PYRIDOSTIGMINE BROMIDE

PYRIDOSTIGMINE BROMIDE
(peer-id-oh-stig'meen)
Mestinon, Regonol
Classifications: anticholinergic agent; cholinesterase inhibitor;
Therapeutic: cholinesterase inhibitor

Prototype: Neostigmine
Pregnancy Category: C

Availability

60 mg/5 mL syrup; 60 mg tablet; 180 mg extended release tablet; 5 mg/mL injection

Action

Analog of neostigmine; indirect-acting cholinergic that inhibits cholinesterase activity. Facilitates transmission of impulses across myoneural junctions by blocking destruction of acetylcholine.

Therapeutic Effect

Direct stimulant action on voluntary muscle fibers and possibly on autonomic ganglia and CNS neurons. Produces increased tone in skeletal muscles.

Uses

Myasthenia gravis and as an antagonist to nondepolarizing skeletal muscle relaxants (e.g., curariform drugs).

Contraindications

Hypersensitivity to anticholinesterase agents or to bromides. Mechanical obstruction of urinary or intestinal tract; bradycardia, hypotension; pregnancy (category C).

Cautious Use

Bronchial asthma; epilepsy; renal impairment; vagotonia; hyperthyroidism; peptic ulcer; cardiac dysrhythmias.

Route & Dosage

Myasthenia Gravis
Adult: PO 60 mg–1.5 g/d spaced according to response of individual patient; sustained  release: 180–540 mg 1–2 times/d at intervals of at least 6 h IM/IV Approximately 1/30 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

Administration

Oral
  • Give with food or fluid.
  • Ensure that sustained release form is not chewed or crushed. Must be swallowed whole.
  • 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
  • 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.  

  • Store at 15°–30° C (59°–86° F). Protect from light and moisture.

Adverse Effects (≥1%)

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.

Interactions

Drug: Atropine nondepolarizing muscle relaxants antagonize effects of pyridostigmine.

Pharmacokinetics

Absorption: Poorly from GI tract. Onset: 30–45 min PO; 15 min IM; 2–5 min IV. Duration: 3–6 h. Distribution: Crosses placenta. Metabolism: In liver and in serum and tissue by cholinesterases. Elimination: In urine.

Nursing Implications

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.

Common adverse effects in italic, life-threatening effects underlined; generic names in bold; classifications in SMALL CAPS; Canadian drug name; Prototype drug

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