edrophonium

General

Pronunciation
e-droh-FONE-ee-yum [Pronunciation]

Trade Name(s)

• Enlon

• Tensilon

Pregnancy Category
Category C

Ther. class.
antidotes

Pharm. class.
anticholinesterases
cholinergics

Indications

• Diagnosis of myasthenia gravis.

• Assessment of adequacy of anticholinesterase therapy in myasthenia gravis.

• Differentiating myasthenic from cholinergic crisis.

• Reversal of muscle paralysis from nondepolarizing neuromuscular blocking agents.

Action

Inhibits the breakdown of acetylcholine so that it accumulates and has a prolonged effect. Effects include miosis; increased intestinal and skeletal muscle tone; bronchial constriction; bradycardia; increased salivation, lacrimation, and sweating.

Therapeutic Effect(s):

• Short-lived improvement in muscular function in patients with myasthenia gravis.

• Reversal of nondepolarizing neuromuscular blocking agents.

Pharmacokinetics

Absorption: Absorption following IM and subcut administration not known.

Distribution: 1.1 L/kg.

Metabolism and Excretion: Unknown.

Half-life: 73–126 min.

TIME/ACTION PROFILE (cholinergic activity)

ROUTE	ONSET	PEAK	DURATION
IM	2–10 min	unknown	5–30 min
IV	30–60 sec	unknown	10 min

Contraindication/Precautions

Contraindicated in:

• Hypersensitivity;

• Mechanical obstruction of the GI or GU tract;

• Hypersensitivity to bisulfites;

• OB: May cause uterine irritability after IV administration near term; newborns may display muscle weakness;

• Lactation: Lactation.

Use Cautiously in:

• History of asthma;

• Cardiovascular disease;

• Because some patients may be extremely sensitive to the effects of anticholinesterases, atropine should be available in case of excessive dosage.

Adverse Reactions/Side Effects

CNS: SEIZURES, dizziness , dysphasia, dysphonia, weakness.

EENT: diplopia, lacrimation, miosis.

Resp: bronchospasm, excess secretions.

CV: bradycardia, hypotension.

GI: abdominal cramps, diarrhea, dysphagia, excess salivation, vomiting, nausea.

GU: incontinence, urinary frequency.

Derm: sweating, rashes.

MS: fasciculation.

*CAPITALS indicates life-threatening.
*italic indicates most frequent.

Interactions

Drug-Drug

• Action may be antagonized by drugs possessing anticholinergic properties , including antihistamines , antidepressants , atropine , haloperidol , phenothiazines , quinidine , and disopyramide .

• Prolongs action of depolarizing muscle-relaxing agents ( succinylcholine , decamethonium ).

• May lead to ↑ bradycardia in patients receiving digoxin .

Drug-Natural Products
Angel's trumpet , jimson weed , and scopolia may antagonize cholinergic effects.

Route/Dosage

Diagnosis of Myasthenia Gravis

• IV (Adults): 2 mg; if no response, administer an additional 8 mg after 45 sec; may repeat test in 30 min. If cholinergic response occurs after initial 2 mg dose, administer atropine 0.4–0.5 mg IV. Patients >50 yr should be pretreated with atropine to prevent bradycardia/hypotension..

• IV (Children >34 kg): 2 mg; if no response after 45 sec, may administer 1 mg every 30–45 sec to a total of 10 mg..

• IV (Children <34 kg): 1 mg; if no response after 45 sec, may administer 1 mg every 45 sec to a total of 5 mg..

• IV (Infants): 0.5 mg..

• IM (Adults): 10 mg. If cholinergic response occurs, may repeat 2-mg dose in 30 min to rule out false-negative reaction. Patients >50 yr should be pretreated with atropine to prevent bradycardia/hypotension..

• IM (Children >34 kg): 5 mg..

• IM (Children <34 kg): 2 mg..

Assessment of Anticholinesterase Therapy

• IV (Adults): 1–2 mg 1 hr after oral anticholinesterase dose..

Differentiation of Cholinergic from Myasthenic Crisis

• IV (Adults): 1 mg; may give additional 1 mg 1 min later..

Reversal of Nondepolarizing Neuromuscular Blocking Agents

• IV (Adults): 10 mg; may repeat as needed (not to exceed 40 mg). Doses of 0.5–1 mg/kg have been used..

Availability

• Injection: 10 mg/mL

• In combination with: atropine (Enlon-Plus). (See combination drugs).

Assessment

• Assess neuromuscular status (ptosis, diplopia, vital capacity, ability to swallow, extremity strength) prior to and immediately after administration.

» Reversal of nondepolarizing neuromuscular blocking agents is more rapid in pediatric patients.

» To differentiate myasthenic from cholinergic crisis, assess for increased weakness, diaphoresis, increased saliva and bronchial secretions, dyspnea, nausea, vomiting, diarrhea, and bradycardia. If these symptoms occur after administration of edrophonium, patient is in cholinergic crisis. If strength improves after administration of edrophonium, patient is in myasthenic crisis.

Toxicity and Overdose

• Atropine may be used for treatment of cholinergic symptoms. Oxygen and resuscitation equipment should be available.

Potential Nursing Diagnoses

• Ineffective breathing pattern (Indications)

Implementation

For myasthenia gravis patients, diagnostic IV dose and dose to differentiate myasthenic from cholinergic crisis should be administered by a physician.

IV Adminstration:

• Direct IV:

Diluent: Administer undiluted with a tuberculin syringe.
Concentration: 10 mg/mL.

• Rate:
Administer doses over 30–45 sec.

• Y-Site Compatibility:

» heparin

» hydrocortisone

» potassium chloride

» vitamin B complex with C