The Tensilon test uses the drug Tensilon (edrophonium) to help your doctor diagnose myasthenia gravis. Tensilon prevents the breakdown of the chemical acetylcholine, a neurotransmitter that nerve cells release to stimulate your muscles.
People with the chronic disease myasthenia gravis don’t have normal reactions to acetylcholine. Antibodies attack their acetylcholine receptors. This prevents muscles from being stimulated and makes muscles easy to tire.
A person tests positive for myasthenia gravis if their muscles get stronger after being injected with Tensilon.
Your doctor might order the Tensilon test if they suspect that you have myasthenia gravis. If you’ve already been diagnosed, they may also perform the test to monitor your dosage of Tensilon or another drug of a similar type, called an anticholinesterase. Anticholinesterase drugs work by preventing the breakdown of acetylcholine in people with myasthenia gravis.
Labored breathing and extremely weak muscles are symptoms that your myasthenia gravis has worsened or that you’ve overdosed on the medication. The Tensilon test helps your doctor determine the right treatment.
Before the test, your doctor might set dietary restrictions or tell you to discontinue your use of certain medications or supplements. Let your doctor know all of the medications you’re taking, including herbs. Some substances can interfere with your test results.
The test will start with an intravenous (IV) needle placed in your arm or the back of your hand. A small amount of Tensilon will then be injected. Your stomach might feel upset or your heart rate might increase from the drug. Depending on why the test is being administered, the rest of the procedure will continue in different ways.
For diagnosing myasthenia gravis
If your doctor suspects that you have myasthenia gravis, they’ll tell you to perform a repetitive movement to test your muscles. This movement may be:
- getting up and down from your chair
- crossing and uncrossing your legs
- holding your arms overhead until they get tired
- counting backward from 100 until your voice starts to weaken
Each time you get tired, they’ll give you another dose of Tensilon. You might get 3 or 4 shots of the drug. Your doctor will observe whether the shot revives your strength each time. If it does, you may be diagnosed with myasthenia gravis. Your doctor may also administer another anticholinesterase drug, called neostigmine (Prostigmin), to confirm the diagnosis.
For checking Tensilon overdose and disease progression
If your doctor is trying to determine whether you’ve overdosed on Tensilon or if your disease is getting worse, they’ll inject a small amount of Tensilon and see what happens. Depending on the results, you’ll be given an additional drug, either neostigmine or atropine (Atreza), to stabilize you.
Each of these procedures should take about 15 to 30 minutes.
Your doctor should be able to tell you the test results right away. You’ll likely be put on long-term anticholinesterase drug therapy if you’re diagnosed with myasthenia gravis. Your doctor might want you to undergo additional testing to confirm the diagnosis.
For determining whether you overdosed on medication or your condition has worsened, this test provides and immediate answer. If an injection of Tensilon temporarily boosts your strength, the myasthenia gravis has gotten worse and you’ll need further treatment. If the Tensilon injection makes you even weaker, then you might have too much anticholinesterase medication in your system.
Anticholinesterase medication is taken when necessary. There’s no fixed dosage. This is because the symptoms of myasthenia gravis can vary each day due to factors such as stress and weather. The varying dosage makes an unintentional overdose more likely. Reducing your dosage should solve the problem if you have minimal side effects.
Contact your doctor immediately if you have:
- noticeable muscular weakness
- difficulty swallowing
- respiratory problems
The Tensilon test has a number of common side effects. These usually last for less than a minute. Side effects include:
- upset stomach
- blurred vision
- increased saliva production
- dizziness or fainting
- breathing difficulties
- twitching or rapid, uncontrollable blinking
If you continue to feel unwell, the doctor may give you an injection of atropine. This drug reverses the effects of Tensilon.
In rare cases, the Tensilon test can have dangerous outcomes. These may include breathing failure or abnormal heart rhythms. That’s why the test is performed in places where emergency resuscitation equipment is available.
You might not be a good candidate for the test if you have:
- a slow heart rate
- an irregular heartbeat
- low blood pressure
- obstructions in the urinary tract or intestines
If you have sleep apnea, your doctor might not recommend the Tensilon test. This is a condition in which you temporarily stop breathing while sleeping.
Let your doctor know if you have any of these conditions. They’ll be able to determine the right treatment options for you.