Medical Pharmacology Chapter 6:  Autonomic Pharmacology: Cholinergic Drugs

• Cholinergic Agents

  • Choline Esters

    • Acetylcholine

    • Bethanechol (Urecholine)

    • Carbachol

    • Methacholine (Provocholine)

  • Alkaloids

    • Muscarine

    • Pilocarpine (Pilocar)

• Clinical Uses

  • Gastrointestinal and Genitourinary

    • Bethanechol (Urecholine) 

      •  GI smooth muscle stimulant

        • Postoperative abdominal distention

        • Paralytic ileus

        • Esophageal reflux; promotes increased esophageal motility (other drugs are more effective, e.g. dopamine antagonist (metoclopramide) or serotonin agonists (cisapride)

      •  Urinary bladder stimulant

        • Post-operative; post-partum urinary retention

      • Alternative to pilocarpine to treat diminished salivation secondary, for example. to radiation

      • Carbachol not used due to more prominent nicotinic receptor activation

    • Methacholine used for diagnostic purposes.

      • Testing for bronchial hyperreactivity and asthma

  • Opthalmological Uses 

    • Acetylcholine and Carbachol may be used for intraocular use as a miotic in surgery

    • Carbachol may be used also in treatment of glaucoma. 

    • Pilocarpine is used in management of glaucoma and has become the standard initial drug for treating the open-angle form.

    • Sequential adminstration of atropine (mydriatic) and pilocarpine (miotic) is used to break iris-lens adhesions.

• Major contraindication to the use of muscarinic agonists

  • Asthma: Choline esters (muscarinic agonists) can produce bronchoconstriction. In the predisposed patient, an asthmatic attack may be induced.

  • Hyperthyroidism: Choline esters (muscarinic agonists) can induce atrial fibrillation in hyperthyroid patients.

  • Peptic ulcer: Choline esters (muscarinic agonists), by increasing gastric acid secretion, may exacerbate ulcer symptoms.

  • Coronary vascular disease:  Choline esters (muscarinic agonists), as a result of their hypotensive effects, can further compromise coronary blood flow.

•   Adverse Effects: Muscarinic Agonists 

  • Salivation

  • Diaphoresis

  • Colic

  • GI hyperactivity

  • Headache

  • Loss of visual accommodation

Brown, J.H. and Taylor, P. Muscarinic Receptor Agonists and Antagonists, In, Goodman and Gillman's The Pharmacological Basis of Therapeutics, (Hardman, J.G, Limbird, L.E, Molinoff, P.B., Ruddon, R.W, and Gilman, A.G.,eds) The McGraw-Hill Companies, Inc.,1996, pp.149-150.