Antilirium


physostigmine

(fi-zoe-stig-meen) physostigmine,

Antilirium

(trade name)

Classification

Therapeutic: antidotes
Pharmacologic: cholinergics
Pregnancy Category: C
See for ophthalmic use

Indications

Reversal of CNS effects due to overdose of drugs capable of causing the anticholinergic syndrome, including:
  • belladonna or other plant alkaloids,
  • phenothiazines,
  • tricyclic antidepressants,
  • antihistamines (reverses delirium, hallucinations, coma, and some arrhythmias, but not completely effective in reversing cardiac conduction defects or tachycardia).

Action

Inhibits the breakdown of acetylcholine so that it accumulates and has a prolonged effect. Result is generalized cholinergic response, including:
  • Miosis,
  • Increased tone of intestinal and skeletal musculature,
  • Bronchial and ureteral constriction,
  • Bradycardia,
  • Increased salivation,
  • Lacrimation,
  • Sweating,
  • CNS stimulation.

Therapeutic effects

Reversal of anticholinergic excess.

Pharmacokinetics

Absorption: Readily absorbed from subcut and IM sites.Distribution: Widely distributed; crosses the blood-brain barrier.Metabolism and Excretion: Metabolized by cholinesterases present in many tissues. Small amounts excreted unchanged in the urine.Half-life: 1–2 hours.

Time/action profile (systemic cholinergic effects = miosis)

ROUTEONSETPEAKDURATION
IM, IV3–8 minunknown45–60 min†
†May be up to 5 hr

Contraindications/Precautions

Contraindicated in: Hypersensitivity; Hypersensitivity to bisulfites; Gangrene; Asthma; Diabetes; Cardiovascular disease; Mechanical obstruction of the GI or GU tract; Any vagotonic state; Concurrent use of choline esters or depolarizing neuromuscular blocking agents (decamethonium, succinylcholine); Lactation: Discontinue medication or bottle feed.; Pediatric: Preparations containing benzyl alcohol should be avoided in newborns to prevent potentially fatal gasping syndrome.Use Cautiously in: Ulcer disease; Epilepsy; Hyperthyroidism.Exercise Extreme Caution in: Pregnancy or lactation (10–20% of newborns will suffer from muscle weakness; use only if clearly indicated); Children (reserve for life-threatening situations).

Adverse Reactions/Side Effects

Central nervous system

  • seizures (life-threatening)
  • restlessness (most frequent)
  • dizziness
  • hallucinations
  • weakness

Ear, Eye, Nose, Throat

  • lacrimation
  • miosis

Respiratory

  • bronchospasm (most frequent)
  • excess respiratory secretions

Cardiovascular

  • bradycardia (most frequent)
  • hypotension

Gastrointestinal

  • abdominal cramps (most frequent)
  • diarrhea (most frequent)
  • nausea (most frequent)
  • vomiting (most frequent)
  • excess salivation

Dermatologic

  • rash

Interactions

Drug-Drug interaction

Prolongs action of depolarizing muscle-relaxing agents (succinylcholine,decamethonium ); avoid concurrent use.Cholinergic effects may be antagonized by other drugs possessing anticholinergic properties, includingantihistamines, antidepressants, atropine, haloperidol,phenothiazines, quinidine, and disopyramide.Angel's trumpet, jimson weed, and scopolia may antagonize cholinergic effects.

Route/Dosage

Intramuscular Intravenous (Adults) Anticholinergic toxicity—2 mg initially; may be repeated as symptoms recur. Postanesthesia—0.5–1 mg; may be repeated q 10–30 min.Intramuscular Intravenous (Children) 20 mcg/kg; may repeat every 5–10 min as needed (up to 2 mg total dose).

Availability (generic available)

Injection: 1 mg/mL in 2-mL ampules and 1-mL prefilled syringes

Nursing implications

Nursing assessment

  • Monitor pulse, respiratory rate, and BP frequently throughout parenteral administration. Monitor ECG during IV administration.
  • Anticholinergic Excess: Monitor neurologic status frequently. Institute seizure precautions Protect patient from self-injury that may be caused by CNS effects of overdose.
    • Overdose is manifested by bradycardia, respiratory distress, seizures, weakness, nausea, vomiting, stomach cramps, diarrhea, diaphoresis, and increased salivation and tearing.
    • Atropine is the antidote.
    • Treatment of overdose includes establishing an airway and supporting ventilation, atropine sulfate 2–4 mg (may be repeated every 3–10 min to control muscarinic effects), pralidoxime chloride 50–100 mg/min (to control neurologic and skeletal muscle effects), and supportive therapy.

Potential Nursing Diagnoses

Risk for injury (Indications)

Implementation

  • Intravenous Administration
  • Repeated doses may be needed because of short duration of action.
  • Rate: May be given through Y-site at a rate of no more than 1 mg over 1 min (0.5 mg over 1 min for children). Rapid administration may cause bradycardia; increased salivation, which can lead to respiratory distress; or seizures.

Patient/Family Teaching

  • Anticholinergic Excess: Explain purpose of medication and need for close monitoring.

Evaluation/Desired Outcomes

  • Reversal of CNS symptoms secondary to anticholinergic excess resulting from drug overdose or ingestion of poisonous plants.