Epinephrine Dosing in Adult Anaphylaxis
In adult anaphylaxis, epinephrine can be administered every 5-10 minutes as necessary until symptoms resolve, with no absolute maximum number of doses. 1
Initial Dosing and Administration
- The recommended initial dose for adults is 0.3-0.5 mg (0.3-0.5 mL of 1:1000 solution) administered intramuscularly into the anterolateral aspect of the thigh 1
- Intramuscular injection into the thigh (vastus lateralis) is superior to subcutaneous or intramuscular injection into the arm (deltoid) 2
- There is no absolute contraindication to epinephrine administration in anaphylaxis 2
Repeat Dosing
- Epinephrine can be repeated every 5-10 minutes as necessary if symptoms persist 1
- The 5-minute interval between injections can be liberalized to permit more frequent injections if clinically needed 2
- Studies have shown that 8-28% of patients with anaphylaxis require two or more doses of epinephrine 3
- Development of toxicity or inadequate response to epinephrine injections indicates that additional therapeutic modalities are necessary 2
Intravenous Epinephrine
IV epinephrine should only be administered in specific circumstances: 4
- Cardiac arrest
- Profound hypotension unresponsive to IV fluids and IM epinephrine
- Failure to respond to several injected doses of epinephrine
For IV administration (when necessary), options include: 2, 4
- Add 1 mg (1 mL) of 1:1000 epinephrine to 250 mL of D5W (concentration 4.0 mcg/mL)
- Initial infusion rate: 1-4 mcg/min, increasing to maximum of 10 mcg/min
- Alternative: Add 1 mg (1 mL) of 1:1000 epinephrine to 100 mL saline (1:100,000 solution)
- Initial rate: 30-100 mL/h (5-15 mcg/min), titrated based on response
Important Considerations
- Fatalities during anaphylaxis usually result from delayed administration of epinephrine 2
- Continuous hemodynamic monitoring is essential when administering IV epinephrine 4
- Potential adverse effects include tachyarrhythmias, hypertension, and risk of potentially lethal arrhythmias 4
- Antihistamines and glucocorticoids should never be administered before or in place of epinephrine 2
Common Pitfalls to Avoid
- Delaying epinephrine administration - this is associated with increased mortality 5
- Injecting into buttocks, digits, hands, or feet - these are inappropriate injection sites 1
- Using subcutaneous route - this has delayed onset of action compared to IM 5
- Relying solely on antihistamines - these are second-line agents and should never replace epinephrine 2
- Administering IV epinephrine without appropriate monitoring - this increases risk of potentially lethal arrhythmias 2
Remember that while there is no maximum number of doses specified in guidelines, the need for multiple doses indicates severe anaphylaxis requiring close monitoring and possibly additional interventions beyond epinephrine.