ALZHEIMERS AND PARKINSONS DRUGS

Chapter 24: Drugs for Alzheimer's and Parkinson's Disease

Objectives

Explain how different classes of drugs are used to treat Alzheimer’s disease and Parkinson’s disease.
List the names, actions, usual adult dosages, possible side effects, and adverse effects of drugs for Alzheimer’s disease.
Describe what to do before and after giving drugs for Alzheimer’s disease.
Explain what to teach patients taking drugs for Alzheimer’s disease and their families or caregivers, including what to do, what not to do, and when to call the prescriber.
Describe life span considerations for drugs for Alzheimer’s disease.
List the names, actions, usual adult dosages, possible side effects, and adverse effects of drugs for Parkinson’s disease.
Describe what to do before and after giving drugs for Parkinson’s disease.
Explain what to teach patients taking drugs for Parkinson’s disease and their families or caregivers, including what to do, what not to do, and when to call the prescriber.
Describe life span considerations for drugs for Parkinson’s disease.

Overview of Alzheimer’s and Parkinson’s Disease

Alzheimer’s Disease
  - Most common form of dementia.
  - Characterized by progressive, incurable condition that destroys brain cells.
  - Leads to a gradual loss of intellectual abilities, affecting the performance of Activities of Daily Living (ADLs), memory, and reasoning.
  - Pathologic changes include:
    - Formation of large amounts of Abeta protein clumping together into plaques between cells.
    - Formation of tangles within neurons due to other twisting proteins.
  - The first symptom experienced is mild forgetfulness.
  - In late stages, patients will require total care.
  - Neurotransmitter levels (specifically acetylcholine, and the action of acetylcholinesterase) are lower.
Parkinson’s Disease
  - Neurodegenerative disease marked by slow, progressive degeneration of the nervous system with an unknown cause.
  - Risk factors include age (particularly older than 50), genetics, environmental factors, and abnormal genes.
  - Symptoms commonly present as resting tremors, rigidity, stiffness, stooped posture, and balance issues.
  - There is a decrease in dopamine levels and nerve cell degeneration in the substantia nigra.
  - Drug therapy aids in controlling symptoms and prolonging normal function.

Biologic Agents for Alzheimer’s Disease

Aducanumab (Aduhelm)
  - Focuses on the underlying biology of Alzheimer’s Disease.
  - Intended Responses:
    - Prevents beta-amyloid clumping into plaques.
    - Removes beta-amyloid plaques.
    - Decreases cognitive and functional decline.
  - Side Effects:
    - Headache, dizziness, nausea, confusion, vision changes.
  - Adverse Effects:
    - Allergic reactions.

Classes of Drugs for Alzheimer’s Disease

Cholinesterase Inhibitors/Acetylcholinesterase Inhibitors
- Reduce acetylcholinesterase enzyme activity.
Memantine
  - Functions to prevent overstimulation of brain receptors.
  - Intended Responses:
    - Temporarily decreases dementia and inhibits the degradation of acetylcholine.
    - Slows the progression of symptoms and improves cognitive function.

Common Drugs for Alzheimer’s Disease

Donepezil (Aricept)
Galantamine (Razadyne)
Memantine (Namenda)
Rivastigmine (Exelon)

Side Effects and Adverse Effects of Drugs for Alzheimer’s Disease

Common Side Effects:
- Nausea, vomiting, diarrhea, stomach cramps, headaches, dizziness, fatigue, weakness, insomnia, anorexia.
Adverse Effects:
- Abnormal heart rhythms, gastrointestinal bleeding, difficulty urinating, seizures, shortness of breath, hallucinations.

