Epinephrine Dosing: Allergic Reactions vs. Cardiac Emergencies
For anaphylaxis, give 0.2-0.5 mg (1:1000) intramuscularly into the thigh every 5-15 minutes; for cardiac arrest, give 1 mg (1:10,000) intravenously every 3-5 minutes—the dose is 10-fold higher and the route is different in cardiac emergencies. 1, 2
Anaphylaxis/Allergic Reactions (Non-Arrest)
First-Line Treatment
- Dose: 0.2-0.5 mg (adult) or 0.01 mg/kg up to 0.3 mg (child <30 kg)
- Concentration: 1:1000 (1 mg/mL)
- Route: Intramuscular into anterolateral thigh (preferred)
- Repeat interval: Every 5-15 minutes as needed
- Rationale: IM administration into the thigh produces rapid peak plasma concentrations and is safer than IV in non-arrest situations 1, 2
Alternative IV Dosing (Anaphylactic Shock with IV Access)
When a patient has profound hypotension/shock with IV access already established:
- Dose: 0.05-0.1 mg (5-10% of cardiac arrest dose)
- Concentration: 1:10,000 (0.1 mg/mL)
- Route: Slow IV push or infusion at 5-15 μg/min
- Critical distinction: This is dramatically lower than cardiac arrest dosing to avoid potentially lethal arrhythmias 1
Cardiac Arrest (Including Anaphylaxis-Induced Arrest)
Standard Dosing
- Dose: 1 mg (10-fold higher than anaphylaxis IM dose)
- Concentration: 1:10,000 (0.1 mg/mL)
- Route: Intravenous or intraosseous
- Repeat interval: Every 3-5 minutes (operationally, every second CPR cycle after initial dose)
- Timing in shockable rhythms: Administer after initial defibrillation attempts, not before 3
Key Principle
Once a patient progresses to cardiac arrest—even from anaphylaxis—standard ACLS dosing (1 mg IV/IO every 3-5 minutes) takes priority over anaphylaxis-specific dosing 1
Critical Safety Considerations
The 10-Fold Error Risk
This is a high-risk area for fatal medication errors. Physicians frequently confuse the dosing between anaphylaxis and cardiac arrest, leading to iatrogenic overdoses when cardiac arrest doses (1 mg IV) are given for anaphylaxis 4, 5. The consequences include:
- Severe systolic dysfunction
- Ventricular arrhythmias
- Potentially lethal cardiac complications
Preventing Errors
- Stock prefilled, clearly labeled IM syringes (0.3-0.5 mg) in crash carts specifically for anaphylaxis 4
- Remember: 1:1000 = IM for anaphylaxis; 1:10,000 = IV for cardiac arrest
- Never give the 1 mg cardiac arrest dose IV push to a patient with anaphylaxis who still has a pulse 6, 4
Clinical Decision Algorithm
Step 1: Is there a pulse?
- YES → Anaphylaxis dosing (0.2-0.5 mg IM, 1:1000)
- NO → Cardiac arrest dosing (1 mg IV/IO, 1:10,000)
Step 2: If pulse present, is there IV access and profound shock?
- NO IV or stable → Continue IM dosing every 5-15 minutes
- YES, with shock → Consider low-dose IV (0.05-0.1 mg slow push or 5-15 μg/min infusion) with continuous hemodynamic monitoring 1
Step 3: If cardiac arrest develops during anaphylaxis treatment
- Immediately switch to standard ACLS protocol: 1 mg IV/IO every 3-5 minutes 1
Additional Context
Why the Difference?
The 10-fold dose difference reflects fundamentally different pathophysiology:
- Anaphylaxis: Vasodilatory shock requiring vasoconstriction and bronchodilation; lower doses achieve this without excessive cardiac stimulation
- Cardiac arrest: Absent circulation requiring maximal alpha-adrenergic vasoconstriction to generate coronary perfusion pressure; beta-2 receptor activation may also help restore cardiac function 7
Repeat Dosing Reality
Over 35% of anaphylaxis patients require more than one epinephrine dose, with 72% of severe (Grade III) reactions needing multiple doses 8. This underscores the importance of having multiple doses readily available and monitoring patients for 4-8 hours minimum, as symptoms can recur.
Shockable Rhythms in Cardiac Arrest
In cardiac arrest with shockable rhythms (VF/pulseless VT), prioritize rapid defibrillation first; give epinephrine after initial defibrillation attempts fail 3. In non-shockable rhythms, early epinephrine is appropriate.