The bothersome combination of dry mouth and bad breath, also known as xerostomia, can be chalked up as yet another common problem caused by prescription drug use.
Xerostomia is not to be confused with halitosis, or bad breath, which is typically caused by systemic diseases, gastrointestinal and/or upper respiratory tract disorders, and microbial metabolism from your tongue, saliva or dental plaque.
Common Causes of Dry Mouth and Bad Breath (Xerostomia)
First of all, it’s important to realize that xerostomia is NOT a disease in and of itself. Rather it is a common side effect of prescription- and OTC drugs.
It can also be a symptom caused by certain physical disorders and diseases that target your salivary glands and/or tear ducts, some of which are mentioned below.
Specific types of medications that are known to affect your salivary glands include drugs for: 
Cancer treatments such as chemotherapy and radiation also tend to cause dry mouth.
Other Non-Drug Causes
• Nerve damage in your head or neck that affect your salivary glands
• Sjogren’s syndrome (an autoimmune disease, causes xerostomia and dry eyes)
• Endocrine disorders
• Alzheimer’s disease
• Stroke
• Anxiety disorders and depression
Interestingly, xerostomia can also be a sign of nutritional deficiencies (some drugs are also known to cause a variety of nutritional deficiencies).
Naturally, if you already suffer with dry mouth and/or bad breath, you can certainly make it worse for yourself by smoking, drinking alcohol, using alcohol-containing mouthwashes, and drinking caffeine. All of these behaviors will exacerbate your problem, so avoid them as much as possible.
Snoring, and constantly breathing through your mouth instead of your nose can also cause your mouth to dry out further.
If you’re a “mouth-breather,” pay conscious attention to how you breathe, and train yourself to breathe through your nose.
Quitting snoring, however, can be trickier, since it’s happening while you’re asleep. For a list of strategies to combat snoring, please see this previous article.
Why You Should Be Concerned About Dry Mouth
Dry mouth may seem like a trivial concern to many, especially if you’ve never experienced it. But aside from just being bothersome, the most hazardous consequence of dry mouth is the increase of tooth decay, which can impact your overall health if it goes too far. (Naturally, it will also affect your pocketbook, as the cost of dental services keep rising.)
Saliva serves several functions, one of which is to protect and help repair your teeth from the constant assaults mounted by bacteria and your diet. Without sufficient amounts of saliva, your teeth are in large part left unprotected.
To illustrate just how hazardous some drugs can be for your dental health, a previousstudy, using rats, showed that clonidine (Catapres) — a high blood pressure medication that has also become popular in treating attention deficit hyperactivity disorder (ADHD) in children — resulted in 84 percent more cavities.
Xerostomia can also lead to thrush (oral candidiasis), a yeast infection of the mouth or throat, and can also have a negative impact on quality of life by affecting your:
• Dietary habits
• Nutritional status
• Speech
• Taste
• Tolerance to dental prosthesis