Parasympathomimetics

Products

Parasympathomimetics are commercially available in the form of tablets, capsules, solutions, transdermal patches, injectable solutions, and eye drops, among others.

Structure and properties

Many parasympathomimetics are structurally related to the natural ligand acetylcholine.

Effects

Parasympathomimetics have cholinergic (parasympathomimetic) properties. They promote the effects of the parasympathetic nervous system, a portion of the autonomic nervous system. Direct parasympathomimetics bind as agonists to muscarinic and/or nicotinic acetylcholine receptors. Indirect parasympathomimetics (cholinesterase inhibitors) inhibit the breakdown of the natural neurotransmitter acetylcholine by inhibiting the enzyme acetylcholinesterase. This increases the local concentration of acetylcholine. Parasympathomimetics exert the following effects, among others:

  • Pupil constriction
  • Secretory stimulation: sweat, salivary, lacrimal glands, exocrine glands of the digestive tract, mucous cells of the respiratory tract
  • Reduction of heart rate
  • Stimulation of the smooth muscle of the intestinal tract.
  • Tonus increase of the bronchial musculature
  • Tonus and the motility increase of the urogenital tract, bile ducts and gallbladder.
  • Promotion of urinary bladder emptying

Indications

Indications for use of parasympathomimetics (selection):

Dosage

According to the SmPC. Parasympathomimetics are administered both systemically and topically.

Active ingredients

Direct parasympathomimetics (receptor agonists):

  • Acetylcholine (miochol).
  • Bethanechol chloride (myocholine-Glenwood)
  • Carbachol (Miostat)
  • Muscarine (not on the market)
  • Pilocarpine (Spersacarpine, Salagen)

Indirect parasympathomimetics (cholinesterase inhibitors):

Contraindications

Full precautions can be found in the drug label.

Interactions

When parasympathomimetics are combined, adverse effects may be increased. Conversely, parasympatholytics may reduce the effects. The effects of muscle relaxants may be antagonized.

Adverse effects

Possible adverse effects include:

  • Central disturbances, headache
  • Bradycardia (slow heart rate), vasodilatation, drop in blood pressure.
  • Bronchospasm and muscle spasms
  • Diarrhea, abdominal cramps, gastrointestinal hyperactivity.
  • Increased salivation, indigestion.
  • Visual disturbances, pupil constriction.
  • Sweating
  • Urinary urgency, urinary incontinence