Dual antiplatelet therapy (DAPT) is a medical treatment that involves taking two different types of antiplatelet medications simultaneously. The primary goal is to prevent harmful blood clots. These medications work by targeting platelets, the small cell fragments in blood responsible for forming clots to stop bleeding. By making platelets less likely to clump together and form a blockage, DAPT helps maintain blood flow through the vessels.
This therapeutic approach is used for managing specific cardiovascular conditions where the risk of a blood clot is significantly elevated. The decision to use DAPT is made by a healthcare provider based on a careful evaluation of a patient’s specific medical situation.
The Purpose of Dual Antiplatelet Therapy
The most common reason for prescribing DAPT is following a percutaneous coronary intervention (PCI), where a stent is placed in a coronary artery. Stents are small, mesh-like tubes that hold open a narrowed artery, restoring blood flow. However, the body can perceive the stent as a foreign object, triggering a clotting response around it. This can lead to stent thrombosis, where a clot forms inside the stent, abruptly blocking blood flow and causing a heart attack. DAPT is highly effective at preventing this complication.
Another primary use for this therapy is after an acute coronary syndrome (ACS), a term for situations where blood supply to the heart is suddenly blocked, including a heart attack. In these cases, DAPT helps stabilize the plaque that ruptured and lowers the risk of a future heart attack or stroke.
DAPT is also prescribed for patients who have experienced a minor ischemic stroke or a transient ischemic attack (TIA). For these individuals, the combination of medications is more effective than aspirin alone in reducing the risk of a subsequent, more severe stroke.
How Dual Antiplatelet Therapy Works
To understand how DAPT functions, it helps to know the normal role of platelets. When a blood vessel is injured, platelets rush to the site, change shape, and become “sticky,” allowing them to clump together and form an initial plug. This process is called platelet aggregation.
DAPT interferes with this process by using two drugs that target different activation pathways. The first medication is aspirin, which works by blocking an enzyme called cyclooxygenase-1 (COX-1). This enzyme is responsible for producing thromboxane A2, a substance that causes platelets to aggregate. By inhibiting its production, aspirin reduces the stickiness of platelets for their entire lifespan.
The second component of DAPT is a P2Y12 inhibitor. This class of drugs works by blocking the P2Y12 receptor on the surface of platelets. This receptor, when activated by adenosine diphosphate (ADP), sends a strong signal for platelets to clump together. By blocking this receptor, the P2Y12 inhibitor prevents ADP from delivering its message, making it significantly harder for a dangerous clot to form.
Common Medications Used
Dual antiplatelet therapy uses a foundation of aspirin combined with a second antiplatelet agent. The standard dose of aspirin in DAPT is a low dose, such as 75mg or 81mg, taken once daily. For most patients with coronary artery disease, aspirin is recommended for life.
The second medication is a P2Y12 inhibitor, with the most frequently prescribed options being clopidogrel (Plavix), ticagrelor (Brilinta), and prasugrel (Effient). The choice of which P2Y12 inhibitor to use depends on the patient’s specific clinical situation, such as whether they had a heart attack or a stable condition requiring a stent.
A physician also considers a patient’s individual risk for both clotting and bleeding. For instance, prasugrel is not recommended for patients with a history of stroke due to an increased risk of bleeding in the brain.
Duration and Adherence to Therapy
The length of time a person needs to take DAPT is determined by their doctor. The treatment period can range from one month to a year, or in some cases, longer. This decision is based on a balance between the patient’s risk of developing a blood clot versus their risk of bleeding complications. For example, after a routine stent placement for stable coronary artery disease, a shorter duration may be recommended, while after a heart attack, a course of at least 12 months is common.
It is important for patients to adhere strictly to their prescribed DAPT regimen. Stopping either medication prematurely without instruction from a cardiologist can have serious consequences, as it dramatically increases the risk of stent thrombosis. Patients should never stop taking their DAPT unless directed by the healthcare provider who prescribed it.
If a dose is missed, it should be taken as soon as it is remembered. However, if it is close to the time for the next scheduled dose, the missed dose should be skipped to avoid taking a double dose. Consistent communication with the healthcare team is necessary to manage the therapy safely.
Managing Potential Side Effects
The primary side effect associated with DAPT is an increased risk of bleeding. Because the medications interfere with clotting, they can make it harder for the body to stop bleeding when an injury occurs. This can range from minor issues to more serious events.
It is common for people on DAPT to bruise more easily or notice that small cuts take longer than usual to stop bleeding. More significant bleeding requires prompt medical attention. Signs of serious bleeding include seeing blood in the urine or stool (which may appear red, black, or tarry), coughing up blood, or experiencing a severe headache that is different from usual.
Gastrointestinal bleeding is the most common form of major bleeding, and a doctor might prescribe a medication to decrease stomach acid production.
It is important for anyone taking DAPT to inform all of their healthcare providers, including dentists, that they are on this therapy before any planned surgical or dental procedure. This allows for proper planning to manage bleeding risk. Wearing a medical alert bracelet or carrying a card that lists the medications is also a helpful safety measure.