Drooling (sialorrhea), or excessive saliva, results from difficulty swallowing and is a frequent symptom in PD. Most of the time, drooling is merely an annoyance. However, sometimes it’s an embarrassment, and sometimes it’s even a hazard: aspiration of saliva (swallowing saliva into your lungs) can cause pneumonia. Saliva is the watery liquid that coats your food, making it slippery and easier to swallow.
Saliva contains enzymes that break down complex carbohydrates and starches, making them easier to digest, and also contains bactericidal chemicals that fight tooth decay. Swallowing removes saliva and prevents it from accumulating in your mouth and throat. It is an active process requiring coordination of the circular muscles of your throat and esophagus. In PD, the muscles of your tongue, palate, throat, and esophagus may be affected, becoming rigid and slow and losing their ability to propel food down-ward.
Gravity also aids in swallowing. During the day, when your head is erect (when you are seated or standing), saliva is propelled by your tongue, palate, and throat, and moves down your esophagus into your stomach. At night, however, with your head down, gravity no longer helps and saliva drips onto your pillow.
You may wake in the morning to a wet pillow. Saliva is produced by your salivary glands: the parotid, sub-maxillary, and sub-lingual glands located in the floor of your mouth and at the angle of the jaw. Although the production of saliva is automatic, production can be increased in response to eternal events, such as the sight, smell, or taste of food (even the thought of food). The ANS controls the production of saliva through releasing acetylcholine, which stimulates receptors on cells of the salivary glands. In addition to the rigidity of your throat and esophageal muscles associated with PD, drooling may also result from increased production of saliva secondary to over-activity of your ANS.
The first approach to treating drooling is education. Understanding the reasons you drool can help you tackle the cause. For example, sleeping with your head raised allows gravity to help you swallow your saliva. Chewing sugarless gum stimulates the circular muscles of your throat and also helps you swallow your saliva. These suggestions help, but eventually, as PD progresses, they may not be enough. The next approach is use of anticholinergic drugs, which block the actions of acetylcholine at cholinergic receptors on the salivary glands.
Artane and Cogentin both work in this way to decrease drooling. Trihexiphenidyl also blocks acetylcholine receptors in your body, but may cause confusion, delusions, memory loss, blurred vision, constipation, and/or urinary retention. Few patients can tolerate the high doses required to control drooling without side effects.
Darifenacin (Enablex) and tro-spium (Sanctura) are anticholinergic drugs that are helpful in treating overactive bladder. As neither drug enters the brain, both can be used to treat drooling without causing confusion, delusions, or memory loss. However, these drugs are expensive and as they are not yet FDA-approved to control drooling, it is unlikely your insurance company will pay for them. For some people, however, the price is worth the result.
One final approach is Botox (botulinum toxin), which is a large protein molecule that blocks the release of acetylcholine onto muscles and can stop the secretion of acetylcholine by the salivary glands. Because of its size, it is difficult for Botox to go anywhere and thus the effects are confined to the site of injection. When injecting Botox for drooling, care must be taken to avoid the muscles of swallowing located at the base of the mouth. Such an injection can temporarily cause an inability to swallow.