From the Guidelines
The Edrophonium (Tensilon) test is primarily indicated for diagnosing myasthenia gravis, particularly in cases where the diagnosis is uncertain based on clinical presentation and other tests. This is supported by the 2020 study on adult strabismus preferred practice pattern, which notes that Tensilon testing may be considered for diagnosis, especially when performed by an experienced practitioner in a monitored setting 1. The test is useful for confirming the diagnosis of myasthenia gravis, especially when other tests such as antiacetylcholine receptor antibody tests are negative.
Some key points to consider when using the Edrophonium (Tensilon) test include:
- It is 95% sensitive for generalized myasthenia and 86% sensitive in cases of ocular myasthenia 1
- The test should be performed in a monitored setting with atropine available for potential administration to counteract muscarinic activity 1
- The test works by temporarily increasing acetylcholine levels at the neuromuscular junction, which can improve muscle strength in patients with myasthenia gravis
- Other diagnostic tests such as repetitive nerve stimulation testing and single fiber electromyography may also be used to assist in diagnosis, with single fiber EMG considered the gold standard in many centers 1
It is essential to note that the Edrophonium (Tensilon) test should only be performed by a practitioner experienced in its administration, due to the potential for muscarinic side effects such as excess tearing, salivation, sweating, abdominal cramping, bradycardia, bronchospasm, hypotension, and syncope 1.
From the FDA Drug Label
The 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 one hour after oral intake of the drug being used in treatment. Responses to ENLON in myasthenic and nonmyasthenic individuals are summarized in the following chart
- Myasthenic Response- occurs in untreated myasthenics and may serve to establish diagnosis; in patients under treatment, indicates that therapy is inadequate. The Erdophonin Tensilon test indication is for the diagnosis and evaluation of treatment requirements in Myasthenia Gravis 2.
- The test can help establish a diagnosis of myasthenia gravis in untreated patients.
- In patients under treatment, it can indicate if therapy is inadequate.
- The test can also help differentiate between myasthenic crisis and cholinergic crisis in patients with severe respiratory distress.
From the Research
Erdophonin Tensilon Test Indication
The Erdophonin Tensilon test is used to diagnose disorders of neuromuscular transmission, particularly myasthenia gravis (MG) and Lambert-Eaton myasthenic syndrome (LEMS). The test involves administering edrophonium (Tensilon) to the patient and observing for an improvement in muscle strength.
Key Indications
- Myasthenia gravis (MG) diagnosis: The Tensilon test can help confirm the diagnosis of MG, especially in patients with fluctuating weakness and other symptoms suggestive of the disease 3, 4, 5.
- Lambert-Eaton myasthenic syndrome (LEMS) diagnosis: Although the Tensilon test is not as commonly used for LEMS diagnosis, it can still be helpful in certain cases, particularly when combined with other diagnostic tests 4, 5, 6.
- Differential diagnosis: The Tensilon test can help differentiate between MG and other disorders that may present with similar symptoms, such as end-stage renal disease 3.
Important Considerations
- Interpretation of results: A positive response to the Tensilon test must be interpreted with caution, especially in patients with end-stage renal disease, as the test results may be influenced by metabolic abnormalities and other factors 3.
- Combination with other tests: The Tensilon test is often used in combination with other diagnostic tests, such as antibody tests and electromyography, to confirm the diagnosis of MG or LEMS 4, 5, 6, 7.