What is the recommended dose of epinephrine (Epi) for an adult experiencing anaphylaxis via intramuscular (IM) or intravenous (IV) route?

Epinephrine Dosing for Adult Anaphylaxis

For adults with anaphylaxis, administer 0.3-0.5 mg of epinephrine 1:1000 (1 mg/mL) intramuscularly into the anterolateral thigh (vastus lateralis), repeating every 5-10 minutes as needed until symptoms resolve. 1, 2, 3

Intramuscular (IM) Administration - First-Line Treatment

Standard Dosing

• The recommended adult IM dose is 0.3-0.5 mg of 1:1000 epinephrine solution (equivalent to 0.3-0.5 mL), with a maximum single dose capped at 0.5 mg regardless of body weight. 1, 2, 3
• Inject into the anterolateral aspect of the mid-thigh (vastus lateralis muscle), which achieves peak plasma concentrations in 8±2 minutes compared to 34±14 minutes with subcutaneous deltoid injection. 1, 2
• Never inject into the buttocks, digits, hands, or feet due to risk of tissue injury. 3

Repeat Dosing Protocol

• Repeat the same dose every 5-10 minutes if symptoms fail to resolve or worsen—there is no maximum number of doses. 1, 2, 3
• The interval can be liberalized to permit more frequent injections (even more often than every 5 minutes) if clinically appropriate. 4, 1
• Approximately 10-20% of patients require more than one dose, with some requiring 3 or more doses before symptom recovery. 1, 2
• Fatalities in anaphylaxis result from delayed epinephrine administration, not from giving multiple doses—continue dosing until clinical improvement occurs. 1, 2

Critical Safety Points

• There are no absolute contraindications to epinephrine in anaphylaxis, even in elderly patients or those with cardiovascular disease—the risk of death from untreated anaphylaxis far exceeds any risk from epinephrine. 1, 2, 3
• The benefits of prompt epinephrine administration outweigh concerns about cardiac adverse effects in this life-threatening emergency. 1, 5

Intravenous (IV) Administration - Reserved for Specific Circumstances Only

When to Use IV Epinephrine

IV epinephrine should only be used in three specific situations: 2, 6

• Cardiac arrest
• Profound hypotension unresponsive to multiple IM doses and IV fluid resuscitation
• Complete failure to respond to several IM injections

IV Bolus Dosing (for graded reactions)

For perioperative or monitored settings with graded allergic reactions: 2

• Moderate hypotension/bronchospasm (Grade II): 20 mcg IV bolus, escalate to 50 mcg at 2 minutes if inadequate response
• Life-threatening hypotension/bronchospasm (Grade III): 50 mcg IV bolus (or 100 mcg if unresponsive to other vasopressors), escalate to 200 mcg at 2 minutes if needed
• Cardiac/respiratory arrest (Grade IV): 1 mg IV, repeat per advanced cardiac life support guidelines

IV Infusion Dosing

• Starting infusion rate: 1-4 mcg/min, titrated up to a maximum of 10 mcg/min based on clinical response. 4, 2, 6
• Preparation method: Add 1 mg (1 mL) of 1:1000 epinephrine to 250 mL of D5W to yield 4.0 mcg/mL concentration, then infuse at 15-60 drops/min with microdrop apparatus. 4, 2, 6
• Alternative preparation: Add 1 mg (1 mL) of 1:1000 epinephrine to 100 mL of saline (creating 1:100,000 solution), infuse at 30-100 mL/hr (5-15 mcg/min). 2, 6
• Continuous hemodynamic monitoring is mandatory when administering IV epinephrine. 2, 6

IV Safety Warnings

• Never use 1:1000 concentration intravenously—if IV administration is necessary, use 1:10,000 dilution (0.05-0.1 mg or 0.5-1 mL). 2
• IV epinephrine carries significant risk of dilution/dosing errors, potentially lethal arrhythmias, severe hypertension, and cerebral hemorrhage. 1, 6
• The IM route is safer and strongly preferred for first-line treatment. 1

Common Pitfalls to Avoid

• Delaying epinephrine administration is the leading cause of anaphylaxis fatalities—administer immediately upon recognition. 1, 2, 5
• Stopping at one dose prematurely when symptoms persist or progress—continue every 5 minutes as needed. 1
• Using antihistamines or corticosteroids as substitutes for epinephrine—these are only adjunctive therapies and do not prevent death. 2
• Confusing epinephrine concentrations—always use 1:1000 (1 mg/mL) for IM; 1:10,000 is reserved for IV use only. 1, 2
• Injecting into the deltoid or subcutaneously instead of the vastus lateralis—this delays peak plasma levels significantly. 1, 2

Concurrent Management

• Call 911 or activate the resuscitation team immediately upon recognizing anaphylaxis. 1, 2
• Position the patient supine with legs elevated; never allow standing or walking as this increases mortality risk. 1
• Administer high-flow oxygen and establish IV access for fluid resuscitation. 1
• For severe hypotension, give normal saline bolus of 1000-2000 mL for adults. 1
• Consider adjunctive therapies only after epinephrine: H1 antihistamines, H2 blockers (famotidine), and corticosteroids (hydrocortisone). 1

Pharmacologic Rationale

• Epinephrine has rapid onset within minutes but is quickly metabolized, making its effect short-lived and necessitating repeat dosing when initial response is inadequate. 1
• The number of doses should be determined by clinical response rather than an arbitrary maximum. 1
• Most patients show symptomatic improvement and systolic BP >90 mmHg within 5 minutes of appropriate epinephrine administration. 6