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 swallowing.

Certain medications may help decrease drooling in SMA patients. These include Botox (onabotulinumtoxinA), Elavil (amitriptyline), 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 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 it can reduce jaw spasms and the secretion of saliva and, subsequently, drooling.


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


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

Robinul’s action also is anticholinergic. In SMA patients, it is injected into salivary glands and consequently reduces drooling.


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

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


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