Final answer:
Riluzole is the FDA-approved drug used to treat ALS by reducing excitatory neurotransmission and glutamate release, potentially slowing disease progression.
Step-by-step explanation:
The drug used to treat Amyotrophic lateral sclerosis (ALS) is Riluzole (Rilutek), which is the only therapeutic approved by the United States Food and Drug Administration for ALS treatment. Riluzole acts by reducing excitatory neurotransmission, hence decreasing glutamate release from neurons, which might help in slowing the progression of the disease. ALS is characterized by selective motor neuron degeneration, possibly due to excitotoxicity mediated by excess glutamatergic input and the presence of calcium-permeable AMPA receptors. This excitotoxicity can potentially be mitigated by therapeutic measures such as Riluzole, which leads to a slight extension in survival, although not a cure for ALS.