Allergy and immunology · core
Adult anaphylaxis
Adult anaphylaxis is treated first with intramuscular adrenaline 500 micrograms (0.5 mL of 1 in 1000) into the anterolateral mid-thigh. Antihistamines and corticosteroids are adjuncts. They do not open the airway or restore circulation.
Why this is high-yield for the UKMLA AKT
This is a classic UKMLA “do not delay the life-saving drug” stem. Candidates who remember ward-order sets (chlorphenamine, hydrocortisone, salbutamol) pick an adjunct first. The MLA emergency area tests whether you can name the dose, the dilution, and the site under time pressure.
The question
A 28-year-old woman is brought from a park after a bee sting. She is breathless and itchy. On examination she has stridor, a widespread urticarial rash, and a blood pressure of 78/46 mmHg. Her lips are swollen. She has no asthma history. A 16-gauge cannula is in situ. Oxygen is being given through a non-rebreather mask.
What is the most appropriate immediate drug treatment?
- A. Intravenous adrenaline 50 micrograms as a first bolus
- B. Intramuscular adrenaline 500 micrograms (0.5 mL of 1 in 1000) into the anterolateral thigh
- C. Intravenous chlorphenamine 10 mg
- D. Intravenous hydrocortisone 200 mg
- E. Nebulised salbutamol 5 mg
Reveal the worked answer
Correct answer: B. Intramuscular adrenaline 500 micrograms (0.5 mL of 1 in 1000) into the anterolateral thigh
A — IV adrenaline is reserved for peri-arrest or refractory anaphylaxis, given only by experienced clinicians with cardiac monitoring. First-line treatment in this still-perfusing adult is intramuscular adrenaline.
B (correct) — This is the BNF and Resuscitation Council UK adult dose and route: 500 micrograms IM (0.5 mL of 1 in 1000), anterolateral mid-thigh. Repeat after 5 minutes if there is no improvement.
C — An antihistamine may later help itch and rash. It does not treat airway obstruction or shock and must not delay adrenaline.
D — Corticosteroids are adjuncts. They have no role in the first minutes of anaphylaxis and must not displace IM adrenaline.
E — Bronchodilators can help wheeze once adrenaline is in, especially in people with asthma. This patient has stridor and hypotension — those are adrenaline indications, not a salbutamol-first picture.
Clinical pearl. Name three things in this order: drug, dose, site. Adrenaline, 500 micrograms IM, anterolateral thigh. Then ABC, fluids, and a second IM dose at 5 minutes if she is not improving.
MLA Content Map. Acute and emergency care · Anaphylaxis and allergy
Guideline. BNF treatment summary — Anaphylaxis (BNF Anaphylaxis)
Key facts to remember
- First-line adult anaphylaxis dose and route?
- Intramuscular adrenaline 500 micrograms (0.5 mL of 1 in 1000).
- Preferred injection site for IM adrenaline?
- Anterolateral mid-thigh.
- What is the role of chlorphenamine and hydrocortisone in anaphylaxis?
- Adjuncts only. They do not reverse airway or circulatory compromise and must not delay adrenaline.
- When do you give a second IM adrenaline dose?
- If there is no improvement after 5 minutes.
Frequently asked questions
What is the first-line treatment for adult anaphylaxis?
Intramuscular adrenaline 500 micrograms (0.5 mL of 1 in 1000) into the anterolateral mid-thigh, given immediately. Support the airway and circulation at the same time.
Can I give intravenous adrenaline first in anaphylaxis?
Not as routine first-line treatment. IV adrenaline is for peri-arrest or specialist-led refractory anaphylaxis with monitoring. This stem is an IM-first case.
Do steroids prevent a biphasic reaction?
Evidence that corticosteroids prevent biphasic reactions is weak. They remain adjuncts. The drug that treats the current reaction is intramuscular adrenaline.
Related learning paths
Educational content for exam preparation — always follow your local guidelines in practice. See our editorial standards.