Sun14November1246PM 20

A 17-year-old male presents to the Emergency Department after an overdose of alcohol and paracetamol.

He complained of abdominal discomfort and an intravenous infusion of N-Acetylcysteine was commenced. Fifteen minutes later he developed breathlessness, reported feeling flushed, and developed a tachycardia.

Which of the following is the cause of this reaction?

(Please select 1 option)

The patient has received N-Acetylcysteine previously This is the correct answer

The patient has had a panic attack

A disulfiram-like (antabuse) reaction has occurred Incorrect answer selected

The patient has developed pulmonary oedema

The patient has received an overdose of N-Acetylcysteine

Explanation

This patient is having an acute hypersensitivity reaction the most common, dose independent adverse drug reaction. It is caused by previous exposure and being sensitised to the drug. The initial exposure induces the production of antibodies of Ig E class, subsequent exposure induces an immunological reaction - anaphylaxis. Some drugs can produce an similar pseudoallergic reaction on first exposure.

The majority of dose-related adverse reactions occur within the first hour of the initial infusion of acetylcysteine. The MHRA now recommends extending the time of the initial infusion from 15 minutes to 60 minutes in order to reduce the incidence of adverse reactions. Even if a patient has a history of a previous reaction to intravenous acetylcisteine, the benefits outweigh the risks and patient should receive treatment. Any 'hypersensitivity-like' reactions are more likely to be anaphylactoid in nature (i.e. not immunologically mediated) and therefore may not occur on repeated exposure.

Reference:

Medicines and Healthcare products Regulatory Agency (MHRA). Paracetamol overdose: new guidance on treatment with intravenous acetylcysteine.

Answer Statistics

1

49%

2

3%

3

39%

4

4%

5

6%

Times answered: 265