Methacholine

Methacholine (also known as Mecholyl) is a synthetic choline ester that acts as a non-selective muscarinic receptor agonist in the parasympathetic nervous system. It is primarily used to diagnose bronchial hyperreactivity, which is the hallmark of asthma and also occurs in chronic obstructive pulmonary disease (COPD).

Pharmacology

Methacholine is a parasympathomimetic that stimulates muscarinic receptors in the airways to provoke bronchoconstriction. This action can be blocked by anticholinergic drugs. Methacholine has a longer duration of action than acetylcholine due to its resistance to breakdown by acetylcholinesterase.

Clinical use

Methacholine is used in a Methacholine challenge test to identify bronchial hyperreactivity. This test involves the inhalation of increasing concentrations of methacholine, monitoring for a 20% drop in the Forced expiratory volume (FEV1). If the patient is sensitive to methacholine, they will react to lower concentrations.

Side effects

Possible side effects of methacholine include coughing, chest tightness, wheezing, shortness of breath, and headache. These effects are usually mild and go away on their own.

See also

• Bronchial challenge test
• Muscarinic agonist
• Parasympathomimetic drug

References

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