Epinephrine IM 1 mg/mL (1:1,000) | Medication Reference

Bedside Snapshot

Drug Class: Endogenous catecholamine; nonselective α- and β-adrenergic agonist
Life-Saving Use: First-line treatment for anaphylaxis—give IM into the mid-outer thigh as soon as anaphylaxis is suspected; do not delay for IV access or other therapies
Adult Anaphylaxis Dose: 0.3–0.5 mg IM (0.3–0.5 mL of 1 mg/mL) in the anterolateral thigh; may repeat every 5–15 minutes as needed based on symptoms and blood pressure
Pediatric Anaphylaxis Dose: 0.01 mg/kg IM (0.01 mL/kg of 1 mg/mL) to a usual maximum of 0.3 mg per dose in smaller children; some guidelines allow up to 0.5 mg in larger adolescents; repeat every 5–15 minutes if symptoms persist or worsen
Common Autoinjector Strengths: 0.1 mg (small infants), 0.15 mg (pediatric ~7.5–25/30 kg), 0.3 mg (≥25/30 kg), and 0.5 mg (≥45–50 kg); device-specific weight cutoffs vary by country and guideline
Site and Route Matter: IM injection into the mid-outer thigh achieves faster and higher peak levels than subcutaneous injection or IM injection into the deltoid; this route is preferred in all major guidelines
Onset: Typically within 3–5 minutes, with peak clinical effect within ~5–10 minutes; effects on airway edema, bronchospasm, and perfusion may need repeated dosing and adjunctive therapies (fluids, oxygen, bronchodilators, adjunctive pressors)
No Absolute Contraindications in Anaphylaxis: There are essentially no absolute contraindications to IM epinephrine in true anaphylaxis; the risk of undertreatment is far greater than the risk of adverse cardiovascular events, even in older patients or those with coronary disease
Common Transient Effects: Tremor, palpitations, anxiety, pallor, mild headache at therapeutic doses
Serious Effects (Uncommon): Arrhythmias, severe hypertension, ischemia are uncommon with IM dosing but may occur in high-risk patients

Brand & Generic Names

Generic Name: Epinephrine (also known as adrenaline internationally)
Brand Names: Adrenalin, EpiPen, Auvi-Q, Jext, Emerade, others; availability is region- and institution-specific

Medication Class

Endogenous catecholamine; nonselective α- and β-adrenergic agonist

Pharmacology

Mechanism of Action (IM use in anaphylaxis/asthma):

Epinephrine is a nonselective adrenergic agonist with activity at α1, α2, β1, and β2 receptors
α1-adrenergic effects: Peripheral vasoconstriction, which increases systemic vascular resistance and blood pressure; counters vasodilation and increased vascular permeability in anaphylaxis; reduces mucosal edema in the upper airway
β1-adrenergic effects: Increased heart rate, contractility, and conduction velocity, supporting cardiac output and improving perfusion during distributive shock and hypotension
β2-adrenergic effects: Bronchodilation, inhibition of mediator release from mast cells and basophils, and promotion of intracellular potassium uptake; β2 effects are key for reversing bronchospasm and limiting ongoing anaphylactic mediator release
IM administration into the thigh provides rapid absorption and high peak levels while avoiding the abrupt plasma spikes and higher arrhythmia risk associated with IV bolus dosing
In asthma exacerbations, subcutaneous or IM epinephrine can be used as a rescue agent when inhaled β2-agonists are ineffective or unavailable, leveraging similar β2-mediated bronchodilation

Pharmacokinetics – IM Epinephrine:

Absorption: IM injection into the anterolateral thigh results in more reliable and rapid absorption than subcutaneous injection or IM injection at other sites; peak plasma concentrations are generally reached within ~5–10 minutes in most studies
Distribution: Epinephrine is rapidly distributed to highly perfused organs (heart, lungs, brain) with an apparent volume of distribution of ~0.2–0.5 L/kg; highly water soluble; does not cross the blood–brain barrier significantly but does cross the placenta
Metabolism: Primarily metabolized by catechol-O-methyltransferase (COMT) and monoamine oxidase (MAO) in liver, kidney, and other tissues to inactive metabolites (metanephrine, vanillylmandelic acid)
Elimination: Metabolites are renally excreted; plasma half-life of epinephrine is short (minutes), but clinical effects can persist longer due to receptor signaling cascades and ongoing pathophysiology (e.g., ongoing anaphylactic mediator release)
Special considerations: In shock states with poor peripheral perfusion, IM absorption may be delayed or erratic; repeated IM dosing and early consideration of IV infusion in a monitored setting are recommended if response is inadequate

