Edrophonium Chloride
Edrophonium chloride
Also known as: Tensilon · Anticude · Camsilon · Reversol · Enlon-Plus · edrophonii chloridum
Reviewed by the VetSheet Veterinary TeamUpdated Apr 5, 2026Evidence-based veterinary reference
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Dosing by species
🌎 NA — North America🌍 EU — Europe
Dogs
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Presumptive diagnosis of myasthenia gravis (MG) | 0.1-0.2 mg/kg | IV | Once | — | 🌎 NA |
| Presumptive diagnosis of myasthenia gravis (MG) | 1-10 mg (total dose) | IV | Once | — | 🌎 NA |
| Presumptive diagnosis of myasthenia gravis (MG) | 0.1-0.2 mg/kg | IV | Once | — | 🌎 NA |
| Presumptive diagnosis of myasthenia gravis (MG) | 0.1 mg/kg | IV | Once | — | 🌎 NA |
- Presumptive diagnosis of myasthenia gravis (MG): Patient is gently exercised until fatigued. Place indwelling catheter. Have atropine drawn up (0.02-0.04 mg/kg IV) in case cholinergic signs develop. Flush catheter with sterile saline, then immediately lightly exercise or encourage to rise.
- Presumptive diagnosis of myasthenia gravis (MG): Presumptive positive test results in transient improvement in clinical weakness.
- Presumptive diagnosis of myasthenia gravis (MG): Have atropine and endotracheal tube readily available in case of overdose.
- Presumptive diagnosis of myasthenia gravis (MG): Pre-treat with atropine (0.02-0.04 mg/kg IM or SC). In affected animals, paresis should resolve within one minute and effects should last for up to 15 minutes.
Cats
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Presumptive diagnosis of myasthenia gravis (MG) | 0.25 to 0.5 mg (total dose) | IV | Once | — | 🌎 NA |
| Presumptive diagnosis of myasthenia gravis (MG) | 0.1 mg/kg | IV | Once | — | 🌎 NA |
- Presumptive diagnosis of myasthenia gravis (MG): Patient is gently exercised until fatigued. Place indwelling catheter. Have atropine drawn up (0.02-0.04 mg/kg IV) in case cholinergic signs develop. Flush catheter with sterile saline, then immediately lightly exercise or encourage to rise.
- Presumptive diagnosis of myasthenia gravis (MG): Pre-treat with atropine (0.02-0.04 mg/kg IM or SC). In affected animals, paresis should resolve within one minute and effects should last for up to 15 minutes.
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Overview
Edrophonium chloride is a short-acting, parenteral anticholinesterase agent primarily utilized in veterinary medicine for the presumptive diagnosis of myasthenia gravis (MG) via the 'Tensilon Test'.
While it can also be used to reverse non-depolarizing neuromuscular blocking agents or treat specific supraventricular tachycardias (SVTs), its extremely short duration of action often makes longer-acting alternatives (like neostigmine or pyridostigmine) more practical for these secondary indications.
Clinical Pearl: The 'Tensilon Test' has a fair percentage of false-positives and false-negatives. It is best used as a rapid, presumptive diagnostic tool while awaiting results from more specific and sensitive assays, such as the acetylcholine receptor (AChR) antibody test.
Mechanism of action
Edrophonium acts as a rapid, reversible inhibitor of the enzyme acetylcholinesterase.
Mechanism of Action: Edrophonium briefly attaches to acetylcholinesterase → inhibits its hydrolytic activity → acetylcholine accumulates in the synaptic cleft → prolonged and increased stimulation of nicotinic and muscarinic receptors.
In patients with myasthenia gravis, the sudden surge of acetylcholine temporarily overcomes the autoimmune blockade/destruction of nicotinic receptors at the neuromuscular junction, leading to a rapid (but transient) return of muscle strength. Systemically, acetylcholine accumulation also causes parasympathomimetic effects including miosis, increased intestinal muscle tone, bronchoconstriction, salivation, and bradycardia.
