up to 24 hours after the onset of a pulmonary embolism. 

It is important to determine the type of stroke being experienced before administering thrombolytic therapy. Thrombolytic drugs are only used for embolic strokes, or strokes caused by blood clots. Hemorrhagic strokes are caused by a ruptured blood vessel that causes bleeding in the brain, and a thrombolytic drug could worsen symptoms. A CT perfusion scan is typically used to determine if stroke symptoms are caused by bleeding or a clot before a decision to use a thrombolytic is made. 

Central venous catheters (CVCs) are long-term IV devices used to administer medications. They may be inserted into patients who require doses of a medicine, such as antibiotic therapy or chemotherapy, over a long period of time. CVCs are also used to draw blood from a patient. Inserting a CVC saves a patient from having frequent needle sticks when a nurse needs to administer medicine or draw blood. 

At times, small clots can form an occlusion, or blockage, in a CVC. Rather than removing and replacing the CVC, thrombolytic medication can be instilled in the catheter to dissolve the clot and restore it to a functional status. Activase (alteplase) is a thrombolytic that is commonly used for this purpose. Low-dose alteplase can be used to help clear any blood clots that may have formed in a CVC. 

Children

In general, thrombolytics are not FDA-approved for use in children; however, in some clinical trials, tPA thrombolytics have been administered to children with favorable clinical outcomes. Thrombolytics may be given to children, including neonates, under special circumstances, but they will require extensive monitoring. Children may also be given Activase (alteplase) to restore the function of CVCs. 

Seniors

Thrombolytics may be given to seniors for the same indications as adults. However, seniors have higher risk factors for bleeding complications when given thrombolytics. Seniors often have additional underlying medical conditions that may prohibit the administration of a thrombolytic or require close monitoring. Those with hypertension or who are currently using anticoagulants, like direct thrombin inhibitors, or antiplatelet medications may need extra monitoring. Seniors with a CVC may receive Activase (alteplase), if needed, to restore the function of the CVC.

Are thrombolytics safe?

Thrombolytics are medications that must be administered in controlled settings with intensive monitoring. They are not without risk, and the benefit of the medicine must be weighed against the risk of not treating the condition. The primary risk associated with thrombolytics is bleeding, which may be life-threatening. 

Recalls

• Activase recall, 2/8/2018

Thrombolytic restrictions

Because thrombolytic medications interfere with clotting mechanisms, the major complication associated with thrombolytics is an increased risk of bleeding. The use of thrombolytics should be avoided or monitored in certain situations. Contraindications include a history of any of the following:

• Recent head injury

• Bleeding problems

• Bleeding ulcers

• Pregnancy

• Recent surgery

• The use of a blood thinner medication, such as warfarin, heparin, or other anticoagulants

• Physical trauma

• Uncontrolled severe high blood pressure

• History of intracranial hemorrhage (brain bleeding)

• Brain cancer

• Brain aneurysm

• Suspected aortic dissection

• Recent internal bleeding

Can you take thrombolytics while pregnant or breastfeeding?

Thrombolytics are generally contraindicated in pregnant women due to the risk of bleeding events and fetal harm. However, women who are pregnant may have a five-times higher risk of developing a deep vein thrombosis than a woman who is not pregnant. Clinicians may recommend a thrombolytic for life-threatening situations. However, the use of thrombolytics should be carefully monitored in pregnant women and only used if the benefits outweigh the risks. 

It is not known if thrombolytics pass into breast milk. The benefits of the medication must be weighed against any possible adverse effects when deciding to use a thrombolytic during breastfeeding. 

Are thrombolytics controlled substances?

No, thrombolytics are not controlled substances.

Common thrombolytics side effects

The most common side effects of thrombolytics include:

• Bleeding, which can present as:

  • Nosebleeds

  • Bleeding gums

• Swelling

• Low blood pressure

• Chest pain

• Changes in heart rhythm

• Fatigue or weakness

Severe but rare side effects of thrombolytics may include:

• Anaphylactic allergic reactions

• Major bleeding

• Bleeding in the brain

This list of side effects is not comprehensive. Speaking with a healthcare professional is the best way to get a complete list of side effects and determine whether taking thrombolytics is suitable for you.

How much do thrombolytics cost?

Thrombolytic medications are administered in a hospital or clinic setting. These can be costly medications, and insurance coverage can vary based on your provider. Using a prescription discount card from SingleCare may help reduce the cost of thrombolytics and other medications administered in a hospital setting. Ask the hospital or clinic where you receive the medication to see if they accept SingleCare discount cards.