A Methacholine challenge is a test to determine if you have asthma. It is performed by inhaling a medication (methacholine) in increasing doses in an attempt to produce a change in your pulmonary function test results.
- The test will continue until you reach at least a 20% drop in your FEVI (the amount of air you exhale in the first second) or you finish all the dosages of the medication.
- After the testing is completed, you may be given a nebulizer treatment that will reverse the action of the methacholine, if it has caused your results to change.
- After each dose and after the breathing (nebulizer) treatment, you will be asked to perform several breathing tests.
- The testing time varies and may take up to 2 hours, depending on how you do.
- You may have some mild shortness of breath from taking the medication. True asthma attacks are very rare and generally respond promptly to treatment.
Prior to coming in for testing, you will be asked not to take some of your morning medications:
The following medications need to be avoided 48 hours prior to testing.
- Oral bronchodilators–Slobid, Theodur, Uniphyll, Unidur, Theophylline
- Antihistamines–Claritin (regular and D), Allegra (regular and D), Benadryl, Bromfed, Atrohist, and over-the counter cold, cough and sinus medications.
The following medications need to be avoided 24 hours prior to testing.
- Oral steroids–Prednisone, Medrol, Methylpredisolone
- Oral bronchodilators–Proventil Repetabs
The following medications need to be avoided 12 hours prior to testing:
- Bronchodilators–Albuterol, Ventoline, Proventil, Maxair, Brethaire, Serevent, Atrovent, Combivent
Avoid all caffeine 6 hours prior to testing.
NORMAL DIET – no fasting is necessary