Chemical compound
Pharmaceutical compound
Methacholine (INN , USAN ) (trade name Provocholine ), also known as acetyl-β-methylcholine , is a synthetic choline ester that acts as a non-selective muscarinic receptor agonist in the parasympathetic nervous system .
Methacholine is primarily used to diagnose bronchial hyperreactivity ,[ 1] asthma and also occurs in chronic obstructive pulmonary disease . This is accomplished through the bronchial challenge test , or methacholine challenge, in which a subject inhales aerosolized methacholine, leading to bronchoconstriction . Other therapeutic uses are limited by its adverse cardiovascular effects, such as bradycardia and hypotension , which arise from its function as a cholinomimetic .
It is highly active at all of the muscarinic receptors, but has little effect on the nicotinic receptors . Methacholine has a charged quaternary amine structure, rendering it insoluble in lipid cell membranes . Clinically, this means that it will not cross the blood–brain barrier and has poor absorption from the gastrointestinal tract . It is broken down at a relatively slow rate within the body, due to its relative resistance to acetylcholinesterases .
The chemical structure of methacholine is derived from acetylcholine by the substitution of a methyl group on the β carbon ; this methyl group increases selectivity for muscarinic receptors over nicotinic receptors . The quaternary ammonium group is essential for activity.
Use of methacholine is contraindicated in patients with recent heart attack or stroke, uncontrolled hypertension, known severe airway disease, or aortic aneurysm. It may be used with caution by nursing or pregnant mothers and patients taking certain medications for myasthenia gravis .[ 2]
^ Birnbaum S, Barreiro TJ (June 2007). "Methacholine challenge testing: identifying its diagnostic role, testing, coding, and reimbursement". Chest . 131 (6): 1932– 5. doi :10.1378/chest.06-1385 . PMID 17565027 . ^ Valentin Popa (2001). "ATS guidelines for methacholine and exercise challenge testing". American Journal of Respiratory and Critical Care Medicine . 163 (1): 292– 293. doi :10.1164/ajrccm.163.1.16310b . PMID 11208661 .
mAChRs Tooltip Muscarinic acetylcholine receptors Agonists Antagonists
3-Quinuclidinyl benzilate 4-DAMP Aclidinium bromide (+formoterol )Abediterol AF-DX 250 AF-DX 384 Ambutonium bromide Anisodamine Anisodine Antihistamines (first-generation) (e.g., brompheniramine , buclizine , captodiame , chlorphenamine (chlorpheniramine) , cinnarizine , clemastine , cyproheptadine , dimenhydrinate , dimetindene , diphenhydramine , doxylamine , meclizine , mequitazine , perlapine , phenindamine , pheniramine , phenyltoloxamine , promethazine , propiomazine , triprolidine )AQ-RA 741 Atropine Atropine methonitrate Atypical antipsychotics (e.g., clozapine , fluperlapine , olanzapine (+fluoxetine ), rilapine , quetiapine , tenilapine , zotepine )Benactyzine Benzatropine (benztropine) Benzilone Benzilylcholine mustard Benzydamine Bevonium BIBN 99 Biperiden Bornaprine Camylofin CAR-226,086 CAR-301,060 CAR-302,196 CAR-302,282 CAR-302,368 CAR-302,537 CAR-302,668 Caramiphen Cimetropium bromide Clidinium bromide Cloperastine CS-27349 Cyclobenzaprine Cyclopentolate Darifenacin DAU-5884 Desfesoterodine Dexetimide DIBD Dicycloverine (dicyclomine) Dihexyverine Difemerine Diphemanil metilsulfate Ditran Drofenine EA-3167 EA-3443 EA-3580 EA-3834 Emepronium bromide Etanautine Etybenzatropine (ethybenztropine) Fenpiverinium Fentonium bromide Fesoterodine Flavoxate Glycopyrronium bromide (+beclometasone/formoterol , +indacaterol , +neostigmine )Hexahydrodifenidol Hexahydrosiladifenidol Hexbutinol Hexocyclium Himbacine HL-031,120 Homatropine Imidafenacin Ipratropium bromide (+salbutamol )Isopropamide J-104,129 Hyoscyamine Mamba toxin 3 Mamba toxin 7 Mazaticol Mebeverine Meladrazine Mepenzolate Methantheline Methoctramine Methylatropine Methylhomatropine Methylscopolamine Metixene Muscarinic toxin 7 N-Ethyl-3-piperidyl benzilate N-Methyl-3-piperidyl benzilate Nefopam Octatropine methylbromide (anisotropine methylbromide) Orphenadrine Otenzepad (AF-DX 116) Otilonium bromide Oxapium iodide Oxitropium bromide Oxybutynin Oxyphencyclimine Oxyphenonium bromide PBID PD-102,807 PD-0298029 Penthienate Pethidine pFHHSiD Phenglutarimide Phenyltoloxamine Pipenzolate bromide Piperidolate Pirenzepine Piroheptine Pizotifen Poldine Pridinol Prifinium bromide Procyclidine Profenamine (ethopropazine) Propantheline bromide Propiverine Quinidine 3-Quinuclidinyl thiochromane-4-carboxylate Revefenacin Rociverine RU-47,213 SCH-57,790 SCH-72,788 SCH-217,443 Scopolamine (hyoscine) Scopolamine butylbromide (hyoscine butylbromide) Silahexacyclium Sofpironium bromide Solifenacin SSRIs Tooltip Selective serotonin reuptake inhibitors (e.g., femoxetine , paroxetine )Telenzepine Terodiline Tetracyclic antidepressants (e.g., amoxapine , maprotiline , mianserin , mirtazapine )Tiemonium iodide Timepidium bromide Tiotropium bromide Tiquizium bromide Tofenacin Tolterodine Tricyclic antidepressants (e.g., amitriptyline (+perphenazine ), amitriptylinoxide , butriptyline , cidoxepin , clomipramine , desipramine , desmethyldesipramine , dibenzepin , dosulepin (dothiepin) , doxepin , imipramine , lofepramine , nitroxazepine , northiaden (desmethyldosulepin) , nortriptyline , protriptyline , quinupramine , trimipramine )Tridihexethyl Trihexyphenidyl Trimebutine Tripitamine (tripitramine) Tropacine Tropatepine Tropicamide Trospium chloride Typical antipsychotics (e.g., chlorpromazine , chlorprothixene , cyamemazine (cyamepromazine) , loxapine , mesoridazine , thioridazine )Umeclidinium bromide (+vilanterol )WIN-2299 Xanomeline Zamifenacin
Precursors prodrugs )