Safety & warnings
Contraindications
- Bronchial asthma
- Mechanical urinary tract obstruction
- Mechanical intestinal tract obstruction
- Known hypersensitivity to the drug
Adverse effects
- Urination
- Lacrimation
- Vomiting
- Defecation
- Bradycardia
- Bronchospasm
- Salivation
Precautions
Use with extreme caution in patients with bradycardias or atrioventricular block. Adequate monitoring and treatment must be available. Always have IV atropine and an endotracheal tube readily available before administering edrophonium. Safety during pregnancy is not established (FDA Category C); use only when clearly necessary.
Drug interactions
Antagonizes the muscarinic effects of edrophonium. Concurrent use should be done cautiously as atropine can mask the early clinical signs of a cholinergic crisis.
Theoretically may have additive cholinergic effects when used with edrophonium.
Edrophonium's cardiac effects may be increased; excessive slowing of heart rate (bradycardia) may occur.
Edrophonium may prolong the Phase I block of these agents.
Edrophonium antagonizes the neuromuscular blocking actions of these agents.
Monitoring
- Cholinergic adverse effects (heart rate, respiratory rate/effort, salivation)
- Improvement of paresis (for 1-15 minutes) for presumptive diagnosis of myasthenia gravis
Pharmacokinetics
Absorption
Only effective when given parenterally. After IV administration, effects on skeletal muscle begin within one minute.
Distribution
Not well described in veterinary literature.
Metabolism
Exact metabolic fate has not been well described.
Elimination
Excretion characteristics are not well described. Clinical effects generally persist for up to 10 minutes, though myasthenic patients may experience longer-lasting effects after the first dose.
Overdose
Overdosage of edrophonium may induce a cholinergic crisis.
Clinical Signs of Toxicity (SLUDGE syndrome and beyond):
- GI: Nausea, vomiting, diarrhea, salivation
- Respiratory: Increased bronchial secretions, bronchospasm, pulmonary edema, respiratory paralysis
- Ophthalmic: Miosis, blurred vision, lacrimation
- Cardiovascular: Bradycardia or tachycardia, cardiospasm, hypotension, cardiac arrest
- Musculoskeletal: Muscle cramps, profound weakness, sweating (in animals with sweat glands)
Treatment: Consists of immediate respiratory and cardiac supportive therapy. Administer atropine IV to counteract severe muscarinic effects.
Available products
Formulations
- Injection
Human-labeled
- Edrophonium Chloride Solution for Injection: 10 mg/mL in 10 mL & 15 mL vials (Enlon, Reversol)
- Edrophonium Chloride/Atropine Sulfate for Injection: 10 mg/mL with 0.14 mg/mL atropine sulfate in 5 mL single-dose amps & 15 mL multi-dose vials (Enlon-Plus)
Regulatory status
No regulatory data for: 🇺🇸 US · 🇪🇺 EU · 🇬🇧 UK · 🇭🇰 HK · 🇹🇼 TW · 🇯🇵 JP · 🇰🇷 KR · 🇦🇺 AU
Storage & stability
Store injection at room temperature. Physically compatible at Y-site injections with heparin sodium, hydrocortisone sodium succinate, potassium chloride, and vitamin B complex with C. Compatibility depends on pH, concentration, and temperature.
Client information
- Clinical Setting Only: Edrophonium is a specialized diagnostic drug that is only administered in a controlled veterinary hospital setting.
- Purpose: It is primarily used as a rapid, temporary test to help diagnose myasthenia gravis, a condition causing severe muscle weakness.
- What to Expect: Your veterinarian will closely monitor your pet during the test. Brief side effects such as drooling, vomiting, urination, or changes in heart rate can occur, but the veterinary team is prepared to treat these immediately if they arise.
VetSheet drug reference is intended for licensed veterinary professionals as a clinical decision-support aid, not a substitute for professional judgement or the manufacturer’s current label.