Antithrombotic Therapy: Definition & Side Effects

Instructor: Artem Cheprasov
Blood thinners and clot busters. You've probably heard of them, but do you know the names of specific ones and what classes of medication they actually belong to or what side effects they cause? This lesson will tell you!

What is Antithrombotic Therapy?

Have you ever heard of a blood clot? A blood clot is the easy way to say thrombus, singular for thrombi. Thrombi are blood clots that are located within the cardiovascular system. The cardiovascular system consists of your heart and blood vessels and is responsible for circulating blood throughout the body. Blood clots, or thrombi, can cause serious health conditions depending on where they form. They can form in any vessel, including the heart or brain causing heart attack or stroke. Thrombi are also dangerous if they form in one area and then break off and move to another. The type of thrombus that breaks off and moves is called an embolus. When thrombi form, they are like a plug in a pipe. Nothing can get past them. That is why I like to call them blood vessel plugs.

What needs to get past thrombi? Arterial blood, which is blood filled with life giving oxygen. If arterial blood cannot get past the thrombus, what do you think happens to the cells and tissues nourished by that blood vessel? Well, like grass watered by underground pipes dies if those pipes are clogged, cells and tissues not nourished by arterial blood will also die.

This is why antithrombotic therapy, therapy aimed at acting against (anti-) the thrombi, is so important in preventing problems like heart attack and stroke.

Drugs Used in Antithrombotic Therapy

There are three main classes of antithrombotic drugs. These classes are anticoagulants, antiplatelet and thrombolytic.

Anticoagulants are drugs that help prevent clot formation by preventing fibrin formation. Fibrin is a type of protein involved in blood clot formation. Examples of anticoagulants include heparin and warfarin which is known by the brand name Coumadin.

The second type of antithrombotic drug class is the antiplatelet class which help prevent clot formation by stopping components of blood called platelets from clumping together and sticking to passing cells forming plugs. Examples of drugs with antiplatelet properties include aspirin and clopidogrel which is also known as Plavix.

Platelets, the smaller components, clumping together with red blood cells during clot formation
Thrombus

To help you understand all of this for our lesson, you can think of the fibrin as a meshwork of strands that traps platelets and passing blood cells within its network and holds them together. Together, the fibrin, clumped up platelets and trapped cells are what form the clot. Anticoagulants and antiplatelets work to stop clot formation by either preventing fibrin formation, so the meshwork isn't there, or by stopping the platelets from clumping together so they cannot form the plug.

Together, anticoagulants and antiplatelet drugs are known commonly as blood thinners. However, it is important to know that these drugs don't actually thin the blood, they just make it less able to clot.

The third antithrombotic drug class is known as the thrombolytic class, which is a group of drugs that break down (-lytic or -lysis) already formed thrombi. Examples of thrombolytic drugs include tissue plasminogen activator and streptokinase. Thrombolytic drugs are more commonly called clot busters.

Side Effects

The side-effects of these drugs vary from person to person and from drug to drug, but some things to note include the following:

Anticoagulants may have the following side-effects:

  • Fever
  • Nosebleeds, especially those that last longer than 10 minutes
  • Bleeding gums
  • Coughing up blood
  • Cramping
  • Nausea or vomiting (with or without blood)
  • Blood in the urine
  • Diarrhea
  • Blood in the stool. The stool may either have bright red blood or they may be very black as a result of digested blood.
  • Skin rashes
  • Severe bruising
  • Weight loss

Antiplatelet medication may cause:

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