What is the recommended dose of thrombolysis (thrombolytic therapy) for a patient with ST-Elevation Myocardial Infarction (STEMI)?

Thrombolytic Dosing for STEMI

For STEMI patients requiring thrombolysis, use tenecteplase as a single weight-based IV bolus (30-50 mg based on body weight) over 5 seconds, which is the preferred fibrin-specific agent over alteplase or reteplase. 1, 2

Specific Thrombolytic Agent Dosing

Tenecteplase (Preferred Agent)

Weight-based single bolus administration over 5 seconds: 2

• <60 kg: 30 mg (6 mL)
• 60 to <70 kg: 35 mg (7 mL)
• 70 to <80 kg: 40 mg (8 mL)
• 80 to <90 kg: 45 mg (9 mL)
• ≥90 kg: 50 mg (10 mL)

Alteplase (Alternative)

Administered as IV bolus followed by infusion: 1

• 15 mg IV bolus
• 0.75 mg/kg over 30 minutes (maximum 50 mg)
• 0.5 mg/kg over 60 minutes (maximum 35 mg)
• Total maximum dose: 100 mg

Reteplase (Alternative)

Double bolus regimen: 1

• 10 units IV bolus
• Second 10 units IV bolus 30 minutes later

Streptokinase (Least Preferred)

1.5 million units IV over 30-60 minutes 1

• Associated with higher mortality compared to newer agents 3
• Contraindicated if prior streptokinase use within 6 months 1

Timing Requirements

Initiate thrombolysis within 30 minutes of first medical contact when primary PCI cannot be performed within 120 minutes. 1

• Optimal window: <12 hours from symptom onset 1
• May consider: 12-24 hours if ongoing ischemia with large myocardium at risk or hemodynamic instability 1
• Contraindicated: ST depression (unless true posterior MI) 1

Mandatory Adjunctive Antiplatelet Therapy

Aspirin

Loading dose: 162-325 mg orally (chewable/non-enteric coated) or 250-500 mg IV if oral not possible 1

• Maintenance: 81 mg daily indefinitely (preferred over higher doses) 1

Clopidogrel

Age-based loading dose: 1

• ≤75 years: 300 mg loading dose
• >75 years: 75 mg loading dose (no bolus)
• Maintenance: 75 mg daily for minimum 14 days, ideally up to 1 year 1

Mandatory Adjunctive Anticoagulation

Continue anticoagulation for minimum 48 hours, preferably until revascularization or up to 8 days of hospitalization. 1, 4

Enoxaparin (Preferred)

Age and renal-adjusted dosing: 1, 4

• <75 years: 30 mg IV bolus, then 1 mg/kg subcutaneous every 12 hours (maximum 100 mg first 2 doses)
• ≥75 years: No bolus, 0.75 mg/kg subcutaneous every 12 hours (maximum 75 mg first 2 doses)
• CrCl <30 mL/min: 1 mg/kg subcutaneous every 24 hours

Unfractionated Heparin (Alternative)

Weight-adjusted bolus and infusion: 1

• 60 units/kg IV bolus (maximum 4000 units)
• 12 units/kg/hour infusion (maximum 1000 units/hour)
• Target aPTT: 1.5-2.0 times control (50-70 seconds) for 48 hours

Fondaparinux (Third-Line)

2.5 mg IV initial dose, then 2.5 mg subcutaneous daily 1

• Only if CrCl >30 mL/min
• Continue until revascularization or up to 8 days

Critical Post-Thrombolysis Management

All patients must be immediately transferred to a PCI-capable center after thrombolysis. 1, 4

Rescue PCI Indications

Perform immediately if: 1

• <50% ST-segment resolution at 60-90 minutes (failed thrombolysis)
• Hemodynamic instability or cardiogenic shock
• Electrical instability
• Worsening ischemia or evidence of reocclusion

Routine Angiography Timing

Perform angiography and PCI if indicated between 2-24 hours after successful thrombolysis. 1, 4

Key Contraindications

Absolute Contraindications 1

• Any prior intracranial hemorrhage
• Ischemic stroke within 3 months (except acute stroke <4.5 hours)
• Known intracranial vascular malformation or neoplasm
• Active internal bleeding or bleeding diathesis
• Suspected aortic dissection
• Significant closed-head/facial trauma within 3 months
• Severe uncontrolled hypertension unresponsive to emergency therapy

Relative Contraindications 1

• SBP >180 mmHg or DBP >110 mmHg on presentation
• History of ischemic stroke >3 months ago
• Traumatic/prolonged CPR (>10 minutes)
• Major surgery within 3 weeks
• Pregnancy
• Active peptic ulcer

Critical Pitfalls to Avoid

Never use fondaparinux as sole anticoagulant for primary PCI due to catheter thrombosis risk. 1

Flush all dextrose-containing IV lines with normal saline before and after tenecteplase administration to prevent precipitation. 2

Do not administer prasugrel to patients receiving thrombolysis—use clopidogrel instead. 1

Avoid GP IIb/IIIa inhibitors upstream with thrombolysis—reserve for high intracoronary thrombus burden during PCI only. 5