Intramuscular Epinephrine Should NOT Be Used for Cardiac Arrest
Intramuscular epinephrine is inappropriate for cardiac arrest and must never be used; the only acceptable route is intravenous or intraosseous administration of 1 mg (1:10,000 concentration) every 3-5 minutes. 1, 2, 3
Why Intramuscular Administration Fails in Cardiac Arrest
Absorption is unpredictable and inadequate during the low-flow or no-flow state of cardiac arrest, making IM delivery ineffective for achieving therapeutic plasma concentrations 4
The dose is insufficient – the 0.3-0.5 mg IM dose used for anaphylaxis is far below the 1 mg required for cardiac arrest resuscitation 2, 4
Immediate systemic delivery is essential during cardiac arrest because compromised peripheral perfusion prevents reliable drug absorption from muscle tissue 4
Correct Dosing Protocol for Cardiac Arrest
Administer 1 mg IV/IO epinephrine (1:10,000 concentration = 0.1 mg/mL) as the standard dose during adult cardiac arrest 1, 2, 3
Repeat every 3-5 minutes throughout the resuscitation until return of spontaneous circulation or termination of efforts 1, 2, 3
No maximum cumulative dose is defined in current guidelines, though the benefit of continued dosing beyond multiple rounds remains uncertain 3
This regimen improves return of spontaneous circulation (ROSC) and survival to hospital admission, though the impact on long-term neurologically intact survival remains controversial 1, 2
Critical Distinction: Anaphylaxis vs. Cardiac Arrest
For anaphylaxis WITHOUT cardiac arrest: Give 0.3-0.5 mg IM epinephrine (1:1000 concentration = 1 mg/mL) into the anterolateral thigh, repeated every 5-15 minutes as needed 2, 4
When anaphylaxis progresses to cardiac arrest: Immediately abandon the IM protocol and switch to the cardiac arrest regimen of 1 mg IV/IO epinephrine (1:10,000) every 3-5 minutes 2, 4
The 1:1000 concentration used for IM anaphylaxis is ten times more concentrated than the 1:10,000 formulation required for IV cardiac arrest dosing; confusing these can cause severe iatrogenic complications 4
High-Dose Epinephrine Is Not Recommended
High-dose epinephrine (0.1-0.2 mg/kg) is not recommended for routine use in cardiac arrest 3
While high-dose regimens may increase ROSC rates, they do not improve survival to hospital discharge and may worsen post-arrest outcomes through excessive vasoconstriction and myocardial injury 3
High-dose epinephrine may be considered only in exceptional circumstances such as beta-blocker or calcium channel blocker overdose 3
Pharmacokinetic Considerations
Epinephrine elimination during cardiac arrest is prolonged, with a half-life of approximately 2.6 minutes (range 1.9-4.4 minutes) 5
Repeated dosing may lead to accumulation and increased plasma levels, though the optimal plasma concentration during resuscitation remains unknown 5
The 3-5 minute dosing interval is based on expert consensus rather than pharmacokinetic data, and no evidence supports altering this interval to improve outcomes 6
Common Pitfalls to Avoid
Never use IM epinephrine for cardiac arrest – this route is reserved exclusively for anaphylaxis management 2, 4
Do not confuse concentrations – hospitals should stock clearly labeled, pre-filled syringes that differentiate IM (1:1000) from IV/IO (1:10,000) formulations 4
Avoid routine high-dose protocols without specific toxicological indications 3