A 18-year-old male asked:
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will anti histamines such as zyrtec or allegra (fexofenadine) so on, effect methacholine since its a histmane and cause negative results?

1 doctor answer
Dr. John Chiu
Dr. John Chiu answered
56 years experience Allergy and Immunology
It may potentially: Antihistamines are not to be taken for at least 24 hrs but preferably 72 hrs prior a methacholine challenge. Having said that , I would doubt the average dose of AH is potent enough to block a truly positive response.
Answered on Mar 30, 2015

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