There is no direct conversion of oral pyridostigmine to parenteral neostigmine.

60mg pyridostigmine oral is approximately equivalent to 500 microgram neostigmine IV and 1-1.5 mg neostigmine IM or SC.

Patients who have their oral dose of pyridostigmine converted to a parenteral dose of neostigmine should be monitored closely to ensure that the neostigmine is adequately controlling their symptoms of myasthenia gravis and not causing untoward side effects.  Doses should be adjusted accordingly.