Metacholine, also known as acetyl-beta-methylcholine chloride, is a synthetic cholinergic agent that mimics the action of acetylcholine (ACh) in the body.

Chemical Structure:

• Molecular Formula: C8H18ClNO2
• Chemical Name: 2-[(Acetoxy)(methyl)amino]ethyltrimethylammonium chloride

Pharmacological Effects:

• Stimulates muscarinic receptors, producing:
  • Bronchoconstriction
  • Increased salivation and sweating
  • Pupil constriction (miosis)
  • Increased gastrointestinal motility and secretion
  • Urinary bladder contraction

Clinical Uses:

• Diagnostic tool for bronchial hyperreactivity and asthma
• Used in bronchial challenge tests to assess airway responsiveness
• Research applications in studying cholinergic systems

Side Effects:

• Bronchospasm and respiratory distress
• Coughing and wheezing
• Nausea, vomiting, and diarrhea
• Headache, dizziness, and weakness
• Hypersalivation, sweating, and flushing

Contraindications:

• Asthma and other respiratory conditions (except for diagnostic purposes)
• Peptic ulcer disease
• Hyperthyroidism
• Pregnancy and lactation
• Hypotension and cardiac arrhythmias

Note: Metacholine is a potent cholinergic agent and should be used with caution, under medical supervision.