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Pyridostigmine: Wikis


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Systematic (IUPAC) name
CAS number 155-97-5
ATC code N07AA02
PubChem 4991
DrugBank APRD00380
Chemical data
Formula C 9H13N2O2  
Mol. mass 181.212 g/mol
Pharmacokinetic data
Bioavailability 7.6 +/- 2.4%
Metabolism  ?
Half life 1.78 +/- 0.24hrs
Excretion Renal
Therapeutic considerations
Pregnancy cat. C(AU) C(US)
Legal status POM (UK) -only (US)
Routes Oral, intravenous
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Pyridostigmine is a parasympathomimetic and a reversible cholinesterase inhibitor. Since it is a quaternary amine, it is poorly absorbed in the gut and doesn't cross the blood-brain barrier, except possibly in stressful conditions.[1]


Mode of action

In a synapse, action potentials are conducted along motor nerves to their terminals where they initiate a Ca2+ influx and the release of acetylcholine (ACh). The ACh diffuses across the synaptic cleft and binds to receptors on the post synaptic membrane, causing an influx of Na+ and K+ ions, resulting in depolarisation. If large enough, this depolarisation results in an action potential. To prevent constant stimulation once the ACh is released, an enzyme called acetylcholinesterase is present in the endplate membrane close to the receptors on the post synaptic membrane, and quickly hydrolizes ACh.

Pyridostigmine inhibits acetylcholinesterase in the synaptic cleft, thus slowing down the hydrolysis of acetylcholine.

Clinical uses

Pyridostigmine is used to treat muscle weakness in people with myasthenia gravis and to combat the effects of curariform drug toxicity. Pyridostigmine bromide has been FDA approved for military use during combat situations as an agent to be given prior to exposure to the nerve agent Soman in order to increase survival. Used in particular during the first Gulf War, pyridostigmine bromide has been implicated as a causal factor in Gulf War syndrome[2].

Pyridostigmine is now also used to treat orthostatic hypotension.[3]

Pyridostigmine bromide is available under the trade names Mestinon (Valeant Pharmaceuticals) and Regonol.


Pyrostigmine bromide is contraindicated in cases of mechanical intestinal or urinary obstruction and should be used with caution in patients with bronchial asthma [4][5].

Side effects

Common side effects include[4]:

  • Nausea
  • Vomiting
  • Diarrhea
  • Abdominal cramps
  • Increased salivation
  • Tearing
  • Increased bronchial secretions
  • Constricted pupils


  1. ^ Gulf War Syndrome: More Complex Than Middle East Politics. JWatch Psychiatry 1997;1997:15-15.
  2. ^ Golomb, B. (2008) "Acetylcholinesterase inhibitors and Gulf War illnesses" Proc Natl Acad Sci; Reuters;
  3. ^ Gales BJ, Gales MA. (2007). "Pyridostigmine in the treatment of orthostatic intolerance". Ann Pharmacother. 41 (2): 314–8. doi:10.1345/aph.1H458. PMID 17284509.  
  4. ^ a b Mestinon | Home
  5. ^ Mestinon Official FDA information, side effects and uses

Related publications

  1. Brenner, G. M. (2000). Pharmacology. Philadelphia, PA: W.B. Saunders Company. ISBN 0-7216-7757-6
  2. Canadian Pharmacists Association (2000). Compendium of Pharmaceuticals and Specialties (25th ed.). Toronto, ON: Webcom. ISBN 0-919115-76-4
  3. Neal, M.J. (2002). Medical Pharmacology at a Glance (5th ed.). London, England: Blackwell Publishing. ISBN 1405133600

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