Synopsis
Recognise medicine-related harm, assess severity and causality, treat urgent reactions and communicate accurate adverse-reaction information to prevent recurrence.
- Assess and treat the patient before completing a causality score or reporting form. The next action is determined by physiological severity as well as the suspected mechanism.
- For adult anaphylaxis, give adrenaline 500 micrograms intramuscularly into the anterolateral thigh, using 0.5 mL of 1 mg/mL solution; repeat after 5 minutes if airway, breathing or circulation problems persist.
- Stop the suspected infusion or exposure when feasible, call for help and use an ABCDE approach. Antihistamines and corticosteroids do not replace adrenaline for life-threatening anaphylaxis.
Key red flags
Airway swelling, breathing difficulty or circulatory compromise after medicine exposure requires immediate emergency assessment and treatment for possible anaphylaxis.
Fever with a painful widespread rash, blistering, mucosal involvement or systemic organ symptoms after a new medicine needs urgent assessment for a severe delayed reaction.
Reasoning priorities
Assess severity and identify threats requiring treatment now.
Use airway assessment, respiratory observations, pulse, pressure, consciousness and other indicated bedside tests. Do not wait for a laboratory result to treat anaphylaxis. In a suspected pharmacological reaction, glucose or ECG assessment may rapidly identify the mechanism of collapse or confusion.
Worked reasoning
A 42-year-old receiving an IV co-amoxiclav dose develops widespread urticaria, wheeze and throat tightness within minutes. Blood pressure is 78/46 mmHg and oxygen saturation 90%. Adrenaline 1 mg/mL is available, and no adrenaline has yet been given.
- Recognise airway/breathing and circulatory compromise consistent with anaphylaxis. Stop the suspected infusion, call the emergency team and assess ABCDE. Position safely, usually lying flat with legs raised if tolerated; adapt for breathing difficulty and do not allow sudden standing.
- Calculate the intramuscular adrenaline volume: 500 micrograms equals 0.5 mg; 0.5 mg divided by 1 mg/mL equals 0.5 mL. Administer 500 micrograms IM into the anterolateral thigh promptly, alongside oxygen and the required resuscitation support.
- Reassess airway, breathing and circulation and repeat the IM dose after 5 minutes if problems persist. Obtain senior help, IV access and further anaphylaxis-pathway treatment as needed; antihistamines are not the first treatment for this hypotensive wheezing patient.
- Give the final immediate action as IM adrenaline and continuing emergency reassessment. Independently check the ampoule concentration, microgram-to-milligram conversion and 0.5 mL volume, then record administration time and response. After stabilisation, arrange observation, reaction documentation, indicated tests and specialist follow-up.
A stable patient reports a new symptom after a medicine or regimen change.