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Enlon (edrophonium injection) ® is recommended for the differential diagnosis of myasthenia gravis and as an adjunct in the evaluation of treatment requirements in this disease. It may also be used for evaluating emergency treatment in myasthenic crises. Because of its brief duration of action, it is not recommended for maintenance therapy in myasthenia gravis.
Enlon (edrophonium injection) ® is also useful whenever a curare antagonist is needed to reverse the neuromuscular block produced by curare, tubocurarine, gallamine triethiodide or dimethyl-tubocurarine. It is not effective against decamethonium bromide and succinylcholine chloride. It may be used adjunctively in the treatment of respiratory depression caused by curare overdosage.
DOSAGE AND ADMINISTRATION
Enlon (edrophonium injection) ® Test in the Differential Diagnosis of Myasthenia Gravis:1-8
Intravenous Dosage (Adults): A tuberculin syringe containing 1 mL (10 mg) of Enlon (edrophonium injection) ® is prepared with an intravenous needle, and 0.2 mL (2 mg) is injected intravenously within 15 to 30 seconds. The needle is left in situ. Only if no reaction occurs after 45 seconds is the remaining 0.8 mL (8 mg) injected. If a cholinergic reaction (muscarinic side effects, skeletal muscle fasciculations and increased muscle weakness) occurs after injection of 0.2 mL (2 mg), the test is discontinued and atropine sulfate, 0.4 mg to 0.5 mg, is administered intravenously. After one-half hour the test may be repeated.
Intramuscular Dosage (Adults): In adults with inaccessible veins, dosage for intramuscular injection is 1 mL (10 mg) of Enlon (edrophonium injection) ®. Subjects who demonstrate hyperreactivity to this injection (cholinergic reaction), should be retested after one-half hour with 0.2 mL (2mg) of Enlon (edrophonium injection) ® intramuscularly to rule out false-negative reactions.
Dosage (Children): The intravenous testing dose of Enlon (edrophonium injection) ® in children weighing up to 75 lbs is 0.1 mL (1 mg); above this weight, the dose is 0.2 mL (2 mg). If there is no response after 45 seconds, it may be titrated up to 0.5 mL (5 mg) in children under 75 lbs, given in increments of 0.1 mL (1 mg) every 30 to 45 seconds and up to 1 mL (10 mg) in heavier children. In infants, the recommended dose is 0.05 mL (0.5 mg). Because of technical difficulty with intravenous injection in children, the intramuscular route may be used. In children weighing up to 75 lbs, 0.2 mL (2 mg) is injected intramuscularly, in children weighing more than 75 lbs, 0.5 mL (5 mg) is injected intramuscularly. All signs which would appear with the intravenous test appears with the intramuscular test except that there is a delay of two to ten minutes before a reaction is noted.
Enlon (edrophonium injection) ® Test for Evaluation of Treatment Requirements in Myasthenia Gravis: The recommended dose is 0.1 mL to 0.2 mL (1 mg to 2 mg) of Enlon (edrophonium injection) ®, administered intravenously one hour after oral intake of the drug being used in treatment. 1-5 Response will be myasthenic in the undertreated patient, adequate in the controlled patient, and cholinergic in the overtreated patient. Responses to Enlon (edrophonium injection) ® in myasthenic and nonmyasthenic individuals are summarized in the following chart.
|Muscle Strength (ptosis, diplopia dysphonia, dysphagia, dysarthria, respiration, Limb strength)||Increased||No change||Decreased|
|Fasciculations (orbicularis oculi, facial muscles, limb muscles)||Absent||Present or absent||Present or absent|
|Side reactions (lacrimation diaphoresis, salivation, abdominal cramps, nausea, vomiting, diarrhea)||Absent||Minimal.||Severe|
* Myasthenic Response- occurs in untreated myasthenics and may serve to establish diagnosis; in patients under treatment, indicates that therapy is inadequate.
Â Adequate Response- observed in treated patients when therapy is stabilized: a typical response in normal individuals. In addition to this response in non-myasthenics, the phenomenon of forced lid closure is often observed in psychoneurotics.
Â¡ Cholinergic Response- seen in myasthenics who have been overtreated with anticholinesterase drugs.
Enlon (edrophonium injection) ® Test in Crisis: The term crisis is applied to the myasthenic whenever severe respiratory distress with objective ventilatory inadequacy occurs and the response to medication is not predictable. This state may be secondary to a sudden increase in severity of myasthenia gravis (myasthenic crisis), or to overtreatment with anticholinesterase drugs (cholinergic crisis).
When a patient is apneic, controlled ventilation must be secured immediately in order to avoid cardiac arrest and irreversible central nervous system damage. No attempt is made to test with Enlon (edrophonium injection) ® until respiratory exchange is adequate.
Dosage used at this time is most important: If the patient is cholinergic, Enlon (edrophonium injection) ® will cause increased or opharyngeal secretions and further weakness in the muscles of respiration. If the crisis is myasthenic, the test clearly improves respiration and the patient can be treated with longer-acting intravenous anticholinesterase medication. When the test is performed, there should not be more than 0.2 mL (2 mg) Enlon (edrophonium injection) ® in the syringe. An intravenous dose of 0.1 mL (1 mg) is given initially. The patient†s heart action is carefully observed. If, after an interval of one minute, this dose does not further impair the patient, the remaining 0.1 mL (1 mg) can be injected. If no clear improvement of respiration occurs after 0.2 mL (2 mg) dose, it is usually wisest to discontinue all anticholinesterase drug therapy and secure controlled ventilation by tracheostomy with assisted respiration. 5
For Use as a Curare Antagonist: Enlon (edrophonium injection) ® should be administered by intravenous injection in 1 mL (10 mg) doses given slowly over a period of 30 to 45 seconds so that the onset of cholinergic reaction can be detected. This dosage may be repeated whenever necessary. The maximal dose for any one patient should be 4 mL (40 mg). Because of its brief effect, Enlon (edrophonium injection) ® should not be given prior to the administration of curare, tubocurarine, gallamine triethiodide or dimethyl-tubocurarine: it should be used at the time when its effect is needed. When given to counteract curare overdosage, the effect of each dose on the respiration should be carefully observed before it is repeated, and assisted ventilation should always be employed.
Parenteral drug products should be inspected visually for particulate matter and discoloration prior to administration, whenever solution and container permit.
ENLON (edrophonium injection) ® (edrophonium chloride injection, USP):
|NDC 10019-873-15||15 mL vials|
ENLON (edrophonium injection) ® (edrophonium chloride injection, USP) should be stored at controlled room temperature 15°-30°C (59°-86°F).
1. Osserman KE, Kaplan LI. JAMA 1952;150:265.
2. Osserman KE, Kaplan LI., Besson G. J Mt Sinai Hosp 1953;20:165.
3. Osserman KE, Kaplan LI. Arch Neurol Psychiatr 1953;70:385.
4. Osserman KE, Teng P. JAMA 1956;160:153.
5. Osserman KE, Genkins G. Ann Ny Acad Sci 1966;135:312.
6. Tether JE, Second International Symposium Proceedings, Myasthenia Gravis, 1961, p.444.
7. Tether JE, in HF Conn: Current Therapy 1960, Philadelphia, WB Saunders Go, p.551.
8. Tether JE, in HF Conn: Current Therapy 1965, Philadelphia, WB Saunders Co, p.556.
9. Grab D. Johns RJ. JAMA 1958;166:1855.This monograph has been modified to include the generic and brand name in many instances.
Last reviewed on RxList: 1/15/2005
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