Drug-Induced Dry Mouth

More than just an annoyance, xerostomia requires dilligent treatment to prevent a decline in health.

Dry mouth (xerostomia) can change speech patterns, allow dentures to rub, and contribute to dental caries. It also changes dietary preferences: who wants to eat peanut butter or saltines with a dry mouth? It may alter the sufferer’s nutritional status, causing vitamin deficiencies and caloric insufficiency—once salivary flow is reduced by half, chewing and swallowing become problematic.¹ Dry mouth can change appearance, too; lipstick on the teeth is a clue that the wearer may have xerostomia.

Up to 30% of Americans experience xerostomia,^2-8 with elders affected more.⁹ Many things cause a sticky, dry mouth— scary movies, dental cotton before a procedure, heredity, snoring, or mouthbreathing during a cold—but medication is the most frequent cause.^10-12 Most medications associated with dry mouth affect the sympathetic nervous system, thickening and limiting the flow of saliva.¹³

Saliva

Three pints of saliva: that’s how much the average healthy person makes daily. It’s 99% water and 1% proteins, enzymes, and electrolytes.^13-16 Saliva’s role is more complex than just moistening food as we chew. It contains the enzyme amylase which breaks down select starches into maltose and dextrin, initiates fat breakdown, and starts digestion.¹⁷ Saliva’s calcium and phosphate content restores those leached substances to tooth enamel. It also contains role-specific proteins (eg, antibacterial histatins, protective statherins, lubricating mucins).¹⁸ Right before a person vomits, the brain signals the salivary glands to increase saliva secretion. This decreases oral acidity, protecting the mucosa and teeth from acidic emesis.¹⁷ It has numerous other roles as well.

When dry mouth becomes chronic, dental health declines and patients may develop infection. Thrush (candida albicans) infection is common, especially in patients who wear dentures, smoke, take corticosteroids, or have diabetes.^10,19,20 The loss of salivary proteins and electrolytes— which inhibit cariogenic microorganisms and buffer oral acids—accelerates tooth decay.¹⁰ Table 1^10,20-28 lists the nonpharmacologic causes of dry mouth.

Drugs and Dry Mouth

Several hundred medications can cause or exacerbate xerostomia,^10-12 including antihypertensives, antidepressants, analgesics, tranquilizers, diuretics, and antihistamines. ²⁹ These drugs affect the saliva’s quantity and possibly quality, but usually the problem is temporary or reversible. The chewing gum manufacturer Wm. Wrigley Jr. Company’s Web site—www .drymouth.info—provides a searchable list of drugs associated with dry mouth. Their explanation of the complexities of identifying drugs that cause dry mouth (see http://drymouth.info/practitioner/complexities.asp) highlights the inadequacies of our current adverse event, adverse effect, and side effect monitoring systems.

Treatment

For drug-induced xerostomia, using the lowest effective dose or switching to an alternative medication may help. If dry mouth is associated with correctable causes and correction of underlying causes doesn’t improve the condition, several additional steps are critical. Patients should see a dentist and have fluoride-containing sealants applied to seal pits, fissures, and rough restorative margins. The dentist may recommend a regular dose of fluoride and an antibacterial dental varnish containing 1% chlorhexidine and 1% thymol to prevent dental caries. Chewing xylitol gum enhances salivary flow and helps control mutans strep, but note that elders who wear dentures may be unable to chew gum. Patients should be encouraged to conduct a daily mouth examination, checking for red, white, or dark patches, ulcers, or tooth decay.³⁰

Sipping water or sucking on ice chips throughout the day may moisturize the mucosa and possibly alleviate symptoms. If this is not effective, artificially moisturizing the mucosa is a possible next step. Saliva substitutes are available in several dosage forms (Table 2). They are best used at bedtime and periodically throughout the day; their relief is temporary and efficacy varies.^31-33

Rather than using a commercial product, some patients find that mixing equal parts water and glycerin and spraying the mixture regularly in the mouth offers periodic relief. In addition to using exogenous moisturizers, patients will find that choosing low-sugar, low-acid, moist foods will make eating easier. They should avoid alcohol-containing mouth rinses and washes that may desiccate the oral mucosa, choosing a commercial mouthwash designed for people with dry mouth instead. At night, running a room humidifier adds moisture to the air and can provide some relief.

Drug Treatment

Sometimes patients will need prescription- strength medication. Cevimeline is an oral cholinergic agent approved for symptomatic treatment of dry mouth in patients with Sjögren’s syndrome. Common side effects include excessive sweating, nausea, rhinitis, and diarrhea. Patients must increase their fluid intake or they may develop or confound existing dehydration. If visual blurring occurs, it is a serious concern. Cevimeline’s use in radiation-induced xerostomia is off label, but can sometimes be helpful.²⁸

Oral pilocarpine, also a cholinergic agonist, is approved for salivary gland hypofunction caused by radiotherapy for cancer of the head and neck or in patients with Sjögren’s syndrome in the absence of ophthalmologic and cardiorespiratory contraindications. It, too, stimulates exocrine function. Side effects include sweating, nausea, rhinitis, diarrhea, flushing, and polyuria. Dose-related hypotension, hypertension, bradycardia, and tachycardia can occur, as can blurred vision. Patients must be able to increase fluid intake.³²

Conclusion

Dry mouth, especially when it is chronic, drastically alters patients’ lives. They will find that the sore mucous membranes and gums, cracked lips and split corners of the mouth, and a rough, painful tongue make eating impossible. When teeth feel like razors, spicy foods set off alarms, and sleep eludes them because they wake to sip water, they need help. Pharmacists can recommend appropriate and soothing interventions. PT

Ms. Bartok is a pharmacist and freelance writer from eastern Connecticut.

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