Sometimes  spirometry and inhaling bronchodilators can't show if you have asthma. Your physician may then ask you to take a methacholine challenge test. This test involves gradually exposing your lungs to an asthma trigger to see how responsive they are.
 

What is the Methacholine Challenge Test?

In this test, you’ll breathe in controlled doses of methacholine — a drug designed to tickle or irritate your airways. This test may cause shortness of breath, coughing or dizziness, so your pulmonary function technologist will monitor you closely while it’s administered.

How to Prepare for Your Test

You should:

• Avoid heavy exercise at least four hours prior to this test

• Don’t eat a heavy meal three hours before test

• Stop smoking three hours before test

• Don’t consume alcohol three hours before test

• Wear loose clothing that allows you to expand your chest (no tight belt or vest)

Your appointment may be rescheduled if you haven’t prepared according to these criteria.
 
Call us ahead of time if you:

• Have an inability to follow instructions*

• Have had a heart attack in the last month

• Have uncontrolled hypertension

• Are pregnant

• Are currently using cholinesterase inhibitor medication (e.g. myasthenia gravis)

• Are using beta-blockers (e.g. acebutolol, carteolol, labetalol, propranolol)

• Have chest or abdominal pain

• Have oral or facial pain

• Have had recent eye surgery (1 week to 6 months, depending on surgery)

• Have had recent brain surgery or an injury (3 to 6 weeks)

• Have had a collapsed lung (2 weeks)

• Are spitting up blood

 
*If a patient is unable to follow instructions due to a confused state, young age or dementia, then a parent, caregiver or guardian may call on their behalf.

Medications to Withhold Before Your Appointment

Do not take any of the following medications during the window of time outlined before your appointment:
                                                                                        

• Short-acting inhaled beta-agonists in conventional doses (e.g. albuterol): 6 hours

• Long-acting inhaled beta-agonists (e.g. salmeterol): 36 hours

• Ultra long-acting beta-agonists (e.g. indacaterol, vilanterol): 48 hours (2 days)

• Long-acting anticholinergics (e.g. tiotropium): 168 hours (7 days)

• Short-acting anticholinergics (e.g. Atrovent® 40 μg): 12 hours

• Oral theophylline: 12-24 hours