Dementia Medications and Supplements: Managing Cholinesterase Inhibitors, Memantine, and Anticholinergic Burden
Medications for cognitive decline and dementia work by different mechanisms to slow progression or manage symptoms. However, these medications interact with supplements and some supplements have anticholinergic effects that may worsen cognitive function when combined with dementia medications. For caregivers managing medication regimens in those with cognitive impairment, understanding these interactions is essential for maintaining cognitive function and safety.
Cholinesterase Inhibitors
Cholinesterase inhibitors (donepezil, rivastigmine, tacrine) are used to treat Alzheimer's disease and other dementias. They work by inhibiting acetylcholinesterase, the enzyme that breaks down acetylcholine (a neurotransmitter important for memory and cognition). By preventing acetylcholine breakdown, these medications increase acetylcholine availability in the brain.
Common side effects include nausea, vomiting, diarrhea, and muscle weakness. Gastrointestinal side effects can be managed with dietary adjustments (small, frequent meals) and timing medication with food.
Memantine
Memantine is an NMDA receptor antagonist used to treat moderate-to-severe Alzheimer's disease. It works by blocking excess glutamate signaling, which is thought to contribute to neurodegeneration. It may be used alone or combined with cholinesterase inhibitors.
Side effects are generally mild and include dizziness, headache, and constipation. Memantine is usually taken twice daily.
Anticholinergic Burden and Cognitive Function
Anticholinergic medications and supplements block acetylcholine signaling and increase the risk of cognitive impairment, delirium, and falls in older adults—particularly those with existing cognitive decline. When anticholinergic compounds are added to someone on cholinesterase inhibitors, there's a direct pharmacological opposition: the cholinesterase inhibitor tries to increase acetylcholine, while the anticholinergic agent blocks it.
Over-the-counter anticholinergic medications include:
Antihistamines: Diphenhydramine (Benadryl) and similar first-generation antihistamines are strongly anticholinergic and should be avoided in older adults with cognitive impairment. They increase delirium risk. Second-generation antihistamines (cetirizine, loratadine) are less anticholinergic and preferable.
Antispasmodics: Medications for urinary incontinence (oxybutynin) and muscle spasms are highly anticholinergic and should be carefully evaluated in those with cognitive decline.
Sleep aids: Over-the-counter sleep aids (often containing diphenhydramine) are anticholinergic and worsen cognitive function. Alternatives should be sought.
Anticholinergic supplements:
Herbal supplements with anticholinergic properties include: scopolamine (found in some traditional medicines); atropine-containing plants; and some nightshade family plants (deadly nightshade, henbane). These should be avoided entirely in those with cognitive decline. Additionally, many herbal preparations contain poorly characterized compounds; older adults with cognitive impairment should avoid unfamiliar herbal products.
Valerian root and other sedating herbs, while not directly anticholinergic, increase sedation and confusion in older adults and should be used cautiously if at all.
Supplements That May Support Cognitive Function
While evidence is limited, some supplements are being researched for cognitive benefit in dementia:
Omega-3 fatty acids (particularly DHA): DHA is a component of neuronal membranes; adequate DHA intake may support cognitive function. Some studies show modest benefit in early cognitive decline, though evidence in established dementia is mixed.
B vitamins (B6, B12, folate): These vitamins are involved in homocysteine metabolism; elevated homocysteine is associated with increased Alzheimer's risk. Ensuring adequate B vitamin status is important, particularly given that some dementia medications may affect B vitamin absorption or metabolism.
Vitamin E: Antioxidant vitamin E has been studied in Alzheimer's disease with mixed results. Very high doses may increase mortality risk; moderate dietary intake is preferable to supplementation.
Ginkgo biloba: Mixed evidence for cognitive benefit, and concerns about bleeding risk and interaction with other medications make it a less preferred option.
Drug-Nutrient Interactions With Dementia Medications
Donepezil and some other cholinesterase inhibitors are metabolized by the liver; interactions with other substances that induce or inhibit liver enzymes could theoretically affect medication levels. However, significant clinical interactions are rare.
Memantine is excreted renally (through kidneys); in those with reduced kidney function, memantine levels may accumulate. Dosing adjustments may be necessary, and supplements affecting kidney function should be avoided.
Gastrointestinal Support With Cholinesterase Inhibitors
Cholinesterase inhibitors increase acetylcholine throughout the body, including in the GI tract, causing increased motility and diarrhea in some individuals. Dietary modifications (smaller, frequent meals; low-fat diet; adequate hydration) often help. Probiotics may support gut health, though specific benefits in this context are unclear. Antidiarrheal medications should be used cautiously, as they may reduce medication absorption.
Nutritional Support in Dementia
Older adults with dementia often have difficulty eating and may become malnourished. Ensuring adequate protein, calories, vitamins, and minerals is important. Liquid nutritional supplements may be helpful when whole food intake is inadequate. Hydration is critical, as dehydration can worsen cognitive function and increase infection risk.
Safe Supplement and Medication Management
For those on dementia medications: avoid all anticholinergic medications and supplements unless specifically approved by healthcare providers; avoid first-generation antihistamines (diphenhydramine); maintain regular follow-up to assess medication effectiveness and side effects; discuss all supplements with healthcare providers before starting; ensure adequate nutrition and hydration; and monitor for changes in cognition or function that might warrant medication adjustment.
This article is for informational purposes and should not replace professional medical advice. Questions about dementia medications or supplements should be discussed with the healthcare provider managing the dementia. MercyAssistedCare.org Wellness Team | July 2026