Adverse reactions to N-acetylcysteine

Area of Science:

• Pharmacology
• Clinical Toxicology
• Immunology

Background:

• N-acetylcysteine (Parvolex) is used clinically, but adverse reactions have been reported.
• The exact mechanism of these adverse reactions is not fully understood.

Purpose of the Study:

• To investigate the aetiology of adverse reactions to N-acetylcysteine (Parvolex).
• To differentiate between immunological and pseudo-allergic mechanisms.

Main Methods:

• Clinical case documentation of seven patients with adverse reactions.
• Intradermal skin testing with Parvolex, N-acetylcysteine, and ethylenediaminetetra-acetate in reactors and non-reactors.
• Assessment of reaction inhibition with terfenadine.

Main Results:

• Significantly greater weal responses to high concentrations of N-acetylcysteine (Parvolex) in patients who experienced adverse reactions (p < 0.02).
• No significant differences in responses to individual components (N-acetylcysteine, ethylenediaminetetra-acetate) between groups.
• Antihistamine (terfenadine) therapy inhibited reactions in two patients.

Conclusions:

• Adverse reactions to N-acetylcysteine (Parvolex) appear to be pseudo-allergic.
• The findings suggest a non-immunological mechanism for Parvolex-induced adverse events.