Loading medications and dose in mi
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"myocardial infarction" AND "loading dose" AND antiplatelet
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Loading Medications and Doses in Myocardial Infarction (MI)
The table below covers the major drug categories used acutely in STEMI/NSTEMI, with loading doses where applicable.
1. Antiplatelet Agents
| Drug | Loading Dose | Maintenance | Notes |
|---|---|---|---|
| Aspirin (ASA) | 162-325 mg PO (chewed/crushed) or PR | 81 mg/d indefinitely | Non-enteric-coated preferred for rapid absorption; 325 mg preferred if ASA-naive |
| Clopidogrel | 600 mg PO (PCI strategy) 300 mg PO (fibrinolytic strategy, within 24 h) | 75 mg/d x 12 months | No loading dose in patients >75 y receiving fibrinolytics. 600 mg preferred if >24 h after fibrinolytic |
| Prasugrel | 60 mg PO | 10 mg/d x 12+ months | Contraindicated if prior stroke/TIA; avoid in age >75 y or weight <60 kg. Give only after coronary anatomy defined (within 1 h of PCI) |
| Ticagrelor | 180 mg PO | 90 mg BID x 12+ months | Preferred P2Y12 for ACS - mortality benefit over clopidogrel. Maintenance ASA must be ≤100 mg/d |
| Cangrelor | 30 mcg/kg IV bolus | 4 mcg/kg/min infusion | IV P2Y12; FDA-approved for PCI in patients who haven't received an oral P2Y12 |
Dual antiplatelet therapy (DAPT) = ASA + one P2Y12 inhibitor for all ACS patients.
2. Anticoagulants
| Drug | Dose | Notes |
|---|---|---|
| Unfractionated Heparin (UFH) | 60 units/kg IV bolus (max 4,000 units), then 12 units/kg/h (max 1,000 units/h), titrate PTT to 1.5-2.5x control | Preferred for PCI - real-time monitoring with ACT; give to all PCI patients and fibrinolytic recipients (except streptokinase) |
| Enoxaparin (LMWH) | 30 mg IV bolus, then 1 mg/kg SC q12h | Patients >75 y: no loading dose, reduce to 0.75 mg/kg SC BID; if last dose >8 h before PCI, give additional 0.3 mg/kg bolus; hold if creatinine >2.5 (men) or >2.0 (women) mg/dL |
| Fondaparinux | 2.5 mg SC | Used in fibrinolytic strategy; not for use as sole anticoagulant in primary PCI |
| Bivalirudin | 0.75 mg/kg IV bolus, then 1.75 mg/kg/h infusion | Agent of choice in HIT. Alternative to UFH + GPIIb/IIIa; lower bleeding but higher stent thrombosis rate |
3. Fibrinolytic (Thrombolytic) Agents
Used when primary PCI is unavailable within 120 min (door-to-balloon goal).
| Drug | Dose |
|---|---|
| Alteplase (tPA) | 15 mg IV bolus; then 0.75 mg/kg over 30 min (max 50 mg); then 0.5 mg/kg over 60 min (max 35 mg). Total max = 100 mg |
| Tenecteplase (TNK-tPA) | Single IV bolus, weight-based: 30 mg (<60 kg) / 35 mg (60-69 kg) / 40 mg (70-79 kg) / 45 mg (80-89 kg) / 50 mg (≥90 kg) |
| Reteplase | 10 units IV over 2 min, then repeat 10 units IV bolus 30 min later |
| Streptokinase | 1.5 million units over 60 min (no heparin required after) |
4. Glycoprotein IIb/IIIa Inhibitors
Used selectively in high-risk PCI (large thrombus, STEMI, high-risk ACS) - not routine.
| Drug | Loading Dose | Infusion |
|---|---|---|
| Abciximab | 0.25 mg/kg IV bolus | 0.125 mcg/kg/min (max 10 mcg/min) x 12-24 h |
| Eptifibatide | 180 mcg/kg IV bolus | 2.0 mcg/kg/min x 72-96 h |
| Tirofiban | 0.4 mcg/kg/min x 30 min | 0.1 mcg/kg/min x 48-96 h |
5. Anti-ischemic / Supportive Agents
| Drug | Dose | Key Contraindications |
|---|---|---|
| Nitroglycerin (SL) | 0.4 mg SL q5 min x 3 PRN chest pain | SBP <90 mmHg, HR >100 or <50, RV infarct, PDE-5 inhibitor use within 48 h |
| Nitroglycerin (IV) | Start 10 mcg/min, titrate up (10% MAP reduction if normotensive; 30% if hypertensive) | Same as above |
| Morphine | 2-5 mg IV q5-15 min PRN refractory pain | Use with caution - may mask ischemic symptoms; associated with worse outcomes in NSTEMI |
| Beta-blockers (oral) | e.g., Metoprolol tartrate 25-50 mg PO | Start within 24 h; avoid if HF, cardiogenic shock, SBP <120, HR <60 or >110, age >70, advanced heart block |
| Beta-blocker (IV) | Reserved only for arrhythmia/acute hypertension | Can increase mortality in STEMI; do NOT use for sinus tachycardia |
| Supplemental O₂ | If SpO₂ <90% | - |
Quick Summary: STEMI Loading Sequence
- ASA 325 mg (chewed) immediately
- P2Y12 inhibitor loading dose (ticagrelor 180 mg preferred, or clopidogrel 600 mg, or prasugrel 60 mg)
- Anticoagulant (UFH bolus 60 units/kg if going to PCI; enoxaparin 30 mg IV if fibrinolytic)
- Nitroglycerin SL for pain, morphine if refractory
- Oral beta-blocker within 24 h if no contraindications
- Reperfusion (primary PCI goal <90 min; fibrinolytic if PCI unavailable within 120 min)
Sources: The Washington Manual of Medical Therapeutics; Tintinalli's Emergency Medicine; Harrison's Principles of Internal Medicine 22E; Braunwald's Heart Disease.
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