This is an important read from the NY Times:
April 24, 2017
By C. CLAIBORNE RAY
Q. What is it about so many medications that causes dryness, especially in the mouth?
A. Dry mouth, also called xerostomia, is a frequent side effect of many commonly prescribed drugs, according to a 2015 review of research on treating dry mouth published in the journal Therapeutics and Clinical Risk Management.
Among the common culprits in xerostomia are drugs like benzodiazepines, prescribed for their calming effect; antidepressants, particularly selective serotonin reuptake inhibitors; some oral drugs used to reduce blood sugar; respiratory agents; quinine; some drugs used to treat high blood pressure, like calcium channel blockers and diuretics; drugs used to treat excess urination; some nonsteroidal anti-inflammatory drugs; opioids; glucosamine supplements; and magnesium hydroxide, a component of milk of magnesia.
Some of the drugs are prescribed for their drying effect, which may be magnified in older people if they are taking several of them.
Not all the drying mechanisms of the various drugs involved are fully understood. Some of them are known to suppress the action of receptors on nerve cells in various glands, including the salivary glands, that produce fluids.
These so-called anticholinergic drugs block the action of an important neurotransmitter called acetylcholine that normally binds to these special receptors to signal the glands to work.
The drying effect can also involve other mucus membranes, like those around the eyes and in the digestive system. question@nytimes.