Adrenaline (also known as epinephrine) is a sympathomimetic agent — it stimulates alpha- and beta-adrenergic receptors, making it ideal for treating life-threatening allergic reactions.

How It Works:

• Alpha-1 stimulation: Causes vasoconstriction → ↑ blood pressure, ↓ mucosal oedema (e.g., airway swelling)

• Beta-1 stimulation: Increases heart rate and cardiac output

• Beta-2 stimulation: Relaxes bronchial smooth muscle → relieves wheeze and bronchospasm

Together, these effects rapidly reverse the key features of anaphylaxis: hypotension, airway obstruction, and bronchospasm.

Age Group	Adrenaline Dose (IM)	Volume of 1:1000 Solution
Adult and children ≥12 years	500 micrograms	0.5 mL
Children 6–12 years	300 micrograms	0.3 mL
Children 6 months–6 years	150 micrograms	0.15 mL
Children under 6 months	100–150 micrograms	0.1–0.15 mL

Understanding Adrenaline 1:1000

• “1:1000” means:
  1 gram of adrenaline in 1000 mL, or
  1 mg in 1 mL

👉 So, 1 mL of 1:1000 adrenaline = 1 mg (1000 micrograms)

How Volume Is Calculated

To give a specific microgram dose, you draw up the matching volume from the 1 mg/mL (1:1000) solution:

Required Dose	How to Work It Out	Volume to Give
500 micrograms (0.5 mg)	500 ÷ 1000 = 0.5 mL	0.5 mL
300 micrograms (0.3 mg)	300 ÷ 1000 = 0.3 mL	0.3 mL
150 micrograms (0.15 mg)	150 ÷ 1000 = 0.15 mL	0.15 mL
100 micrograms (0.1 mg)	100 ÷ 1000 = 0.1 mL	0.1 mL

✅ Key Points to Remember

• Always use 1:1000 adrenaline (IM route only)

• The volume = dose in micrograms ÷ 1000

• Inject into the anterolateral thigh (middle outer thigh)

• Repeat after 5 minutes if no improvement.

Reference

https://www.resus.org.uk/sites/default/files/2021-05/Emergency%20Treatment%20of%20Anaphylaxis%20May%202021_0.pdf