UMEM Educational Pearls

Title: Anaphylatoid reaction to IV N-acetylcysteine

Keywords: anaphylactoid reaction, IV NAC (PubMed Search)

Posted: 9/13/2018 by Hong Kim, MD, MPH (Emailed: 9/14/2018)
Click here to contact Hong Kim, MD, MPH

Analphylatoid reaction is caused by non-IgE mediated histamine released. Intravenous N-acetylcysteine (NAC) infusion is well known to cause analphylatoid reaction. However, it’s incidence is unknown.

Recently, a large retrospective study of all patients who received 21-hour IV NAC in 34 Canadian hospitals (1980 to 2005) was performed.

Anaphylactoid reaction was documented in 528 (8.2%) of 6455 treatment courses

Cutaneous reaction (urticarial, pruritus and angioedema) occurred in 398 (75.4%)
Systemic reaction (respiratory symptoms or hypotension): 34 (6.4%)
Both reactions: 96 (18.2%)

Over 90% patients developed analphylatoid reaction within 5 hours.

Onset of reaction:

1^stNAC dosing (150 mg/kg over 1 hour): 133/528
2^ndNAC dosing (50 mg/kg over 4 hours): 371/528
3^rdNAC dosing (100 mg/kg over 16 hours): 24/528

Administered medication for treatment

Antihistamine: 371
Beta-2 agonist: 15
Epinephrine: 10
Corticosteroids: 7

Patient characteristics that were associated with higher incidence of Anaphylactoid reaction includes

Female
Single acute ingestion
Low serum acetaminophen level.

Bottom line

Anaphylactoid reaction to NAC is uncommon
Cutaneous symptoms are most common
Female, single acute ingestion and low serum acetaminophen levels are associated with incidence of anaphylactoid reaction.

References

Yarema M et al. Anaphylactoid reactions to intravenous N-acetylcysteine during treatment for acetaminophen poisoning. J Med Toxicol 2018: Jun;14(2):120-127. doi: 10.1007/s13181-018-0653-9. Epub 2018 Feb 8.