Spinal muscular atrophy (SMA) is an inherited neurodegenerative disorder characterized by progressive muscle weakness and atrophy.

One symptom of SMA is drooling, which is caused by jaw spasms, excessive saliva production, and difficulty in swallowing.

Certain medications may help decrease drooling in SMA patients. These include Botox (onabotulinumtoxinA), amitriptyline (formerly marketed under the brand name Elavil in the U.S. where generic versions are still available), Robinul (glycopyrrolate), and AtroPen (atropine). They all function by inhibiting the cholinergic system.

What is the cholinergic system?

The cholinergic system is a part of the nervous system that uses the neurotransmitter or chemical messenger called acetylcholine to transmit nerve signals. Neurotransmitters are released by nerve cells as a result of an incoming stimulus from the brain or another nerve cell. Once released, they bind to receptors found on the surface of a nearby cell. This can be another nerve cell, a muscle cell, or a gland cell. When neurotransmitters bind to muscle cells, they may trigger muscle contraction. When they bind to gland cells, they may cause secretion of fluids.

Botox

Botox is a neurotoxic protein that is obtained from the bacterium Clostridium botulinum. It inhibits the release of acetylcholine. When injected into the jaw or salivary glands, Botox can reduce jaw spasms and the secretion of saliva and, subsequently, drooling.

Amitriptyline

Amitriptyline is a medication for the treatment of depression, pain, and migraines. It acts through a number of different mechanisms. When taken orally, it blocks acetylcholine receptors in the glands that secrete saliva and thereby reduces drooling.

Robinul

Robinul is an anti-spasmodic or agent that suppresses muscle spasms. It is also used to reduce secretions from the salivary glands, pharynx (part of the throat), trachea (windpipe), and bronchi (air tubes that lead to the lungs).

Robinul also acts as an anticholinergic. In SMA patients, it is injected into salivary glands and reduces drooling.

AtroPen

AtroPen is a medication that is used to treat nerve agent poisoning, decrease saliva production, and reduce muscle spasms of the gastrointestinal tract as well as urinary and gallbladder systems.

When injected into salivary glands, AtroPen blocks the action of acetylcholine by binding to its receptors on the glands and reduces drooling.

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