Enlon, Tensilon
Classifications: cholinergic agent; cholinesterase inhibitor;
Therapeutic: cholinesterase inhibitor

Prototype: Neostigmine
Pregnancy Category: C


10 mg/mL injection


Indirect-acting cholinesterase inhibitor that acts as antidote to curariform drugs by displacing them from muscle cell receptor sites, thus permitting resumption of normal transmission of neuromuscular impulses.

Therapeutic Effect

Acts as antidote to curariform drugs by displacing them from muscle cell receptor sites, thus permitting resumption of normal transmission of neuromuscular impulses.


Differential diagnosis and as adjunct in evaluation of treatment requirements of myasthenia gravis. Not recommended for maintenance therapy in myasthenia gravis because of its short duration of action.

Unlabeled Uses

To terminate paroxysmal atrial tachycardia, as an aid in diagnosing supraventricular tachyarrhythmias, and to evaluate function of demand pacemakers.


Hypersensitivity to anticholinesterase agents; cholinesterase inhibitor toxicity; intestinal and urinary obstruction; pregnancy (category C), lactation.

Cautious Use

Sulfite hypersensitivity; bronchial asthma; cardiac arrhythmias; bradycardia; peptic ulcer disease; hypotension; patients receiving digitalis.

Route & Dosage

Myasthenia Gravis Diagnosis
Adult: IV Prepare 10 mg in a syringe; inject 2 mg over 15–30 sec, if no reaction after 45 sec, inject the remaining 8 mg, may repeat test after 30 min IM Inject 10 mg, if cholinergic reaction occurs, retest after 30 min with 2 mg to rule out false-negative reaction
Child: IV ≤34 kg, 1 mg, if no response after 45 sec, dose may be titrated up to 5 mg IM 2 mg IV >34 kg, 2 mg, if no response after 45 sec, dose may be titrated up to 10 mg IM 5 mg
Infant: IM 0.5–1 mg

Evaluation of Myasthenia Treatment
Adult: IV 1–2 mg administered 1 h after last PO dose of anticholinesterase medication


  • Note: Have antidote (atropine sulfate) immediately available and facilities for endotracheal intubation, tracheostomy, suction, assisted respiration, and cardiac monitoring for treatment of cholinergic reaction.

PREPARE: Direct/Infusion: May be given undiluted or diluted in D5W or NS for infusion.  

ADMINISTER: Direct: Inject 2 mg (adult & child >34 kg) or 1 mg (child ≤34 kg) over 15–30 sec; if no reaction after 45 sec, inject additional 8 mg (adult) or titrate up to a total of 8 mg additional (child >34 kg) or titrate in 1 mg increments up to a total of 4 mg additional (child ≤34 kg), may repeat test after 30 min. If cholinergic reaction (increased muscle weakness) is obtained after initial 1 or 2 mg, discontinue test and give atropine IV (as ordered).  IV Infusion: Infuse over 1 h.  

  • Note: Some clinicians recommend giving a 1–2 mg test dose of edrophonium to older adult patients, to those with history of heart disease or who take digitalis, and possibly to all patients.

Adverse Effects (≥1%)

Body as a Whole: Severe adverse effects uncommon with usual doses. CNS: Weakness, muscle cramps, dysphoria, fasciculations, incoordination, dysarthria, dysphagia, convulsions, respiratory paralysis. CV: Bradycardia, irregular pulse, hypotension, pulmonary edema. Special Senses: Miosis, blurred vision, diplopia, lacrimation. GI: Diarrhea, abdominal cramps, nausea, vomiting, excessive salivation. Respiratory: Increased bronchial secretions, bronchospasm, laryngospasm, pulmonary edema. Other: Excessive sweating, urinary frequency, incontinence.


Drug: Procainamide, quinidine may antagonize the effects of edrophonium; digitalis glycosides increase the sensitivity of the heart to edrophonium; succinylcholine, decamethonium may prolong neuromuscular blockade.


Onset: 30–60 sec IV; 2–10 min IM. Duration: 5–10 min IV; 5–30 min IM.

Nursing Implications

Assessment & Drug Effects

  • Monitor vital signs. Observe for signs of respiratory distress. Patients >50 y are particularly likely to develop bradycardia, hypotension, and cardiac arrest.
  • Edrophonium test for myasthenia gravis: All cholinesterase inhibitors (anticholinesterases) should be discontinued for at least 8 h before test. Positive response to edrophonium test consists of brief improvement in muscle strength unaccompanied by lingual or skeletal muscle fasciculations.
  • Evaluation of myasthenic treatment: Myasthenic response (immediate subjective improvement with increased muscle strength, absence of fasciculations; generally indicates that patient requires larger dose of anticholinesterase agent or longer-acting drug); Cholinergic response [muscarinic adverse effects (lacrimation, diaphoresis, salivation, abdominal cramps, diarrhea, nausea, vomiting; accompanied by decrease in muscle strength; usually indicates over-treatment with cholinesterase inhibitor)]; Adequate response [no change in muscle strength; fasciculations may be present or absent; minimal cholinergic adverse effects (observed in patients at or near optimal dosage level)].

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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