Indications

First-line treatment of anaphylaxis of any cause (foods, medications, venoms, latex, idiopathic, etc.) in outpatient, prehospital, ED, and inpatient settings
Initial management of severe allergic reactions at high risk of progression to anaphylaxis (e.g., rapidly progressive urticaria/angioedema with respiratory or cardiovascular symptoms)
Rescue treatment for severe asthma exacerbations when inhaled β2 agonists are ineffective, unavailable, or cannot be delivered (e.g., impending respiratory failure in resource-limited settings)
Treatment of anaphylaxis associated with immunotherapy, radiocontrast, biologic infusions, and perioperative exposures

Dosing & Administration

Available Forms:

Vials/ampoules: 1 mg/mL (1:1,000) epinephrine solution for IM/subcutaneous use; typically 1 mL or 30 mL multi-dose vials
Autoinjectors: Pre-filled devices delivering fixed doses (0.1 mg, 0.15 mg, 0.3 mg, 0.5 mg) via automatic IM injection into the thigh
Note: 1:1,000 (1 mg/mL) concentration is for IM/subcutaneous use only; IV epinephrine requires different dilution (see separate Epinephrine IV 1:10,000 reference)

Concentration Critical: Always verify concentration before administration. IM/subcutaneous epinephrine uses 1:1,000 (1 mg/mL). IV epinephrine uses 1:10,000 (0.1 mg/mL) or diluted infusions. Administering concentrated 1:1,000 epinephrine IV can cause catastrophic cardiovascular events.

Standard Dosing – IM Epinephrine (1 mg/mL, 1:1,000):

Indication / Population	Dose & Concentration	Route & Frequency	Notes / Maximum
Adult anaphylaxis (≥~30 kg)	0.3–0.5 mg (0.3–0.5 mL of 1 mg/mL)	IM into mid-outer thigh; repeat every 5–15 min as needed	Most labels cap single IM dose at 0.5 mg; no fixed limit on number of doses if symptoms persist and BP allows
Pediatric anaphylaxis (<~30 kg)	0.01 mg/kg (0.01 mL/kg of 1 mg/mL); usual max 0.3 mg per dose	IM into mid-outer thigh; repeat every 5–15 min if persistent symptoms	Autoinjector options: 0.1 mg, 0.15 mg, 0.3 mg depending on weight; check local guideline cutoffs
Severe asthma exacerbation (rescue; specialist use)	0.01 mg/kg IM (max 0.5 mg)	May repeat every 20 min × 3 doses in some protocols	Reserved for severe/life-threatening cases where inhaled β2 agonists are ineffective or unavailable

Administration Technique: Inject IM into the anterolateral thigh (vastus lateralis muscle). This site provides more rapid and reliable absorption than deltoid or subcutaneous injection. Autoinjectors are designed for thigh use and can be administered through clothing in emergencies.

Contraindications

Absolute/Functional Contraindications (True Anaphylaxis):

Essentially none. In genuine anaphylaxis, IM epinephrine should not be withheld for relative concerns (age, pregnancy, CAD, arrhythmias). The risk of undertreating anaphylaxis far outweighs the cardiovascular risk of appropriate IM dosing

Major Precautions (Contextual):

Underlying coronary artery disease, structural heart disease, or significant arrhythmias: Risk of ischemia or arrhythmia is higher but still outweighed by the need to treat anaphylaxis; monitor closely and consider early IV access in monitored setting
Pregnancy: Epinephrine remains first-line for maternal anaphylaxis, with dosing similar to non-pregnant adults; maternal stabilization is key for fetal outcomes
Concurrent β-blocker therapy: Response to epinephrine may be blunted; consider adjunctive glucagon and aggressive supportive care in refractory cases
Extremes of age: Frail elderly and very small infants—use weight-based dosing (0.01 mg/kg) and guideline-based autoinjector selection; monitor closely for tachycardia, hypertension, and arrhythmias

Adverse Effects

Common (usually transient at typical IM doses):

Tremor, anxiety, and a sense of "impending doom"
Palpitations, tachycardia, and mild hypertension
Headache, dizziness, and pallor
Nausea or vomiting

Serious (rare at appropriate IM doses):

Supraventricular or ventricular arrhythmias: Especially in older patients with structural heart disease or with very high doses
Severe hypertension: Possible intracranial hemorrhage or myocardial ischemia in susceptible individuals
Tissue ischemia/necrosis: With accidental injection into fingers, hands, or toes (from autoinjectors); may require phentolamine infiltration
Worsening bronchospasm or paradoxical reactions: Extremely rare but reported
Pulmonary edema: Rare; can occur after multiple doses or in patients with underlying cardiac dysfunction

