How often can 0.5ml of 1:1000 adrenaline (epinephrine) be repeated in anaphylactic shock?

Intramuscular Adrenaline Dosing in Anaphylactic Shock

Intramuscular adrenaline 0.5 mL of 1:1000 (0.5 mg) should be repeated every 5 to 15 minutes as needed until symptoms resolve, with no maximum number of doses specified. 1, 2

Dosing Algorithm

Initial Dose

• Adults and children ≥30 kg: 0.3-0.5 mg (0.3-0.5 mL of 1:1000) IM into the anterolateral thigh 2
• The 0.5 mL dose represents the maximum single injection for adults 1, 2

Repeat Dosing Strategy

• Repeat every 5-10 minutes according to the FDA label 2 or every 5-15 minutes per American Heart Association guidelines 1
• Multiple doses are frequently required in severe hypotension or bronchospasm 1
• No upper limit exists on the number of doses that can be administered 1
• Monitor clinically for reaction severity and cardiac effects between doses 2

Critical Considerations

Route matters for safety: The intramuscular route is preferred over subcutaneous (slower onset) or intravenous (higher risk of adverse effects) administration 3. IM injection into the anterolateral thigh produces the most rapid peak plasma concentrations 1.

Avoid injection site necrosis: Do not administer repeated injections at the same anatomical site, as vasoconstriction can cause tissue necrosis 2.

When to escalate therapy: If several IM doses are required without adequate response, consider transitioning to an intravenous epinephrine infusion (5-15 μg/min) rather than continuing repeated boluses 1. This allows for more careful titration given epinephrine's short half-life 1.

Common Pitfalls

• Delaying repeat doses: Many patients require additional doses, with symptom recurrence after 5-15 minutes commonly reported 1. Do not hesitate to redose if symptoms persist or recur.

• Using inadequate needle length: For IM administration, use a needle at least 1/2 to 5/8 inch long to ensure intramuscular (not subcutaneous) delivery 2.

• Confusing concentrations: The question asks about 1:1000 concentration for IM use. Be aware that IV dosing uses 1:10,000 concentration at much lower volumes (0.05-0.1 mg or 0.5-1 mL of 1:10,000) 1.