Why do antidepressants cause cotton mouth, bad breath?

One of the most common side effects of many medications is cotton mouth, an uncomfortable condition that occurs when the saliva levels in your mouth drop to near zero. Dozens of drug categories lead to dry mouth, from antihistamines to antihypertensives, but one of the most notorious causes of a cottony palate - and so, of bad breath - is antidepressants.

Why do these prescriptions dry out your mouth and encourage halitosis? For the answer to that, you have to look at how the saliva glands work.

Salivary glands: A vital trio

There are three different types of salivary glands in your mouth: the submandibular (located under the floor of your mouth), the sublingual (under the tongue) and the parotid, which is wrapped around your lower jaw, just beneath the hinge. If the latter sounds familiar, it may be because Beastie Boy and hip-hop legend Adam Yauch recently passed away from cancer of the parotid gland.

Your salivary glands emit a constant stream of moisture into your mouth, which keeps your palate wet and minimizes bacterial growth on your tongue. Fun fact: The relatively small submandibular gland is responsible for about 70 percent of your mouth's moisture. That means it pumps out a quart of saliva a day!

These glands get activated by acetylcholine, a neurotransmitter found in your nervous system. And, for good or ill, antidepressants inhibit the uptake of this molecule. Specifically, they prevent acetylcholine from reaching M3 muscarinic receptors, which can be found in your salivary glands.

The result: cotton mouth.

A study published in the journal Acta Psychiatrica Scandinavica found that the antidepressants maprotiline, nortriptyline, clomipramine, imipramine and amitriptyline cause the worst cotton mouth.

What you can do for it

Since quitting antidepressants is not a very good idea, here are some tips for managing cotton mouth.

- Sip on water or suck on ice chips throughout the day.

- Regularly pop a specialty mouth-wetting lozenge in your mouth.

- Brush or rinse with specialty breath freshening, alcohol-free products, especially before bed and after waking.