Special Populations

Pediatrics: Use weight-based dosing (0.01 mg/kg IM); autoinjector selection based on weight cutoffs (typically 0.15 mg for 15–30 kg, 0.3 mg for ≥30 kg); may repeat every 5–15 minutes as needed
Pregnancy: Epinephrine is first-line for anaphylaxis in pregnancy; maternal stabilization takes priority; no dose adjustment needed; monitor both maternal and fetal status
Older adults: Use standard adult dosing (0.3–0.5 mg IM); increased monitoring for cardiovascular effects (hypertension, ischemia, arrhythmias); benefits outweigh risks in true anaphylaxis
Patients on β-blockers: May have blunted response to epinephrine; consider higher or repeated doses; glucagon (1–2 mg IV/IM) can be used as adjunct to overcome β-blockade
Renal/hepatic impairment: No specific dose adjustment for IM epinephrine in anaphylaxis; metabolism occurs in multiple tissues

Monitoring Parameters – IM Epinephrine in Anaphylaxis

Airway, breathing, circulation: Stridor, wheeze, work of breathing, mental status, pulses, blood pressure, and capillary refill
Heart rate, rhythm, and blood pressure: At baseline and after each dose when feasible; continuous monitoring for moderate/severe reactions
Signs of progression or refractory anaphylaxis: Persistent hypotension, airway edema, bronchospasm, or shock despite 2–3 IM doses and fluids → escalate to IV infusion and critical care support
Need for adjunctive therapies: Oxygen, IV fluids, inhaled β2 agonists, antihistamines, corticosteroids, and vasopressors as per guidelines
Documentation: Timing, dose, route, site, and response to each epinephrine administration

Clinical Pearls

When in doubt, give epinephrine: Delayed or omitted IM epinephrine is one of the most common and dangerous errors in anaphylaxis management. If you suspect anaphylaxis, administer epinephrine immediately—do not wait for confirmatory signs or IV access.

Use the mid-outer thigh and IM route: Avoid subcutaneous injection, which has slower and less predictable absorption, especially in shock. The anterolateral thigh (vastus lateralis) provides the most rapid and reliable absorption.

Autoinjectors vs vials: Autoinjectors are ideal for community/prehospital use, but in the ED/ICU, drawing up from a 1 mg/mL vial allows precise weight-based dosing for children and higher doses (0.5 mg) for larger adults when indicated.

Transition to IV infusion: If multiple IM doses are required or perfusion is poor, prepare to transition to an IV epinephrine infusion in a monitored setting while continuing IM dosing as needed during setup.

Documentation importance: Document timing, dose, route, site, and response to each epinephrine administration—this matters for ongoing management and medico-legal review.

β-blocker interference: Patients on β-blockers may have blunted response to epinephrine. Consider glucagon 1–2 mg IV/IM as an adjunct—glucagon works through non-adrenergic pathways and can help overcome β-blockade to improve cardiac output and bronchodilation.

Biphasic reactions: Up to 20% of anaphylaxis cases can have biphasic reactions with symptom recurrence 4–12 hours after initial resolution. All patients receiving epinephrine for anaphylaxis should be observed for at least 4–6 hours (longer if severe or high-risk features present).

Concentration confusion kills: Never administer 1:1,000 epinephrine IV—this concentration is for IM/subcutaneous use only. IV administration requires 1:10,000 dilution or continuous infusion preparations. Always verify concentration and route before administration.

References

1. Dalal, R., Zhukovsky, S., & Dodd, A. (2024). Epinephrine. In StatPearls [Internet]. StatPearls Publishing. https://www.ncbi.nlm.nih.gov/books/NBK482160/
2. Dodd, A., Hughes, A., Sargant, N., et al. (2021). Evidence update for the treatment of anaphylaxis. Clinical and Translational Allergy, 11(4), e12084. https://doi.org/10.1002/clt2.12084
3. Frith, K., & colleagues. (2021). Updated anaphylaxis guidelines: Management in infants and children. Archives of Disease in Childhood: Education & Practice Edition, 106(4), 222–231. https://doi.org/10.1136/archdischild-2020-319471
4. Morriello, F., & Bilo, M. B. (2023). Epinephrine in anaphylaxis. Current Treatment Options in Allergy, 10, 1–15. https://doi.org/10.1007/s40521-023-00323-5
5. U.S. Food and Drug Administration. (2023). ADRENALIN (epinephrine injection) 1 mg/mL prescribing information. DailyMed. https://dailymed.nlm.nih.gov