Drugs acting on acetylcholine: boost it or block it?
Turn acetylcholine up, or turn it down — the organ decides what you see.
Select any card for the reasoning, what to watch for and an exam tip.
Drugs acting on acetylcholine
Acetylcholine crosses from the nerve ending to muscarinic receptors on the organ. Agonists act on the receptor themselves, anticholinesterases stop acetylcholine being broken down, and antimuscarinics sit in the receptor so acetylcholine can’t act.
- Nerve ending releases acetylcholine
- Acetylcholine (ACh) — anticholinesterases stop its breakdown, so there is more of it
- Muscarinic receptor on the organ — muscarinic agonists switch it on directly
- Antimuscarinic drug occupies the receptor — ACh can’t act
- Target organ: gland, smooth muscle or heart
Key points
- Boosters (agonists, anticholinesterases) cause sweating, salivation, a slow heart and gut cramps.
- Blockers cause the opposite: dry mouth, blurred vision, a fast heart, constipation and urinary retention.
- Antimuscarinic side-effects add up across drugs — STOPP flags two or more given together.
Key takeaway
Boosters make things wetter, slower and tighter; blockers make things drier, faster and looser — so each one’s side-effects are the other’s uses.