Muscarinic antagonist

• Dry mouth, constipation, urinary retention, blurred vision, ↑ heart rate (M2)
• Bronchodilation (inhaled), mydriasis/cycloplegia (ophthalmic)
• If BBB-crossing: confusion, memory impairment, delirium
• ↓ drug-induced EPS by restoring striatal dopamine–ACh balance

Muscarinic antagonist (1/4)

• Confusion, memory problems
• Increased dementia risk with chronic anticholinergic burden
• Dry mouth < M3
• Possible sedative effects
• Anti-parkinsonian, treatment of EPS
• ➔ rationale: EPS occurs when the balance between dopaminergic and cholinergic activity is disrupted
• Increased heart rate
• ➔ M2 blockade at SA node → removal of vagal tone

Muscarinic antagonist (2/4)

• Medications for overactive bladder (OAB)
• Mydriasis (dilated pupils) and cycloplegia
• Bronchodilation

Muscarinic antagonist (3/4)

• Decreased gastric acid secretion
• ➔ older antimuscarinics were used for peptic ulcer disease in the pre-PPI era
• Dry mouth
• Decreased bowel motility → constipation
• May impair pancreatic insulin release and worsen glucose regulation
• Increased striatal dopamine signaling
• ➔ may contribute to anti-parkinsonian effects (M1 predominant)
• ➔ possible contributor to anticholinergic delirium

Muscarinic antagonist (4/4)

• No selective M4 antagonist is available
• No established effects attributable to selective M5 blockade

Drugs with this mechanism (69)

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