What is the recommended dose, administration method, contraindications, and monitoring for Tenecteplase in adults with acute ST‑segment‑elevation myocardial infarction (STEMI) when timely percutaneous coronary intervention (PCI) cannot be performed within 90 minutes?

Tenecteplase for STEMI When Timely PCI Cannot Be Performed

Tenecteplase should be administered as a single weight-adjusted intravenous bolus when primary PCI cannot be performed within 90-120 minutes of first medical contact in adults with STEMI presenting within 12 hours of symptom onset, provided no absolute contraindications exist. 1, 2

Dosing Regimen

Weight-Adjusted Single Bolus Administration:

• <60 kg: 30 mg 2, 3
• 60-69 kg: 35 mg 2, 3
• 70-79 kg: 40 mg 2, 3
• 80-89 kg: 45 mg 2, 3
• ≥90 kg: 50 mg 2, 3

Critical Age-Related Modification:

• Patients ≥75 years: Reduce dose by 50% to minimize stroke risk 2, 4
• This dose reduction is essential—full-dose tenecteplase in older patients increases intracranial hemorrhage risk to 1.5% even with half-dosing 4

Administration Method

Delivery Protocol:

• Administer as a single intravenous bolus over 5 seconds 3, 5
• Initiate treatment as soon as possible after STEMI diagnosis, ideally within 30 minutes of hospital presentation as a systems goal 1
• Pre-hospital administration is preferred when feasible to minimize total ischemic time 2

Pharmacokinetic Advantage:

• Tenecteplase has a 4-fold slower plasma clearance (105 mL/min) compared to alteplase, with an initial half-life of 22 minutes and terminal half-life of 115 minutes, enabling single-bolus administration 5, 6

Absolute Contraindications

Do Not Administer Tenecteplase If:

• Any prior intracranial hemorrhage at any time 3, 2
• Known structural cerebral vascular lesion (arteriovenous malformation or aneurysm) 3, 2
• Known intracranial neoplasm 3, 2
• Ischemic stroke within 3 months 3, 2
• Suspected aortic dissection 3, 2
• Active internal bleeding 3
• Known bleeding diathesis 3
• Severe uncontrolled hypertension 3, 7
• Intracranial or intraspinal surgery or significant closed-head trauma within 2 months 3

Critical Pitfall: ST-segment depression is a contraindication unless true posterior (inferobasal) MI is suspected or when associated with ST elevation in lead aVR 1

Mandatory Adjunctive Therapy

Antiplatelet Regimen:

• Aspirin: 150-325 mg orally (chewed immediately) or 250 mg IV if oral route impossible, followed by 75-160 mg daily 2, 8
• Clopidogrel: Load with 300 mg, then 75 mg daily 2

Anticoagulation (Choose One):

• Enoxaparin (preferred): IV bolus followed by subcutaneous dosing until revascularization or up to 8 days of hospitalization 2
• Unfractionated heparin: Weight-adjusted IV bolus followed by infusion for 24-48 hours 2, 8

Post-Fibrinolytic Management Strategy

Immediate Transfer Protocol:

• All patients must be transferred to a PCI-capable center immediately after tenecteplase administration without waiting to assess reperfusion success 2, 7
• Target median time from tenecteplase to catheterization: approximately 2.8 hours 2

Timing of Angiography:

• Routine angiography: Perform between 2-24 hours after successful fibrinolysis 2, 7
• This pharmacoinvasive strategy reduces mortality by 38% and reinfarction by 41% compared to delayed or ischemia-driven PCI 2

Rescue PCI Indications (Perform Immediately):

• <50% ST-segment resolution at 60-90 minutes 2, 7
• Persistent chest pain suggesting failed reperfusion 2
• Hemodynamic instability 2
• Electrical instability (ventricular arrhythmias) 2

Monitoring Requirements

Electrocardiographic Assessment:

• Obtain 12-lead ECG at 60-90 minutes post-administration to assess ST-segment resolution 2, 7
• ≥50% ST-segment resolution indicates successful reperfusion 4

Clinical Monitoring:

• Continuous cardiac monitoring for arrhythmias—have anti-arrhythmic therapy immediately available for bradycardia and ventricular irritability 3
• Monitor for signs of bleeding, particularly intracranial hemorrhage (altered mental status, severe headache, neurological deficits) 3, 4
• Assess for hypersensitivity reactions during and for several hours after administration 3
• Avoid intramuscular injections to minimize bleeding risk 3

Hemodynamic Surveillance:

• Monitor blood pressure, heart rate, and signs of heart failure or cardiogenic shock 1, 2
• Assess for recurrent ischemia (chest pain, ST-segment changes) 2

Special Clinical Scenarios

Extended Time Window (12-24 Hours):

• Tenecteplase may be considered if clinical/ECG evidence of ongoing ischemia exists with large myocardium at risk or hemodynamic instability when PCI unavailable (Class IIa recommendation) 1, 7
• Primary PCI remains strongly preferred in this timeframe 7

High-Risk Features Warranting Aggressive Approach:

• ≥2 mm ST-elevation in 2 anterior leads 2
• Systolic blood pressure <100 mmHg 2
• Heart rate >100 bpm 2
• Killip class II-III heart failure 2
• ≥2 mm ST-depression in anterior leads 2
• Right ventricular involvement 2

Cardiogenic Shock:

• Primary PCI is strongly preferred over fibrinolytic therapy regardless of time delay 2, 3

Key Clinical Advantages

Compared to Alteplase:

• Equivalent 30-day mortality 8, 9
• Significantly lower non-cerebral bleeding rates 8, 9
• Reduced need for blood transfusion 8
• Single-bolus administration reduces medication errors and nursing time 8
• Can be safely re-administered if re-occlusion occurs (no antibody formation) 8

Practical Implementation:

• Facilitates more rapid treatment in pre-hospital settings and rural hospitals 8
• Reduces door-to-needle time compared to 90-minute alteplase infusion 8