Platelet inhibitors sheets | Study notes Science education

Platelet Inhibitors

Platelet inhibitors, also known as antiplatelet

drugs, prevent blood platelets from clumping

together (aggregating) and forming clots.

Clinical Use

Commonly used to prevent thrombosis

(clot formation) in arteries.

Helps reduce risk of:

oHeart attack

oStroke

oPeripheral artery disease

Types of Platelet Inhibitors

1. Aspirin

Mechanism: Irreversibly inhibits COX-1,

reducing thromboxane A2 production.

Uses:

oSecondary prevention of myocardial

infarction

oSecondary prevention of stroke

oIn patients with coronary artery

disease

2. P2Y12 Inhibitors

Examples: Clopidogrel, Prasugrel,

Ticagrelor

Mechanism: Block the P2Y12 ADP

receptor on platelets → reduces platelet

activation and aggregation.

Uses:

oIn combination with aspirin (dual

antiplatelet therapy)

oPatients with acute coronary

syndrome (ACS)

oAfter percutaneous coronary

intervention (PCI)

oFollowing stent placement

3. Glycoprotein IIb/IIIa Inhibitors

Examples: Abciximab, Eptifibatide,

Tirofiban

Mechanism: Block platelet glycoprotein

IIb/IIIa receptors → prevent fibrinogen

binding and platelet aggregation.

Uses:

oGiven intravenously in acute

settings (e.g., during PCI)

oPrevent thrombotic complications

4. Dipyridamole

Mechanism: Inhibits platelet function (exact

pathway involves phosphodiesterase

inhibition and increased adenosine).

Uses:

oOften used in combination with

aspirin for stroke prevention

Generic Name Brand Name(s)

Aspirin Ecotrin, Ascriptin

Clopidogrel Plavix

Dipyridamole Persantine

Dipyridamole +

Aspirin

Aggrenox

Clinical Use

Platelet inhibitors are given as prophylactic

therapy to decrease platelet clumping in patients

with:

Recent stroke

Recent myocardial infarction (MI)

Established peripheral vascular disease

Side Effects

General (Most Common)

Increased risk of bleeding, which may

present as:

oGastrointestinal bleeding

oIntracranial hemorrhage

oEasy bruising

oNosebleeds (epistaxis)

oProlonged bleeding time (e.g., from

cuts)

Drug-Specific Side Effects

Aspirin:

oGastrointestinal irritation and ulcers

oTinnitus (at high doses)

oRare: Chromocytopenic purpura,

isolated thrombotic complications

Ticagrelor:

oDyspnea (shortness of breath)

Thrombolytic Agents

Thrombolytic drugs (also called fibrinolytic agents

or "clot busters") are medications that dissolve

blood clots that have already formed within blood

vessels.

Clinical Use

Primarily used in emergency situations

where rapid restoration of blood flow is

critical, such as:

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Platelet Inhibitors Platelet inhibitors, also known as antiplatelet drugs , prevent blood platelets from clumping together (aggregating) and forming clots. Clinical Use  Commonly used to prevent thrombosis (clot formation) in arteries.  Helps reduce risk of: o Heart attack o Stroke o Peripheral artery disease Types of Platelet Inhibitors

1. Aspirin  Mechanism: Irreversibly inhibits COX-1 , reducing thromboxane A2 production.  Uses: o Secondary prevention of myocardial infarction o Secondary prevention of stroke o In patients with coronary artery **disease

