PYRIDOSTIGMINE BROMIDE
(peer-id-oh-stig'meen)
Mestinon
Classifications: autonomic nervous system agent; cholinergic (parasympathomimetic); cholinesterase inhibitor
Prototype: Neostigmine
Pregnancy Category: C
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60 mg/5 mL syrup; 60 mg tablet; 180 mg extended-release tablet 5 mg/mL injection
Analog of neostigmine; indirect-acting cholinergic that inhibits cholinesterase activity. Drug facilitates transmission of
impulses across myoneural junctions by blocking destruction of acetylcholine. Has fewer adverse effects and longer duration
of action than neostigmine.
Direct stimulant action on voluntary muscle fibers and possibly on autonomic ganglia and CNS neurons. Produces increased tone
in skeletal muscles.
Myasthenia gravis and as an antagonist to nondepolarizing skeletal muscle relaxants (e.g., curariform drugs).
Hypersensitivity to anticholinesterase agents or to bromides. Mechanical obstruction of urinary or intestinal tract; bradycardia,
hypotension; pregnancy (category C), and lactation.
Bronchial asthma; epilepsy; vagotonia; hyperthyroidism; peptic ulcer; cardiac dysrhythmias.
Myasthenia Gravis
Adult: PO 60 mg–1.5 g/d spaced according to requirements and response of individual patient; sustained release: 180–540 mg 1–2 times/d at intervals of at least 6 h IM/IV Approximately 1/30th of PO dose
Child: PO 7 mg/kg/d divided into 5–6 doses
Neonates: PO 5 mg q4–6h IM/IV 0.05–0.15 mg/kg q4–6h
Reversal of Muscle Relaxants
Adult: IV 10–20 mg immediately preceded by IV atropine
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Oral
- Give with food or fluid.
- Ensure that sustained release form is not chewed or crushed. Must be swallowed whole.
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Note: A syrup is available. Some patients may not like it because it is sweet; try to make it more palatable by giving it over ice
chips. The syrup formulation contains 5% alcohol.
Intramuscular
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Note: Parenteral dose is about 1/30 the oral adult dose.
- Give deep IM into a large muscle.
| Intravenous PREPARE: Direct: Give undiluted. Do NOT add to IV solutions.
ADMINISTER: Direct: Give at a rate of 0.5 mg over 1 min for myasthenia gravis; 5 mg over 1 min for reversal of muscle relaxants.
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- Store at 15°–30° C (59°–86° F). Protect from light and moisture.
Skin: Acneiform rash. Hematologic: Thrombophlebitis (following IV administration). GI:
Nausea, vomiting, diarrhea.
Special Senses:
Miosis.
Body as a Whole:
Excessive salivation and sweating, weakness, fasciculation. Respiratory: Increased bronchial secretion, bronchoconstriction. CV: Bradycardia, hypotension.
Drug:
Atropine
nondepolarizing muscle relaxants antagonize effects of pyridostigmine.
Absorption: Poorly absorbed from GI tract. Onset: 30–45 min PO; 15 min IM; 2–5 min IV. Duration: 3–6 h. Distribution: Crosses placenta. Metabolism: Metabolized in liver and in serum and tissue by cholinesterases. Elimination: Excreted in urine.
Assessment & Drug Effects
- Report increasing muscular weakness, cramps, or fasciculations. Failure of patient to show improvement may reflect either
underdosage or overdosage.
- Observe patient closely if atropine is used to abolish GI adverse effects or other muscarinic adverse effects because it may
mask signs of overdosage (cholinergic crisis): Increasing muscle weakness, which through involvement of respiratory muscles
can lead to death.
- Monitor vital signs frequently, especially respiratory rate.
- Observe for signs of cholinergic reactions (see Appendix F), particularly when drug is administered IV.
- Observe neonates of myasthenic mothers, who have received pyridostigmine, closely for difficulty in breathing, swallowing,
or sucking.
- Observe patient continuously when used as muscle relaxant antagonist. Airway and respiratory assistance must be maintained
until full recovery of voluntary respiration and neuromuscular transmission is assured. Complete recovery usually occurs within
30 min.
Patient & Family Education
- Be aware that duration of drug action may vary with physical and emotional stress, as well as with severity of disease.
- Report onset of rash to physician. Drug may be discontinued.
- Sustained release tablets may become mottled in appearance; this does not affect their potency.
- Do not breast feed while taking this drug without consulting physician.
1%)
Canadian drug name; 
Prototype drug