Complete Guide to Medications for Dementia

Introduction

Dementia (commonly known as “brain degeneration” or “senile dementia”) is a growing public health challenge in Hong Kong as the population ages. Although medications cannot cure dementia, they have been proven in clinical practice to slow down disease progression, improve patients’ quality of life, and reduce the burden on caregivers. This article focuses only on the medication aspect, providing a comprehensive overview of commonly used drugs in Hong Kong, their mechanisms of action, side effects, clinical applications, and the latest developments.

1. Cholinesterase Inhibitors

Mechanism of Action

Patients with Alzheimer’s disease have reduced levels of acetylcholine in the brain, leading to impaired memory and cognitive function. Cholinesterase inhibitors work by blocking the enzyme that breaks down acetylcholine, thereby increasing its concentration in the brain and improving nerve transmission.

Common Medications

• Donepezil 

• • Suitable for mild to moderate Alzheimer’s disease.

• • Taken once daily, convenient for patients.

• • Clinical studies show improvement in memory, attention, and daily functioning.

• Rivastigmine 

• • Available in oral and patch forms. The patch reduces gastrointestinal side effects, suitable for patients with sensitive stomachs.

• • Also effective for dementia associated with Parkinson’s disease.
• Galantamine (加蘭他敏膠囊／緩釋劑型)
• • In addition to inhibiting cholinesterase, it modulates nicotinic receptors, enhancing nerve transmission.

• • Some patients experience improved concentration and daily functioning.

Side Effects

• Common: nausea, diarrhea, loss of appetite.
• Cardiac: may cause bradycardia, requiring monitoring of heart function.
• Others: dizziness, insomnia.

Clinical Application

• Suitable for mild to moderate Alzheimer’s disease.
• Choice of drug depends on age, physical condition, and tolerance to side effects.

2. NMDA Receptor Antagonists

Mechanism of Action

In Alzheimer’s disease, glutamate activity in the brain is excessive, leading to nerve cell damage. NMDA receptor antagonists block overstimulation, protecting nerve cells.

Common Medication

• Memantine (美金剛片劑) 

• • Suitable for moderate to severe Alzheimer’s disease.

• • Can be used alone or in combination with cholinesterase inhibitors.

• • Clinical studies show improvement in behavioral symptoms and reduced caregiver burden.

Side Effects

• Common: dizziness, constipation, elevated blood pressure.
• Rare: hallucinations, kidney function problems.

Clinical Application

• Suitable for moderate to severe patients, especially those with behavioral symptoms.
• Dosage adjusted according to kidney function.

3. New Anti-Amyloid Antibody Therapies

Mechanism of Action

Patients with Alzheimer’s disease have accumulation of β-amyloid plaques in the brain, leading to nerve cell death. Antibody drugs target and clear these plaques, slowing disease progression.

Common Medications

• Lecanemab: intravenous infusion every two weeks.
• Donanemab: intravenous infusion every four weeks, treatment can last up to 18 months.

Side Effects

• Brain edema, microhemorrhage.
• Requires regular brain scans for monitoring.

Clinical Application

• Suitable for early Alzheimer’s disease patients.
• Clinical use in Hong Kong is still limited due to high cost.

4. Medications for Psychiatric and Behavioral Symptoms

Common Symptoms

Hallucinations, delusions, anxiety, insomnia, agitation.

Common Medications

• Antipsychotics: for severe hallucinations or delusions. Patients with Lewy body dementia require very low doses and close monitoring.
• Antidepressants: for depression or anxiety. Some drugs can also improve appetite and sleep.
• Hypnotics/Sedatives: short-term use for insomnia or agitation.

Side Effects

• Antipsychotics: increased risk of stroke.
• Antidepressants: possible changes in appetite.
• Hypnotics: increased risk of falls and confusion.

5. Medications for Vascular Dementia

Mechanism of Action

Vascular dementia is related to stroke or cardiovascular disease. Treatment focuses on controlling blood pressure, diabetes, and cholesterol.

Common Medications

• Antihypertensives: prevent recurrent stroke.
• Antiplatelet drugs: reduce clot formation.
• Lipid-lowering drugs: reduce cholesterol.

Clinical Application

• These drugs do not directly improve memory but prevent disease progression.

6. Clinical Highlights 

1. Individualized treatment: psychiatrists tailor medication plans based on age, disease severity, comorbidities, and side effect risks.
2. Combination therapy: medications are often combined with non-pharmacological interventions such as cognitive training, music therapy, exercise, and social activities.
3. Regular follow-up: monitoring side effects and efficacy, adjusting dosage as needed.