Drugs Acting on Blood and Blood Forming Organs

Definition

These are the drugs which act on blood or blood-forming organs to correct disorders of blood formation (anemia), prevent or treat clot formation (thrombosis), or dissolve already formed clots.

They are mainly divided into:

1. Hematinic agents – increase hemoglobin or RBC production.

2. Anticoagulants – prevent clot formation.

3. Antiplatelet agents – inhibit platelet aggregation.

4. Thrombolytic drugs (fibrinolytics) – dissolve formed clots.

1. Hematinic Agents

Drugs that promote hemoglobin synthesis or increase RBC production.

Classification

• Iron preparations

  • Oral: Ferrous sulfate, ferrous fumarate, ferrous gluconate

  • Parenteral: Iron sucrose, iron dextran, ferric carboxymaltose

• Folic acid

• Vitamin B12 (Cobalamin)

  • Cyanocobalamin, Hydroxocobalamin

• Erythropoiesis-stimulating agents (ESAs)

  • Erythropoietin, Darbepoetin alfa

Pharmacological actions

• Iron → essential for Hb synthesis, myoglobin, enzymes.

• Folic acid & Vitamin B12 → DNA synthesis, RBC maturation.

• Erythropoietin → stimulates RBC production in bone marrow.

Indications

• Iron deficiency anemia

• Megaloblastic anemia (folic acid, vit B12 deficiency)

• Pernicious anemia (Vit B12 injection)

• Anemia in chronic renal failure (Erythropoietin)

Contraindications

• Hemochromatosis, hemosiderosis (Iron overload)

• Megaloblastic anemia due to other causes (don’t give folate alone if Vit B12 deficient → neurological damage may worsen)

• Polycythemia (contraindicated for erythropoietin)

2. Anticoagulants

Drugs that prevent clot formation or extension by inhibiting coagulation factors.

Classification

• Parenteral anticoagulants

• Heparin (UFH):- Heparin is a naturally occurring anticoagulant (glycosaminoglycan) obtained from animal tissues (e.g., lung or intestinal mucosa of pigs/cattle).

  It is widely used to prevent and treat blood clots.

• Mechanism of Action (MOA)

• Heparin binds to antithrombin III (AT-III).

• This enhances AT-III activity → inactivates clotting factors: mainly thrombin (IIa) and Factor Xa.

• Result → Prevents clot formation and extension, but does not dissolve existing clots.

• Indications

  • Prevention & treatment of venous thromboembolism (VTE, DVT, PE)

  • Atrial fibrillation (stroke prevention)

  • Mechanical heart valves (Warfarin)

  • Myocardial infarction (as adjunct)

  Contraindications

  • Active bleeding, hemophilia

  • Severe liver/kidney disease

  • Uncontrolled hypertension

  • Pregnancy (Warfarin is teratogenic, but heparin is safe)

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  3. Antiplatelet Agents

  Drugs that inhibit platelet aggregation and prevent arterial thrombosis.

  Classification

  • COX inhibitor: Aspirin (low dose)

  • ADP receptor (P2Y12) antagonists: Clopidogrel, Prasugrel, Ticagrelor

  • GPIIb/IIIa receptor blockers: Abciximab, Eptifibatide, Tirofiban

  • Phosphodiesterase inhibitors: Dipyridamole, Cilostazol

  Pharmacological actions

  • Aspirin → irreversibly inhibits COX-1 → ↓ thromboxane A2 → prevents platelet aggregation.

  • Clopidogrel/Ticagrelor → block ADP receptor → inhibit platelet activation.

  • GPIIb/IIIa inhibitors → block fibrinogen binding → prevent platelet cross-linking.

  Indications

  • Myocardial infarction, ischemic stroke (prevention and treatment)

  • Coronary artery disease, post-angioplasty/stent

  • Peripheral arterial disease

  Contraindications

  • Active peptic ulcer/bleeding

  • Hemophilia or bleeding disorders

  • Hypersensitivity (e.g., aspirin allergy, asthma)

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  4. Thrombolytic Drugs (Fibrinolytics)

  Drugs that dissolve pre-formed clots by activating fibrinolysis.

  Classification

  • Natural/older agents: Streptokinase, Urokinase

  • Recombinant tissue plasminogen activators (tPA): Alteplase, Reteplase, Tenecteplase

  Pharmacological actions

  • Convert plasminogen → plasmin → degrades fibrin clot.

  Indications

  • Acute myocardial infarction (within 6–12 hrs)

  • Acute ischemic stroke (within 3–4.5 hrs for Alteplase)

  • Pulmonary embolism with hemodynamic compromise

  • Severe DVT (rare)

  Contraindications

• Active internal bleeding

• Recent major surgery or trauma

• Hemorrhagic stroke or history of intracranial bleed

• Severe uncontrolled hypertension

                Drugs Acting on Blood and Blood-Forming Organs

Class	Examples	Pharmacological Action	Indications	Contraindications
Hematinic Agents	Iron (Ferrous sulfate, Iron sucrose), Folic acid, Vit B12 (Cyanocobalamin, Hydroxocobalamin), Erythropoietin	- Iron → Hb & myoglobin synthesis - Folic acid & Vit B12 → DNA synthesis & RBC maturation - Erythropoietin → ↑ RBC production in bone marrow	- Iron deficiency anemia - Megaloblastic anemia - Pernicious anemia (Vit B12) - Anemia of chronic renal failure (Erythropoietin)	- Iron overload (hemochromatosis, hemosiderosis) - Folate alone in Vit B12 deficiency - Polycythemia (Erythropoietin)
Anticoagulants	Parenteral: Heparin, LMWH (Enoxaparin), Fondaparinux Oral: Warfarin, Acenocoumarol DOACs: Dabigatran (IIa inhibitor), Rivaroxaban, Apixaban (Xa inhibitors)	- Heparin → activates antithrombin III → inhibits thrombin & Xa - Warfarin → blocks Vit K dependent factor synthesis (II, VII, IX, X) - DOACs → directly inhibit thrombin or Xa	- Prevention/treatment of DVT, PE - Stroke prevention in AF - Prosthetic heart valves (Warfarin) - MI (adjunct)	- Active bleeding - Severe liver/kidney disease - Uncontrolled hypertension - Pregnancy (Warfarin is teratogenic, Heparin safe)
Antiplatelet Agents	Aspirin (COX inhibitor), Clopidogrel, Prasugrel, Ticagrelor (P2Y12 blockers), Abciximab, Eptifibatide (GPIIb/IIIa blockers), Dipyridamole	- Aspirin → ↓ TXA2 → ↓ platelet aggregation - Clopidogrel → blocks ADP receptor - GPIIb/IIIa blockers → prevent fibrinogen cross-linking	- MI, ischemic stroke (prevention/treatment) - Post-angioplasty/stent - Peripheral arterial disease	- Active peptic ulcer - Hemophilia/bleeding disorder - Aspirin hypersensitivity/asthma
Thrombolytic Drugs	Streptokinase, Urokinase, Alteplase, Reteplase, Tenecteplase	Convert plasminogen → plasmin → dissolves fibrin clot	- Acute MI (within 6–12 hrs) - Acute ischemic stroke (within 3–4.5 hrs for tPA) - Pulmonary embolism with shock	- Active internal bleeding - Recent major surgery/trauma - Hemorrhagic stroke or past intracranial bleed - Severe uncontrolled hypertension