What Causes Dry Mouth?
Medications are the most common cause of dry mouth in the general population and especially in older adults, primarily through anticholinergic mechanisms, with polypharmacy substantially increasing risk. 1, 2
Medication-Induced Causes
Anticholinergic Medications
- Centrally acting anticholinergics (scopolamine, atropine) directly block muscarinic receptors, causing dry mouth along with blurred vision, dilated pupils, urinary retention, and sedation 1
- Tricyclic antidepressants have significant anticholinergic effects, making them common xerostomia culprits 1
- Cyclobenzaprine produces dry mouth as one of its most common adverse reactions through anticholinergic mechanisms 1
Cardiovascular Medications
- Beta-blockers (atenolol, metoprolol, propranolol) cause dry mouth through anti-adrenergic effects, with atenolol producing more pronounced effects than propranolol 1
- Centrally acting antihypertensives like clonidine cause dry mouth as one of their most prevalent adverse effects through alpha-adrenergic mechanisms 1
Psychotropic Medications
- SSRIs (particularly fluoxetine) cause dry mouth with higher doses associated with greater frequency and severity of anticholinergic side effects 1
- Bupropion commonly causes dry mouth as a side effect 1
Other Medication Classes
- Opioids commonly cause dry mouth as an adverse effect 1
- Stimulant medications like phentermine and lisdexamfetamine (Vyvanse) cause dry mouth in a significant percentage of users 1, 3
- Anti-obesity medications including phentermine/topiramate and naltrexone/bupropion list dry mouth as a common side effect 1
- Antihistamines, analgesics, antipyretics, antibiotics, and vaccines can all contribute to reduced saliva flow 4, 1
Important caveat: The greater the number of medications taken (polypharmacy), the greater the anticholinergic burden and the higher the likelihood of dry mouth, making elderly patients particularly vulnerable 1, 5
Systemic Disease Causes
Autoimmune Conditions
- Sjögren's syndrome is characterized by lymphocytic infiltration of lacrimal and salivary glands with secondary compromise of gland function, affecting approximately 0.4% of the population with a female-to-male ratio of 20:1 4
- Sicca syndrome presents with abrupt onset dry mouth, usually without dry eyes, and can occur independently of Sjögren's syndrome 1, 6
- Rheumatoid arthritis can cause salivary gland hypofunction 4
Other Medical Conditions
- Diabetes mellitus can trigger xerostomia 7
- Sarcoidosis may cause reduced salivation 7
- CNS disorders can disrupt normal salivary function 7
Iatrogenic Causes
- High-dose radiation therapy for head and neck cancers causes salivary gland damage and hypofunction 8, 9
Lifestyle and Environmental Factors
- Dehydration from any cause worsens the perception and severity of xerostomia 1
- Alcohol and caffeine intake contribute to dry mouth symptoms 2
- Chronic nasal obstruction forcing mouth breathing can cause xerostomia 7
- Fluid intake restrictions compound medication-induced dry mouth 1
Age-Related Factors
- Salivary flow rate declines with age, making older adults more susceptible even without other risk factors 4
- Elderly patients face substantially higher risk due to multiple medications combined with age-related decline in salivary flow 1
Important Clinical Pitfalls
Do not assume xerostomia equals low salivary flow: Subjective feelings of dryness often do not match objective measurements of glandular function, as environmental and psychological stressors influence perception 4, 6
Rule out mimicking conditions: Candidiasis, burning mouth syndrome, and dysphagia (which increases saliva in the mouth due to reduced clearance despite actual reduced production) can present similarly 4, 1
Consider paradoxical effects: AChE inhibitors used for Alzheimer's disease actually increase saliva production, contrasting with most other medications 4, 1