Medicine & USMLE


  1. Bethanechol
  2. Carbachol
  3. Methacholine
  4. Pilocarpine
  5. Donepezil Rivastigmine and Galantamine
  6. Edrophonium
  7. Neostigmine
  8. Physostigmine
  9. Pyridostigmine


Bethanechol is a muscarinic agonist or cholinomimetic drug often used in the treatment of ileus and nonobstructive urinary retention due to its ability to induce GI and bladder contraction. Its side effects are primarily related to it’s parasympathetic activity and include “wet” symptoms such as diaphoresis.

Key Points

  • Bethanechol
    • Mechanism
      • Agonist at muscarinic receptors
        • Activates M3 receptors in the GI and urinary tracts to induce smooth muscle contractions
    • Clinical Use
      • Urinary retention and ileus (e.g. post-op)
        • M3 receptor signaling activates bowel and bladder smooth muscle
    • Adverse Effects
      • Diaphoresis
        • Sweat glands have muscarinic receptors and are therefore activated by acetylcholine, in addition to sympathetic innervation
      • Bronchoconstriction
        • May lead to exacerbation of asthma/COPD
      • Increased gastric acid production
        • Exacerbations of peptic ulcers via acetylcholine signaling