Reversible cholinesterase inhibitor Pregnancy: Safety in pregnancy not established; experience in pregnant myasthenic patients has revealed no untoward effect on the course of pregnancy. Crosses the placenta — avoid excessive doses and monitor the newborn for possible effects. IV administration can induce uterine contraction (especially in late pregnancy). Only negligible amounts excreted in breast milk.

Pyridostigmine bromide

Brand names: Mestinon

Pyridostigmine bromide is an oral acetylcholinesterase inhibitor used for symptomatic treatment of myasthenia gravis.

Auto-extracted from the source labelling — not yet independently clinician-verified. These values were distilled from the UK SPC (or the US label where noted) but have not had a clinician sign-off. Confirm against the current SmPC before prescribing.

Adult dose

Dose: Myasthenia gravis: 30 to 120 mg per dose

Route: Oral

Frequency: At intervals throughout the day when maximum strength is needed (e.g. on rising and before mealtimes); duration of action 3-4 hours in the daytime, up to 6 hours for a bedtime dose

Myasthenia gravis (adults): total daily dose usually in the range of 5-20 tablets (each tablet 60 mg pyridostigmine bromide), but higher doses may be needed according to dose titration. Paralytic ileus and post-operative urinary retention (adults): usual dose 1-4 tablets (60-240 mg) per day, frequency varied to patient need. Paediatric myasthenia gravis (not a per-kg dose): children under 6 years initial 30 mg (half a tablet), children 6-12 years 60 mg (one tablet), increased gradually in 15-30 mg daily increments; total daily requirements usually 30-360 mg. Paediatric paralytic ileus / urinary retention: 15-60 mg per day. Verify paediatric dosing against a children's formulary. Take with water.

Dose adjustments

Renal

Pyridostigmine is mainly excreted unchanged by the kidney; lower doses may be required in patients with renal disease and treatment should be based on titration of dosage to effect.

Dose auto-extracted from UK Summary of Product Characteristics (SPC) via the eMC; US FDA prescribing information (openFDA / DailyMed) — cross-check; US labelling may differ from UK — not yet clinician-verified. Always confirm against the product SmPC and your local formulary before prescribing.

Contraindications

Hypersensitivity to the active substance, bromides or to any of the excipients
Mechanical gastro-intestinal or urinary obstruction

Side effects

Muscarinic: nausea, vomiting, diarrhoea, abdominal cramps, increased peristalsis, increased bronchial secretion, salivation, bradycardia, miosis
Nicotinic: muscle spasms, fasciculation, muscular weakness
Arrhythmia (including bradycardia, tachycardia, AV block), Prinzmetal angina, syncope, hypotension
Increased lacrimation, accommodation disorders (e.g. blurred vision)
Rash, hyperhidrosis, urticaria; drug hypersensitivity

Interactions

Corticosteroids / immunosuppressant drugs: requirement for pyridostigmine may be decreased (a new addition of corticosteroids may initially aggravate myasthenia gravis symptoms)
Methylcellulose (and medicines containing it as an excipient) can completely inhibit absorption of pyridostigmine
Atropine and hyoscine antagonise the muscarinic effects; slower GI motility from these drugs may affect pyridostigmine absorption
Non-depolarising muscle relaxants (e.g. pancuronium, vecuronium): pyridostigmine antagonises their effect; may prolong the effect of depolarising relaxants (e.g. suxamethonium)
Aminoglycoside antibiotics, local and some general anaesthetics, antiarrhythmic agents and other drugs interfering with neuromuscular transmission may interact

Clinical monograph

How it works

It reversibly inhibits acetylcholinesterase at the neuromuscular junction, increasing acetylcholine availability and improving neuromuscular transmission.

Prescribing in practice

Excessive dosing can precipitate a cholinergic crisis with weakness that mimics myasthenic worsening, so deterioration must be assessed carefully before increasing the dose.
Cholinergic adverse effects include abdominal cramps, diarrhoea, salivation and bradycardia, and caution is needed in asthma, bradycardia and peptic ulcer disease.
Use with caution and reduced exposure in renal impairment as it is largely renally excreted.

Monitoring

Monitor muscle strength and symptom control, heart rate and muscarinic side effects, distinguishing under- from over-treatment.

Counselling the patient

Take doses on time, as timing relative to meals and activity can affect symptom control.
Report increasing weakness, excessive salivation, cramps or diarrhoea.
Seek urgent help if breathing or swallowing becomes difficult.

Evidence & guidelines

Pyridostigmine is an established first-line symptomatic treatment for myasthenia gravis.

Reference: ABN guidelines; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

Curated clinical cross-links plus same-class fallbacks.

Calculators

Pathways