Methacholine: Difference between revisions

Latest revision as of 11:11, 23 March 2025

Methacholine[edit]

Methacholine is a synthetic choline ester that acts as a non-selective muscarinic receptor agonist in the parasympathetic nervous system. It is primarily used in the diagnosis of asthma through a test known as the methacholine challenge test.

Pharmacology[edit]

Methacholine is a quaternary ammonium compound, which means it carries a permanent positive charge. This characteristic limits its ability to cross the blood-brain barrier, thus reducing central nervous system effects. Methacholine mimics the action of the neurotransmitter acetylcholine by binding to muscarinic receptors, which are a subtype of acetylcholine receptors.

Mechanism of Action[edit]

Methacholine acts by stimulating muscarinic receptors, leading to the activation of the parasympathetic nervous system. This results in bronchoconstriction, increased bronchial secretions, and other effects typical of parasympathetic stimulation. The bronchoconstriction effect is utilized in the methacholine challenge test to assess airway hyperreactivity.

Clinical Use[edit]

Methacholine Challenge Test[edit]

The methacholine challenge test is a diagnostic tool used to evaluate airway hyperreactivity, which is a hallmark of asthma. During the test, the patient inhales increasing concentrations of methacholine aerosol. The degree of bronchoconstriction is measured using spirometry, specifically looking at the forced expiratory volume in one second (FEV1). A significant decrease in FEV1 indicates a positive test, suggesting the presence of asthma.

Side Effects[edit]

The administration of methacholine can lead to side effects due to its action on muscarinic receptors. Common side effects include:

Bronchoconstriction
Cough
Wheezing
Chest tightness
Headache
Dizziness

These effects are generally mild and resolve after the test is completed. However, in rare cases, severe bronchoconstriction can occur, necessitating the availability of bronchodilators and medical supervision during the test.

Contraindications[edit]

Methacholine should not be used in individuals with:

Severe asthma
Recent myocardial infarction
Uncontrolled hypertension
Known hypersensitivity to methacholine or other choline esters

Related Pages[edit]

@@ Line 1: / Line 1: @@
-'''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).
+== Methacholine ==
-==Pharmacology==
+[[File:Methacholine.svg|Methacholine chemical structure|thumb|right]]
-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 a synthetic choline ester that acts as a non-selective [[muscarinic receptor]] agonist in the [[parasympathetic nervous system]]. It is primarily used in the diagnosis of [[asthma]] through a test known as the methacholine challenge test.
-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==
+== Pharmacology ==
-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==
+Methacholine is a [[quaternary ammonium compound]], which means it carries a permanent positive charge. This characteristic limits its ability to cross the [[blood-brain barrier]], thus reducing central nervous system effects. Methacholine mimics the action of the neurotransmitter [[acetylcholine]] by binding to muscarinic receptors, which are a subtype of [[acetylcholine receptor|acetylcholine receptors]].
-* [[Bronchial challenge test]]
-* [[Muscarinic agonist]]
-* [[Parasympathomimetic drug]]
-==References==
+=== Mechanism of Action ===
-<references />
-[[Category:Drugs]]
+Methacholine acts by stimulating muscarinic receptors, leading to the activation of the [[parasympathetic nervous system]]. This results in bronchoconstriction, increased bronchial secretions, and other effects typical of parasympathetic stimulation. The bronchoconstriction effect is utilized in the methacholine challenge test to assess airway hyperreactivity.
-[[Category:Respiratory system]]
-[[Category:Pharmacology]]
-[[Category:Medicine]]
-{{stub}}
+== Clinical Use ==
-<gallery>
-File:Methacholine.svg|Methacholine
+=== Methacholine Challenge Test ===
-</gallery>
-<gallery>
+The methacholine challenge test is a diagnostic tool used to evaluate airway hyperreactivity, which is a hallmark of asthma. During the test, the patient inhales increasing concentrations of methacholine aerosol. The degree of bronchoconstriction is measured using spirometry, specifically looking at the [[forced expiratory volume]] in one second (FEV1). A significant decrease in FEV1 indicates a positive test, suggesting the presence of asthma.
-File:Methacholine.svg|Methacholine
-</gallery>
+== Side Effects ==
+The administration of methacholine can lead to side effects due to its action on muscarinic receptors. Common side effects include:
+* Bronchoconstriction
+* Cough
+* Wheezing
+* Chest tightness
+* Headache
+* Dizziness
+These effects are generally mild and resolve after the test is completed. However, in rare cases, severe bronchoconstriction can occur, necessitating the availability of bronchodilators and medical supervision during the test.
+== Contraindications ==
+Methacholine should not be used in individuals with:
+* Severe [[asthma]]
+* Recent [[myocardial infarction]]
+* Uncontrolled [[hypertension]]
+* Known hypersensitivity to methacholine or other choline esters
+== Related Pages ==
+* [[Asthma]]
+* [[Bronchoconstriction]]
+* [[Muscarinic receptor]]
+* [[Parasympathetic nervous system]]
+[[Category:Choline esters]]
+[[Category:Muscarinic agonists]]
+[[Category:Respiratory system diagnostic tests]]