Blood Clots

Balancing the Bleed: The science and pharmacology of blood coagulation By: Mariah Harrison /Group 2

Step 1: The blood vessel narrows.Chemical signals cause injured vessels to narrow to prevent more blood from leaking out. Step 2: Platelets travel to the site of the injury.Chemical signals tells your spleen to release the platelets into your blood. Step 3: A platelet plug forms.The platelets change shape and become stickier. This allows them to attach to the vessel wall and clump together into a plug. Step 4: The blood clot forms. Fibrin, a long, thin, and sticky protein.It forms a mesh to glue the platelet plug in place, called a fibrin clot. Also holds red blood cells to form a blood clot.

(NHLBI, 2022)

Antiplatelet Agents

Therapeutic Actions:Inhibit platelet adhesion and aggregation by blocking receptors sites on the platelet membrane.Anagrelide – Blocks the production of platelets in the bone marrow. Indications:Reduce risk of recurrent TIAs or strokes; reduce death or nonfatal MI; MI prophylaxis; anti-inflammatory, analgesic, and antipyretic effects. Pharmacokinetics:Well absorbed and bound to plasma proteins. Metabolized in the liver and excreted in the urine. Contraindications:Allergy, pregnancy, and lactation Cautions: Bleeding disorder, recent surgery, closed-head injury. Adverse Effects: Bleeding,headache, dizziness, weakness, and GI distress. Drug-to-Drug Interactions: another drug that affects blood clotting. (Lippincott | ThePoint, 2025)

Prototype Drug: Aspirin

Indications:Reduction of the risk of recurrent transient ischemic attacks (TIAs) or strokes in men wiht a history of TIA due to fibrin or platelet emboli;reduction of death or nonfatal myocardial infraction (MI) in patients with a history of infraction or unstable angina, MI prophylaxis; also used for it anti-inflammatory, analgesic, and antipyretic effects.Actions: Inhibits platelet aggregation by inhibiting platelet synthesis of thromboxane A2. Pharmacokinetics: Adverse Effects:Acute aspirin toxicity with hyperpnea, possibly leading to fever, coma, and cardiovascular collapse, nausea, dyspepsia, heartburn, epigastric, discomfort, gastrointestinal bleeding, occult blood loss, dizziness, tinnitus, difficulty hearing, anaphylactoid reaction.

(Lippincott | ThePoint, 2025)

Similarities & Differences Among Drugs in the Same Class

Aspirin

Other Antiplatelets

• abciximab (ReoPro), eptifibatide (generic), tirofiban (Aggrastat) - All have the same route: IV
• Other antiplatelets target different, more specific pathways. Mechanisms of action are different.
• Clopidogrel -

Onset: Slower Peak: 6 hours Duration: Long, 7-10 days

• Inhibits prostaglandin synthesis, thereby inhibiting platelet aggregation. Inhibits platelet aggregation by inactivating (COX-1).
• Onset: 5-30 min
• Peak: 0.25-2 h
• Duration: 3-6 h

• anagrelide (Agrylin), cilostazol (generic), clopidogrel (Plavix), prasugrel (Effient), ticagrelor (Brilinta), ticlopidine (generic), ticlopidine (generic), & Aspirin have the same route: Oral
• All these durgs are classified as Antiplatelets & their primary goal is the prevention of artial thrombotic events, such as heart attacks and strokes.
• Because their anti-clotting effect, all these medications increase the risk of bleeding.

Similarities & Differences Among Drugs Across Classifications

Other Drugs Across Classification

Aspirin/Antiplatelet

Thrombolytics (Alteplase): act after clot formation to dissolve fibrin.

• Antihemophilic & Hemostatic agents: enhance or preserve clotting - oppsite to aspirin.
• Clinical difference: Aspirin is used for prevention (chronic management), while thrombolytics and hemostatic agents are used for acute intervention.

• Mechanism of Actions: Irreversible COX-1 inhibitor → ↓TXA₂
• Duration: 7–10 days (platelet lifespan)
• Route of Administration: oral

Similarities

• Share involvement in the body's hemostasis (blood clotting) system
• Anticoagulant (Heparin/Warfarin): like aspirin act early in hemostasis (platelet phase)

Antihemophilic Agents

Therapeutic Actions:Replace clotting factors that are either genetically missing or low in a particular type of hemophilia.Indications:Prevent blood loss from injury or surgery and to treat bleeding disorders. Pharmacokinetics:Replace normal clotting factors and are processed as such by the body Contraindications:Allergy, Factor IX in the presence of liver disease, and lactation Cautions: pregnancy Adverse Effects: Involve risks associated with the use of blood products. Headache, flushing, fever, chills, & lethargy.Nausea, vomiting, Stinging, itching, and burning at the site of injection. Drug-to-Drug Interactions:Aspirin & NSAIDs

(Lippincott | ThePoint, 2025)

Prototype: antihemophilic factor

Indications:Treatment of classic hemophilia to provide temporary replacement of clotting factors to correct or prevent bleeding episodes or to allow necessary surgery. Actions: Normal plasma protein that is needed for the transformation of prothrobin to thrombin, the final step in the clotting pathway. Pharmacokinetics: Adverse Effects:Allergic reaction, stinging at injection site, headache, rash, chills, nausea, hepatitis, & AIDS(risks associated with the use of blood products).

(Lippincott | ThePoint, 2025)

Similarities & Differences Among Drugs in the Same Class

OtherAntihemophilic

Antihemophilic Factor

• Mechanism of Action: Replaces the missing Factor VIII, a key cofactor in the intrinsic pathway, enabling the normal coagulation cascade to proceed.

• Mechanism of Action:

Factor IX: Replaces the missing Factor IX, a pro-enzyme in the intrinsic pathway, allowing the normal coagulation cascade to proceed. antiinhibitor coagulant complex: A "bypassing agent" that promotes clot formation by activating the coagulation cascade at multiple sites, bypassing the need for factors VIII or IX. coagulation factor: A "bypassing agent" that binds to tissue factor and directly activates Factor X and Factor IX, initiating the extrinsic pathway to generate thrombin independently of FVIII or FIX.

• Share treating and preventing bleeding in conditions like hemophilia by increasing the body's ability to clot.
• Have the same route: IV injection

(Lippincott | ThePoint, 2025)

Similarities & Differences Among Drugs Across Classifications

(Lippincott | ThePoint, 2025)

Antihemophilic Factor

Other Drugs Across Classifications

• Promote clotting to stop bleeding.
• Treatment of classic hemophilia to provide temporary replacement of clotting factors to correct or prevent bleeding episodes or to allow necessary surgery.
• Onset, Peak, and Duration: Unknown

• All target and interact with the hemostasis system.

• All these drugs modify the body's natural coagulation and fibrinolysis pathways.
• Antihemophilic factors and hemostatic agents work to promote blood clotting (pro-coagulant effect)

• Anticoagulants and thrombolytics work to inhibit or reverse clotting (anti-coagulant/fibrinolytic effect).
• Anticoagulants interfere with the chemical reactions required to produce fibrin (the clot meshwork)
• Thrombolytics are enzymes that break down the established fibrin structure of an existing clot.