Dry Mouth

Dry mouth (xerostomia) is the subjective sensation of oral dryness, usually accompanied by salivary gland hypofunction (hyposalivation), defined by an unstimulated whole saliva flow under 0.1 mL/min or a stimulated flow under 0.7 mL/min. Some patients feel dry without objective hyposalivation, and some have hyposalivation without symptoms.

• Prevalence is about 10 to 30 percent of adults and up to 40 percent or more of older people.
• Medicine induced dryness is the commonest cause: anticholinergics (oxybutynin, tolterodine, tricyclic antidepressants, antipsychotics, antihistamines, hyoscine), antidepressants (SSRIs, SNRIs), diuretics, antihypertensives (clonidine, beta blockers), opioids, benzodiazepines, decongestants, bronchodilators, and antiretrovirals. Risk rises with the number of medicines.
• Systemic: Sjogren syndrome, rheumatoid arthritis, systemic lupus erythematosus, systemic sclerosis, diabetes mellitus, HIV (diffuse infiltrative lymphocytosis syndrome), hepatitis C, sarcoidosis, amyloidosis, IgG4-related disease, dehydration, renal failure, anxiety and depression, and hormonal changes in menopause.
• Local: head and neck radiotherapy (dose dependent gland damage), radioiodine, salivary gland obstruction or infection, mouth breathing, tobacco, alcohol, cannabis, and methamphetamine.
• Complications: rampant dental caries (especially cervical and root caries), candidiasis, gum disease, dysgeusia, burning mouth, difficulty with chewing, swallowing and speaking, denture intolerance, halitosis, and ascending sialadenitis.

• Dry, sticky mouth, thirst, need to sip water to swallow dry food, difficulty speaking, waking at night with dryness, altered or metallic taste, burning, sore tongue, cracked lips and corners of the mouth, bad breath, and new caries.
• Signs: dry, glassy, red mucosa that sticks to the mirror; no pooling of saliva in the floor of the mouth; lobulated or fissured depapillated tongue; thick, ropey saliva; angular cheilitis; erythematous candidiasis; cervical caries; enlarged or tender salivary glands; absence of saliva when the major glands are milked.
• Sjogren features: dry eyes (gritty, burning), arthralgia, Raynaud phenomenon, rashes, fatigue, parotid swelling, neuropathy.
• Red flags: unilateral or hard salivary gland swelling, rapidly enlarging gland, neck nodes, weight loss, or night sweats (lymphoma complicates Sjogren syndrome).

• Clinical history (including a full medicine review) and examination of mouth, glands and eyes.
• Salivary flow measurement: unstimulated whole saliva collected by spitting for 5 minutes (normal over 0.3 mL/min; under 0.1 mL/min is severe hypofunction); stimulated flow with citric acid or chewing paraffin wax.
• Blood tests: FBC, glucose or HbA1c, urea and electrolytes, calcium, thyroid function, ESR, CRP, antinuclear antibodies, anti-Ro (SSA) and anti-La (SSB), rheumatoid factor, immunoglobulins, hepatitis C and HIV serology, and IgG4 if indicated.
• Tests for Sjogren syndrome: Schirmer test (under 5 mm in 5 minutes), ocular staining score, salivary gland ultrasound, labial minor salivary gland biopsy.
• Sialography or ultrasound for obstruction or sialolith; CT or MRI for masses.
• Differentials: dehydration, anxiety, depression, burning mouth syndrome, diabetes insipidus, and nasal obstruction with mouth breathing.

Remove or reduce causes

• Review the medicine list with the prescriber; stop or substitute drugs with anticholinergic effect when possible (for example, replace oxybutynin with mirabegron 25 mg daily; replace amitriptyline with a less anticholinergic option), reduce doses, and shift timing to the evening.
• Treat dehydration, diabetes, anxiety and depression.
• Stop smoking and cannabis, and reduce alcohol and caffeine.

Stimulate and replace saliva

• Frequent sips of water; sugar free chewing gum or xylitol lozenges and sour sugar free sweets (stimulates residual function); avoid sugary or acidic drinks.
• Humidifier at night, nasal breathing, lip balm.
• Saliva substitutes: carboxymethylcellulose or mucin based sprays, gels or lozenges, applied as often as needed and before meals and bed; gel at night.
• Avoid alcohol containing mouthwashes and toothpastes with strong foaming agents; use mild or sodium lauryl sulfate free products.

Systemic sialogogues (for residual gland function)

• Pilocarpine hydrochloride 5 mg orally three times daily with meals, taken for 8 to 12 weeks to judge response (may be raised to 10 mg three times daily); side effects: sweating, flushing, urinary frequency, nausea; contraindicated in uncontrolled asthma, narrow angle glaucoma, acute iritis, severe chronic obstructive pulmonary disease and significant bradycardia or heart block.
• Cevimeline 30 mg orally three times daily (similar cautions) where available.

Prevent oral complications (most important)

• Fluoride toothpaste 5000 ppm twice daily on dental prescription, brushing after meals; fluoride mouthwash 0.05 percent daily; fluoride varnish 22,600 ppm every 3 to 6 months; chlorhexidine 0.2 percent mouthwash when plaque control is poor; dietary advice with limits on sugar frequency.
• Dental review every 3 to 6 months; oral hygiene instruction and denture care.

Treat complications

• Oral candidiasis: miconazole oral gel 2.5 mL four times daily for 7 days (avoid with warfarin), or nystatin 100 000 units/mL suspension 1 mL four times daily for 7 days, or fluconazole 50 mg orally daily for 7 to 14 days (check interactions with warfarin, statins and QT-prolonging drugs); treat dentures overnight with chlorhexidine or nystatin.
• Angular cheilitis: miconazole 2 percent cream twice daily.
• Sialadenitis: hydration, massage, sialogogues, and amoxicillin clavulanate 625 mg orally three times daily for 7 days.

Sjogren syndrome and radiotherapy

• Refer to rheumatology (hydroxychloroquine 200 mg twice daily for fatigue and arthralgia, ophthalmology for dry eyes, lymphoma surveillance); radiotherapy induced xerostomia: salivary sparing techniques, pilocarpine 5 mg three times daily during and after radiotherapy, and dental assessment before treatment.

Follow up

• Review at 4 to 8 weeks; evaluate dental caries risk at each visit; refer if gland swelling or systemic features arise.