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Anaphylactic reactions associated with trimethoprim

A M Bijl1, M M Van der Klauw, A C Van Vliet

  • 1Drechtsteden Hospital, Dordrecht, The Netherlands.

Abstract

Insights

Anaphylaxis, a severe allergic reaction, can be caused by trimethoprim, an component of cotrimoxazole. This finding suggests trimethoprim-induced anaphylaxis may be more common than previously recognized.

Area of Science:

  • Pharmacology
  • Immunology
  • Drug Safety

Background:

  • Anaphylactic reactions to cotrimoxazole are typically attributed to its sulphamethoxazole component.
  • The potential for trimethoprim to cause anaphylaxis remains less understood.

Purpose of the Study:

  • To investigate whether the trimethoprim component of cotrimoxazole can elicit anaphylactic reactions.
  • To assess the frequency and causality of trimethoprim-induced anaphylaxis.

Main Methods:

  • Analysis of case reports of anaphylaxis attributed to trimethoprim submitted to the Dutch Inspectorate for Health Care's Drug Safety Unit.
  • Classification of reported cases based on the probability of a causal relationship between trimethoprim exposure and anaphylaxis.

Main Results:

  • Thirteen reports of anaphylaxis linked to trimethoprim were received between September 1981 and November 1995.
  • Nine cases were classified as probable anaphylaxis (3 definite, 6 probable causal link).
  • Four cases were classified as possible anaphylaxis (1 definite, 3 probable causal link).

Conclusions:

  • Anaphylaxis caused by trimethoprim, while seemingly rare, may occur more frequently than previously assumed.
  • This suggests that not all anaphylactic reactions to cotrimoxazole are solely due to the sulphamethoxazole component.

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