Thrombolytic drugs are life-saving medicines used to dissolve already-formed blood clots. They are especially important in acute myocardial infarction, ischemic stroke, and pulmonary embolism.
Among them, alteplase (t-PA) and streptokinase are the most commonly discussed and tested drugs.
What Are Thrombolytic (Fibrinolytic) Drugs?
Thrombolytics are drugs that:
- Activate plasminogen
- Convert it into plasmin
- Plasmin breaks down fibrin clots
Key Point
Thrombolytics dissolve clots that have already formed
(Unlike anticoagulants, which prevent new clots)
The Fibrinolytic System (Quick Review)
| Step | Process |
|---|---|
| 1 | Plasminogen present inside clot |
| 2 | Thrombolytic drug activates plasminogen |
| 3 | Plasmin formed |
| 4 | Fibrin clot degraded |
| 5 | Vessel recanalization |
Alteplase (t-PA)
Basic Introduction
- Alteplase is a recombinant tissue plasminogen activator (rt-PA)
- It is fibrin-specific
- Acts mainly at the site of the clot
Common Brand Names
- Activase
- Cathflo Activase
Mechanism of Action of Alteplase
Step-by-Step
1. Alteplase binds to fibrin within the clotExam Line
Alteplase is fibrin-specific and causes localized clot breakdown
Clinical Uses of Alteplase
1. Acute Ischemic Stroke
- Most important indication
- Given within 3–4.5 hours of symptom onset
2. Acute Myocardial Infarction (STEMI)
When PCI is not immediately available3. Pulmonary Embolism
Massive or high-risk PE4. Catheter Occlusion
Clears blocked central venous cathetersAdvantages of Alteplase
- High fibrin specificity
- Less systemic bleeding than streptokinase
- No antigenicity (recombinant human protein)
- Can be repeated if needed
Streptokinase
Basic Introduction
- Streptokinase is derived from β-hemolytic streptococci
- It is not fibrin-specific
- Acts systemically
Common Brand Names
- Streptase
- Kabikinase
Mechanism of Action of Streptokinase
Step-by-Step
1. Streptokinase forms a complex with plasminogenExam Line
Streptokinase causes non-selective systemic fibrinolysis
Clinical Uses of Streptokinase
1. Acute Myocardial Infarction
Especially in low-resource settings2. Pulmonary Embolism
When alteplase is unavailable3. Deep Vein Thrombosis
Selected severe casesMajor Disadvantage of Streptokinase
❌ Highly antigenic
1. Antibodies may already be present
2. Can cause:
- Allergic reactions
- Fever
- Hypotension
Alteplase vs Streptokinase (High-Yield Comparison)
| Feature | Alteplase | Streptokinase |
|---|---|---|
| Source | Recombinant human t-PA | Bacterial protein |
| Fibrin specificity | High | None |
| Antigenicity | No | Yes |
| Systemic bleeding | Less | More |
| Reuse | Possible | Not recommended |
| Cost | Expensive | Cheap |
Adverse Effects (Very Important)
Common to Both
- Bleeding
- Intracranial hemorrhage (most serious)
Alteplase-Specific
- Lower bleeding risk
- Angioedema (rare)
Streptokinase-Specific
- Fever
- Hypotension
- Allergic reactions
- Anaphylaxis (rare)
Contraindications of Thrombolytic Therapy
Absolute contraindications:
- Active internal bleeding
- Previous hemorrhagic stroke
- Recent major surgery or trauma
- Uncontrolled hypertension
Relative contraindications:
- Pregnancy
- Peptic ulcer disease
- Recent CPR
Thrombolytics vs Anticoagulants vs Antiplatelets
| Drug Type | Main Action |
|---|---|
| Thrombolytics | Dissolve existing clots |
| Anticoagulants | Prevent clot extension |
| Antiplatelets | Prevent platelet aggregation |
Exam-Oriented Memory Tricks
Fibrin Specificity
“Alte = At the clot”
Antigenicity
“Strep → Streptococcal → Antibodies”
FAQs
1. What is alteplase used for?
Alteplase is used in acute ischemic stroke, STEMI, pulmonary embolism, and catheter occlusion.
2. Why is alteplase preferred in stroke?
Because it is fibrin-specific and causes less systemic bleeding.
3. Why is streptokinase antigenic?
It is derived from streptococcal bacteria, leading to antibody formation.
4. Can streptokinase be reused?
No, it should not be reused within 6–12 months due to antibody formation.
5. Which drug has more bleeding risk?
Streptokinase has a higher risk of systemic bleeding.
6. Is alteplase safe in pregnancy?
Generally avoided unless benefits outweigh risks.
7. What is the most dangerous complication of thrombolytics?
Intracranial hemorrhage.
8. Do thrombolytics prevent clot formation?
No, they dissolve already-formed clots.
9. Can thrombolytics be given orally?
No, they are administered intravenously.
10. Which is cheaper: alteplase or streptokinase?
Streptokinase is much cheaper.