P2Y12 Inhibitors**  Examples: Clopidogrel, Prasugrel, Ticagrelor  Mechanism: Block the P2Y12 ADP receptor on platelets → reduces platelet activation and aggregation.  Uses: o In combination with aspirin ( dual antiplatelet therapy ) o Patients with acute coronary syndrome (ACS) o After percutaneous coronary intervention (PCI) o Following **stent placement
Glycoprotein IIb/IIIa Inhibitors**  Examples: Abciximab, Eptifibatide, Tirofiban  Mechanism: Block platelet glycoprotein IIb/IIIa receptors → prevent fibrinogen binding and platelet aggregation.  Uses: o Given intravenously in acute settings (e.g., during PCI) o Prevent thrombotic complications 4. Dipyridamole  Mechanism: Inhibits platelet function (exact pathway involves phosphodiesterase inhibition and increased adenosine).  Uses: o Often used in combination with aspirin for stroke prevention Generic Name Brand Name(s) Aspirin Ecotrin, Ascriptin Clopidogrel Plavix Dipyridamole Persantine Dipyridamole + Aspirin Aggrenox Clinical Use Platelet inhibitors are given as prophylactic therapy to decrease platelet clumping in patients with:  Recent stroke  Recent myocardial infarction (MI)  Established peripheral vascular disease Side Effects General (Most Common)  Increased risk of bleeding , which may present as: o Gastrointestinal bleeding o Intracranial hemorrhage o Easy bruising o Nosebleeds ( epistaxis ) o Prolonged bleeding time (e.g., from cuts) Drug-Specific Side Effects  Aspirin : o Gastrointestinal irritation and ulcers o Tinnitus (at high doses) o Rare: Chromocytopenic purpura, isolated thrombotic complications  Ticagrelor : o Dyspnea (shortness of breath) Thrombolytic Agents Thrombolytic drugs (also called fibrinolytic agents or "clot busters" ) are medications that dissolve blood clots that have already formed within blood vessels. Clinical Use  Primarily used in emergency situations where rapid restoration of blood flow is critical, such as:

o Acute myocardial infarction (heart attack) o Ischemic stroke o Pulmonary embolism Administration & Clinical Use  Route: Given intravenously (IV)  Timing: Most effective when used within the first few hours (< 6 hours) after: o Acute myocardial infarction (MI) o Cerebrovascular accident (CVA / ischemic stroke)  Effect: Reduces mortality when administered promptly Generic Name Brand Name(s) Alteplase (tPA) Activase Reteplase (r- PA) Retavase Streptokinase Kabikinase Side Effects  Serious side effect: o Bleeding (major risk with all thrombolytics) Types of Thrombolytic Drugs

1. Tissue Plasminogen Activator (tPA)  Mechanism: Directly activates plasminogen to plasmin.  Examples: o Alteplase: Recombinant form of human tPA. o Tenecteplase & Reteplase: Modified versions of tPA with:  Longer half-lives  Different administration protocols 2. Streptokinase  Mechanism: o A bacterial protein that forms a complex with plasminogen → activates it to plasmin.  Note: o Has broader activity but is less specific than tPA. 3. Urokinase  Mechanism: Naturally occurring enzyme that directly converts plasminogen to plasmin.  Use: Less frequently used compared to tPA. Therapeutic Uses of Thrombolytic Agents 1. Acute Myocardial Infarction (Heart Attack)  Used to dissolve clots in coronary arteries.  Restores blood flow to the heart muscle.  Reduces the extent of heart damage. 2. Acute Ischemic Stroke  Breaks down clots in cerebral arteries to restore blood flow to the brain.  Must be administered within a narrow time window : o Typically 3–4.5 hours from symptom onset.  Provides maximum efficacy when given promptly. 3. Pulmonary Embolism  In severe, life-threatening cases , thrombolytics can: o Rapidly dissolve the clot obstructing the pulmonary artery. 4. Deep Vein Thrombosis (DVT)  May be used in severe cases of DVT: o Especially when there is a risk of limb loss o Or other serious complications 5. Peripheral Arterial Thrombosis  Used to dissolve clots in the arteries of the limbs.  Prevents tissue damage and potential amputation. Side Effects and Risks of Thrombolytic Therapy Primary Risk:  Bleeding — due to breakdown of clots and reduced ability of blood to clot. Possible Complications:  Intracranial Hemorrhage o Bleeding within the brain; can be life- threatening.  Gastrointestinal Bleeding o Occurs in the stomach or intestines.  Hematuria o Presence of blood in the urine.  Bleeding at Injection Sites o Especially common when intravenous lines are placed.

o Do not take any other medication without physician approval. o Avoid OTC medications , especially antacids and cold remedies. o Do not abruptly stop taking digitalis after prolonged use → must be tapered gradually under physician supervision.

Monitoring o Regularly check heart rate (HR) and blood pressure (BP).
Consistency o Do not change brand or dosage form being taken — different formulations may act differently.

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