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edrophonium chloride injection
ENLON (edrophonium chloride injection, USP)
|Eye:||Increased lacrimation, pupillary constriction, spasm of accommodation, diplopia, conjunctival hyperemia.|
|CNS:||Convulsions, dysarthria, dysphonia, dysphagia.|
|Respiratory:||Increased tracheobronchial secretions, laryngospasm, bronchiolar constriction, paralysis of muscles of respiration, central respiratory paralysis.|
|Cardiac:||Arrhythmias (especially bradycardia), fall in cardiac output leading to hypotension.|
|G.I.:||Increased salivary, gastric and intestinal secretion, nausea, vomiting, increased peristalsis, diarrhea, abdominal cramps.|
|Skeletal Muscle:||Weakness, fasciculations.|
|Miscellaneous:||Increased urinary frequency and incontinence, diaphoresis.|
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.
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.
The intravenous testing dose of ENLON 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.
The recommended dose is 0.1 mL to 0.2 mL (1 mg to 2 mg) of ENLON, 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 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|
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 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
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.
Care should be given when administering this drug to patients with symptoms of myasthenic weakness who are also on anticholinesterase drugs. Since symptoms of anticholinesterase overdose (cholinergic crisis) may mimic underdosage (myasthenic weakness), their condition may be worsened by the use of this drug. (See OVERDOSAGE section for treatment.)
With drugs of this type, muscarine-like symptoms (nausea, vomiting, diarrhea, sweating, increased bronchial and salivary secretions and bradycardia) often appear with overdosage (cholinergic crisis). An important complication that can arise is obstruction of the airway by bronchial secretions. These may be managed with suction (especially if tracheostomy has been performed) and by the use of atropine. Many experts have advocated a wide range of dosages of atropine (for ENLON, see atropine dosage below), but if there are copious secretions, up to 1.2 mg intravenously may be given initially and repeated every 20 minutes until secretions are controlled. Signs of atropine overdosage such as dry mouth, flush and tachycardia should be avoided as tenacious secretions and bronchial plugs may form. A total dose of atropine of 5 to 10 mg or even more may be required. The following steps should be taken in the management of overdosage of ENLON:
|NDC 10019-873-15||15 mL vials|
edrophonium chloride injection
Revised: 10/2006 Baxter Healthcare Corporation
Reproduced with permission of U.S. National Library of Medicine
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