Answer: Tensilon, or edrophonium, is an acetylcholinesterase inhibitor.
Our nervous system uses the chemical neurotransmitter acetylcholine for a variety of functions. In the peripheral nervous system, acetylcholine is used by motor neurons to cause muscle contraction, and is important for voluntary movement. Acetylcholine also helps regulate heart beat through release by the vagus nerve, under control of the parasympathetic nervous system. In the brain, acetylcholine is involved with processes such as memory and alertness.
After acetylcholine is released by a synapse it is cleared away by the action of a synaptic enzyme called acetylcholinesterase. This enzyme is one of the fastest acting enzymes in our body, and is capable of degrading tens of thousands of molecules each second.
Tensilon, or edrophonium, is a chemical that is capable of interfering with the action of acetylcholinesterase. Tensilon prevents the breakdown of acetylcholine, which results in an elevated level of acetylcholine at the synapse. Tensilon is a very short acting drug. Its effects last for tens of minutes.
Clinically, Tensilon is used to help doctors diagnose a rare muscle disorder called myasthenia gravis (MG). People with myasthenia gravis have profound muscle weakness that can result in difficulty with locomotion, double vision, and trouble speaking. MG is believed to result from autoimmune activity that causes the body to destroy the nicotinic acetylcholine receptors at the neuromuscular junction. When Tensilon is present, the inhibition of acetylcholinesterase increases synaptic concentration of acetylcholine, which can overcome the motor difficulties of myasthenia gravis.
Currently, Tensilon is not preferred as a diagnostic tool since it can produce false positives. The most accurate diagnostic tool we use is a blood test that detects autoantibodies for the anti-acetylcholine receptors or muscle specific tyrosine-kinase.