30 60 mg po every 4 6 hr initially with a maximum

i. 30-60 mg PO every 4-6 hr initially, with a
maximum daily dose of 360 mg
ii. Average daily dose: 600 mg/day
iii. Mild MG: 60-360 mg/day
iv. Severe MG: maximum daily dose as high as
1500 mg
d. Onset of effect is 30 minutes, duration 4 hr
e. Longer-acting preparation is available for
patients on stable dosing.

f. Monitor patient for cholinergic adverse
effects, such as nausea, vomiting, diarrhea,
increased salivation, bronchial secretions, and
cramps. These adverse effects can
be controlled with propantheline (15 mg may be
given 15-30 minutes prior to administration of
pyridostigmine).
2. Drugs to try to avoid in patients with MG
include:
a. Ketolides
b. Aminoglycosides
c. Polypeptides (when not used topically)
d. Glycopeptides
e. Lincosamide
f. Class 1 antiarrhythmics
E. Immunomodulating therapy: necessary for
patients with MG and may require lifelong
therapy (IVIG and plasmapheresis for rapid
immunomodulating therapies, see myasthenic
crisis)
1. Prednisone
a. Should be administered to those who have
responded poorly to anticholinesterase drugs
and, if indicated, have already undergone
thymectomy
b. Dose is determined on an individual basis
c. High initial dose can gradually be tapered to
a lower maintenance dose
d. Continue to taper very slowly, attempting to
establish the minimum dosage necessary to
maintain remission
2. Azathioprine
a. Widely used as a nonsteroidal
immunosuppressant and can be used as
monotherapy
b. Dose is started at 50 mg/day, titrated up to
2-3 mg/kg PO per day if well tolerated
c. May cause macrocytosis and lymphopenia
(drug should not be discontinued for this effect)
d. If remission not achieved, refer to specialist
for other immune modulating therapies (e.g.,
methotrexate, cyclosporin, mycophenolate, or
tacrolimus)
E. Management of impending myasthenic crisis
1. Airway and ventilatory management
a. Patients with bulbar weakness, declining vital
capacity (less than 20 ml/kg), maximal
inspiratory force of negative 30 cm H2O, or
weak or ineffective cough that increases work
of breathing, should be admitted to an intensive
care unit to monitor for possible intubation and
mechanical ventilation.
b. Vital capacity may not be reliable in patients
having difficulty maintaining a seal around a
spirometer mouthpiece.
2. Rapid immunomodulating therapies (IVIG and
plasmapheresis are equivocal in efficacy in
myasthenic crisis)
a. IVIG
i. Therapy that has been used traditionally as
an alternative to plasmapheresis
ii. Dosing: 1 gram/kg/day IV for 2 days or 400
mg/kg/day IV for 5 days, for a total of 1-2
grams/kg IV for 2-5 days
iii. Major component is IgG molecule and is
derived from healthy donated blood neutralizing
pathogenic antibodies and limiting activation of
the complement system
iv. Decision to use over plasmapheresis usually
determined by available resources and
comorbidities increasing potential
complications, such as heart disease, renal
insufficiency, and IgA deficiency
b. Plasmapheresis
i. Mechanically removes antibodies and
activated complements from the blood
ii. Routine frequency is five times