Pyridostigmine
An oral anticholinesterase, longer acting than neostigmine, used mainly to strengthen weak muscles in myasthenia gravis.
Drug card
- Class
- Anticholinesterase
- How it works
- Blocking acetylcholinesterase, so acetylcholine builds up at synapses
- Used for
- Myasthenia gravis
- Reversing non-depolarizing muscle relaxants (injection)
- Protection against soman nerve agent (military use)
- Known for
- Abdominal cramps and pain
- Cholinergic crisis in overdose
- Its name
- -stigmine means a cholinesterase inhibitor
Study it as a flashcard, and it comes back before you forget it.
Mechanism of action
How does pyridostigmine work?
A quaternary carbamate that binds reversibly to acetylcholinesterase, like neostigmine. Slowing acetylcholine breakdown eases transmission at the neuromuscular junction and strengthens muscles weakened by myasthenia gravis. It lasts longer and stirs up the gut less than neostigmine, and the kidneys clear it mostly unchanged.
Like other anticholinesterases: They bind reversibly to acetylcholinesterase and block it, so acetylcholine is broken down more slowly and builds up at synapses. At the neuromuscular junction the extra acetylcholine strengthens weak muscles in myasthenia gravis and outcompetes non-depolarizing blockers. It also boosts muscarinic effects on the gut, glands, airways and heart, which cause most side effects.
Uses
What is pyridostigmine used for?
- Myasthenia gravis
- Reversing non-depolarizing muscle relaxants (injection)
- Protection against soman nerve agent (military use)
Side effects
Side effects of pyridostigmine
- Abdominal cramps and painKnown for
- Cholinergic crisis in overdoseKnown forSerious
- Diarrhea
- Nausea and vomiting
- Excess saliva
- Sweating
- Muscle cramps and twitching
- Airway narrowing and bronchial secretionsSerious
- Small pupils (miosis)
- Slow heart rate
- Passing urine often
- Skin rash from the bromide
Known for marks what an exam expects you to know it for.
Watch for
Cautions and what sets it apart
- Contraindicated in mechanical obstruction of the gut or urinary tract.
- Asthma or COPD: used with particular care, as it narrows the airways.
- Kidney disease: lower doses may be needed, since it is excreted mainly unchanged in urine.
- Growing weakness can mean overdose (cholinergic crisis), not worse myasthenia, and the two need opposite treatment.
Good to know: Longer acting than neostigmine with fewer gut effects, and taken by mouth, so it suits long-term treatment of myasthenia gravis.
Remember it
A way to remember it
DUMBBELSS
- D
- Diarrhea
- U
- Urination
- M
- Miosis
- B
- Bradycardia
- B
- Bronchospasm and bronchial secretions
- E
- Emesis (vomiting)
- L
- Lacrimation (watery eyes)
- S
- Salivation
- S
- Sweating
A mnemonic widely used in teaching
Its name
-stigmine means cholinesterase inhibitor
Neostigmine reverses non-depolarizing muscle relaxants and rivastigmine treats dementia. Donepezil, a cholinesterase inhibitor used for dementia, doesn't carry the stem.
- Every drug name stem
Its class
Anticholinesterases
Other anticholinesterases with a card:
Easily mixed up with direct-acting muscarinic agonists and cholinesterase inhibitors for dementia.
Sources
Checked against
Written for biofideX in plain words, after checking these references:
- Pyridostigmine bromide tablets: label (DailyMed)
- Pyridostigmine bromide injection: label (DailyMed)
- Pyridostigmine bromide for soman pretreatment: label (DailyMed)
- Pyridostigmine bromide (NCI Thesaurus)
For learning pharmacology, not for treatment decisions: no doses are given, and a prescriber, pharmacist or the product's own label is the word on any one patient. Spotted a mistake? Tell us and we'll correct it.
Autonomic nervous system
Pyridostigmine is one of 10 drugs practiced together here: their classes, how they work, what they treat and what they're known for.
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