Reason for switching
Considerations for switching
- neostigmine- parenteral injections
- pyridostigmine- oral solution or tablets
Neostigmine formulations are licensed for different therapeutic indications.
- Intramuscular or subcutaneous neostigmine is licensed for myasthenia gravis.
- Intravenous neostigmine is licensed for reversal of non-depolarising neuromuscular blockage. This route will not be covered as this page focuses on switching between neostigmine and pyridostigmine in myasthenia gravis.
All oral formulations of pyridostigmine are licensed for myasthenia gravis. Use pyridostigmine liquid in people with swallowing difficulty or enteral feeding tubes.
60mg oral pyridostigmine is equivalent to 1 to 1.5mg intramuscular or subcutaneous neostigmine.
- The prescribed dose of parenteral neostigmine or oral pyridostigmine for myasthenia gravis is correct.
- The healthcare professional has considered factors affecting the choice of the medicine (for example: cautions, contraindications and medicine interactions).
- The individual is aged 12 years or over.
Duration of action
Pyridostigmine has a slower onset of action and longer duration of action versus neostigmine so the dosing interval of pyridostigmine may be longer compared to neostigmine.
Switching from pyridostigmine to neostigmine
There are no formal studies on switching from oral pyridostigmine to parenteral neostigmine. The switching advice below is based on established dosing equivalence referenced in standard medical literature.
Doses of 30 to 120mg are given at suitable intervals throughout the day. The interval may depend on times when symptoms are worse e.g. on rising.
Confirm the route and indication with the prescriber. Using the equivalence factor, switch the oral pyridostigmine dose to parenteral neostigmine.
- 60mg oral pyridostigmine is equivalent to 1 to 1.5mg intramuscular or subcutaneous neostigmine.
Give neostigmine parenterally.
Repeat the intramuscular or subcutaneous neostigmine dose at appropriate intervals throughout the day e.g. 2 to 4 hourly.
A 30-year-old lady takes 60mg pyridostigmine four times a day for myasthenia gravis. The prescriber would like to switch to subcutaneous neostigmine. The method of calculating the subcutaneous neostigmine dose is as follows:
60mg pyridostigmine is equivalent to 1 or 1.5mg subcutaneous neostigmine.
A suitable regimen for this individual could be 1mg neostigmine subcutaneous injection given four times a day.
Switching from neostigmine to pyridostigmine
There are no formal studies on switching from parenteral neostigmine to oral pyridostigmine. The switching advice below is based on established dosing equivalence referenced in standard medical literature.
Doses of 1 to 2.5mg are given subcutaneously or by intramuscular injection at suitable intervals throughout the day for myasthenia gravis.
The usual total daily dose is approximately 5 to 20mg neostigmine.
Using the equivalence factor, switch the parenteral neostigmine dose to oral pyridostigmine.
- 1 to 1.5mg intramuscular or subcutaneous neostigmine is equivalent to 60mg oral pyridostigmine.
Give oral pyridostigmine.
Repeat the dose at appropriate intervals throughout the day e.g. 3 to 4 hourly during the day and give a dose before going to bed.
A 60-year-old man uses 1.5mg subcutaneous neostigmine five times a day for myasthenia gravis. The prescriber would like to switch the individual to oral pyridostigmine. The method of calculating the oral pyridostigmine dose is as follows:
1 or 1.5mg subcutaneous neostigmine is equivalent to 60mg pyridostigmine.
A suitable regimen for this individual could be 60mg pyridostigmine given five times a day.
Monitoring after the switch
Monitor the individual closely after the switch to ensure the symptoms of myasthenia gravis are appropriately controlled and side effects are tolerable. Doses should be adjusted accordingly.
The healthcare professional initiating the switch should assess the individual and consider any additional monitoring on case-by-case basis.