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i. 30-60 mg PO every 4-6 hr initially, with a maximum daily dose of 360 mgii. Average daily dose: 600 mg/dayiii. Mild MG: 60-360 mg/dayiv. Severe MG: maximum daily dose as high as 1500 mgd. Onset of effect is 30 minutes, duration 4 hre. 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 begiven 15-30 minutes prior to administration of pyridostigmine).2. Drugs to try to avoid in patients with MG include:a. Ketolidesb. Aminoglycosidesc. Polypeptides (when not used topically)d. Glycopeptidese. Lincosamidef. Class 1 antiarrhythmicsE. Immunomodulating therapy: necessary for patients with MG and may require lifelong therapy (IVIG and plasmapheresis for rapid immunomodulating therapies, see myasthenic crisis)1. Prednisonea. Should be administered to those who have responded poorly to anticholinesterase drugs and, if indicated, have already undergone thymectomyb. Dose is determined on an individual basisc. High initial dose can gradually be tapered to a lower maintenance dosed. Continue to taper very slowly, attempting to establish the minimum dosage necessary to maintain remission2. Azathioprinea. Widely used as a nonsteroidal immunosuppressant and can be used as monotherapyb. Dose is started at 50 mg/day, titrated up to 2-3 mg/kg PO per day if well toleratedc. 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 crisis1. Airway and ventilatory managementa. Patients with bulbar weakness, declining vitalcapacity (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 intensivecare 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 andplasmapheresis are equivocal in efficacy in myasthenic crisis)a. IVIGi. Therapy that has been used traditionally as an alternative to plasmapheresisii. 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 daysiii. Major component is IgG molecule and is derived from healthy donated blood neutralizingpathogenic antibodies and limiting activation of the complement systemiv. Decision to use over plasmapheresis usually determined by available resources and comorbidities increasing potential complications, such as heart disease, renal insufficiency, and IgA deficiencyb. Plasmapheresisi. Mechanically removes antibodies and activated complements from the bloodii. Routine frequency is five times