Enlon Dosage

Generic name: edrophonium chloride
Dosage form: injection, solution

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ENLON Test in the Differential Diagnosis of Myasthenia Gravis7-14

Intravenous Dosage (Adults)

A tuberculin syringe containing 1 mL (10 mg) of ENLON 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. Subjects who demonstrate hyperreactivity to this injection (cholinergic reaction), should be retested after one-half hour with 0.2 mL (2 mg) of ENLON intramuscularly to rule out false-negative reactions.

Dosage in Pediatric Patients

The intravenous testing dose of ENLON in pediatric patients 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 pediatric patients 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 patients. In infants, the recommended dose is 0.05 mL (0.5 mg). Because of technical difficulty with intravenous injection in pediatric patients, the intramuscular route may be used. In pediatric patients weighing up to 75 lbs, 0.2 mL (2 mg) is injected intramuscularly. In pediatric patients weighing more than 75 lbs, 0.5 mL (5 mg) is injected intramuscularly. All signs which would appear with the intravenous test appear with the intramuscular test except that there is a delay of 2 to 10 minutes before a reaction is noted.

ENLON 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, administered intravenously 1 hour after oral intake of the drug being used in treatment.7-11 Response will be myasthenic in the undertreated patient, adequate in the controlled patient, and cholinergic in the overtreated patient. Responses to ENLON in myasthenic and nonmyasthenic individuals are summarized in the following chart.8

*
Myasthenic Response - occurs in untreated myasthenics and may serve to establish diagnosis; in patients under treatment, indicates that therapy is inadequate.
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.
Cholinergic Response - seen in myasthenics who have been overtreated with anticholinesterase drugs.

Myasthenic*

Adequate

Cholinergic

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

ENLON 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 until respiratory exchange is adequate.

Dosage used at this time is most important

If the patient is cholinergic, ENLON will cause increased oropharyngeal 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 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 1 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 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 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.

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