The Methacholine Challenge is a test to see if you have airways sensitivity or not. Airways sensitivity may be caused by inflammation of the airways, making it difficult to breathe sometimes. Methacholine is an agent that, when inhaled, causes the airways to spasm (contract involuntarily) and narrow if asthma is present.
A trained Respiratory Physiologist will ask you to breathe in the Methacholine, using a disposable nebulizer mouthpiece. As part of the test, you will be asked to blow into a tube that will measure the effect of this substance on your lungs. This medicine is only used to see whether you have airways sensitivity.
Approximately: 60 minutes
You may generally continue with your normal routine. However, there are some points to note to improve comfort and ensure accurate results:
Some Drugs will interfere with the Methacholine Challenge. Please do not take the following medication before the test:
- Inhaled non-steroidal anti-inflammatory agents 6-8 hours prior testing
- Salbutamol, Salamol (Short-Acting β2 Agonists) 8 Hours prior testing
- Atrovent or Combivent (Ipratropium bromide) 12 hours prior testing
- Fluticasone, Symbicort (inhaled corticosteroids plus β2 Agonists) 24 hours prior testing
- Salmeterol, formoterol (Long-Acting β2 Agonists), Theophyline, 24 hours prior testing
- Spiriva, Respimat (Tiotropium Bromide), Antihistamines, 72 hours prior testing
- Montelukast (Leukotriene – Receptor Antagonists) 4 days prior testing
Some food interactions: Ingestion of significant quantities of coffee, tea, cola drinks, chocolate or other foods containing caffeine may decrease bronchial responsiveness and should be totally avoided on the day of the test.
Smoking and vigorous exercise should not be undertaken on the day of the test.
You will be asked to sit comfortably on a chair. Initially you will be asked to blow forcefully into a tube (spirometry test). You will be asked to inhale a mist that contains different concentrations of Methacholine.
During this test, you inhale increasing amounts of methacholine aerosol mist before and after spirometry. The mist is produced by a device called nebulizer and inhaled through a mouthpiece. Next you will be asked to blow forcefully into the tube again. This test measures the effect of the Methacholine on your lungs. The previous steps described may be repeated up to 10 times with more and more Methacholine depending on the effect on your lungs, until the test is finished.
Once the test has finished you will always be given a medicine (Bronchodilator) to help you breathe.
This test does not cause an asthma attack but the inhalation of the Methacholine for people who do have airway sensitivity their airways will become narrower and so they may find it harder to breathe. Also symptoms of cough, chest tightness, wheezing, chest soreness or headache can occur. Many subjects do not have symptoms at all. These symptoms (if they occur) are mild, last for only a few minutes, and disappear following the inhalation of a bronchodilator medication.
- If you have any of the following please call us to discuss:
- Unstable angina
- A recent pneumothorax (air trapped beneath the chest wall)
- A recent heart attack or stroke
- Recent eye or abdominal surgery
- Coughed up blood recently and the cause is not known
- Known hypersensitivity to mannitol or gelatin used to make capsules
- Conditions that may be compromised by induced bronchospasm or repeated spirometry maneuvers
- High blood pressure
- Nursing mothers Patients 6-18 years of age, due to limited information on the use of Osmohale in this population.