Anaphylaxis to NAC

Healthy female treated with NAC for paracetamol overdose
The patient goes on to have the infusion of acetylcysteine.
10 minutes later you are called to her with the following set of observations.
RR36
Sats 89% Air
BP 80/40
There is no lip or tongue swelling. She is wheezy. She has chest tightness.

Her observations had previously been all normal. What is the most likely diagnosis?

  • Acute severe asthma
  • Upper GI bleed
  • Epiglottitis
  • Myocardial infarction
  • Anaphylaxis

Acetlycysteine can commonly cause adverse events including anaphylaxis.
In this situation where a person has been relatively well shortly beforehand this is the most likely diagnosis.
During anaphylaxis common symptoms are:
Syncope/ wheezing/ stridor/ abdominal pain/ collapse/ breathlessness/ rash
The infusion should be stopped and emergency treatment instigated using the ABC approach.