Administering Drug Therapy for Alzheimer’s Disease

Before Administration:
- Assess baseline vital signs, weight, gastrointestinal (GI) status, urinary status, and cognitive function.
- Evaluate swallowing ability and check for any liver/kidney problems.
After Administration:
  - Monitor vital signs and daily weights.
  - Assess heart status and monitor intake and output (I&O) along with any GI discomfort.
  - Continually evaluate cognitive function.
  - Watch for seizures and other side effects.
Patient Teaching (Include Caregiver):
  - Take medications as prescribed; do not crush extended-release formulations.
  - Ensure appropriate medical follow-up and report any side effects promptly.
  - It is best to take medications with food to avoid GI upset.
  - The primary goal is temporary improvement in cognitive function.

Life Span Considerations for Drugs for Alzheimer’s Disease

Older Adults:
  - Use caution with patients who have a history of GI bleeding, liver, kidney, or heart disease.
  - Rivastigmine (Exelon) should be used cautiously in patients with asthma or COPD.
  - Older, frail females should not exceed 5 mg/day of Donepezil (Aricept) due to increased risk of incontinence.

Overview of Parkinson’s Disease

Characterized by slow, progressive degeneration of the nervous system with an unknown cause.
Risk factors include age (greater than 50), genetics, and environmental factors.
Associated with decreased dopamine levels due to degeneration of nerve cells in the substantia nigra.
Classic symptoms include resting tremors, muscular rigidity, stiffness, stooped posture, and balance instability.
Medications aim to facilitate movement and prolong the patient's normal functions.

Brain Changes in Parkinson’s Disease

Degeneration of nerve cells in the substantia nigra leads to decreased dopamine production.
Results in fewer connections between nerve cells in the basal ganglia, leading to decreased smooth movements.

Types of Drugs for Parkinson’s Disease

Dopaminergic Agents and Dopamine Agonists:
- Enhance dopamine activity in the brain.
COMT Inhibitors:
- Enable more levodopa to reach the brain.
MAO-B Inhibitors:
- Inhibit enzymes that break down dopamine in the brain.
Anticholinergics:
  - Block cholinergic nerve impulses that help control muscles.
  - Intended Responses:
    - Decrease signs and symptoms associated with Parkinson’s Disease and relieve tremor and rigidity.

Side Effects and Adverse Effects of Drugs for Parkinson’s Disease

Common Side Effects:
- Dizziness, nausea, hypotension.
Adverse Effects:
- Depression with suicidal tendencies, neutropenia, neuroleptic malignant syndrome, life-threatening CNS depression, shock, acute myocardial infarction, narcolepsy, rhabdomyolysis.

Administering Drugs for Parkinson’s Disease

Before Administration:
  - Compile a complete list of all drugs the patient is currently using.
  - Assess baseline vital signs including blood pressure, heart rate, and respiratory rate.
  - Evaluate the patient's neurologic and mental status, dyskinesia, rigidity, tremors, gait, and swallowing ability.
  - Ascertain any kidney or liver disease history.
After Administration:
  - Monitor vital signs every 4 to 8 hours.
  - Reassess mental status and inquire about any side effects experienced.
  - Assess bladder distention and monitor intake and output, as well as skin conditions.
Patient Teaching (Include Caregiver):
  - Take medications as prescribed and do not crush extended-release formulations.
  - Avoid doubling up on doses.
  - Educate that medications are used to control symptoms and are not a cure.
  - Advise to avoid overexertion on physical activities and prevent falls or injuries.
  - Recommend taking medications with food or milk to minimize GI upset.
  - Schedule regular eye exams if using anticholinergics.
  - Caution against excessive chocolate and caffeine intake, and remind to stay cool in hot weather.

Life Span Considerations for Drugs for Parkinson’s Disease

Pregnancy and Breastfeeding:
- Limited testing conducted; use only when the benefits outweigh the risks.
Bromocriptine (Parlodel):
- Not recommended during pregnancy and can suppress breast milk production.
Older Adults:
  - More sensitive to drug effects; advise changing positions slowly to prevent dizziness.
  - Potential for confusion, hallucinations, and uncontrolled body movements.
  - Recommend using handrails on stairs to ensure safety.

Specific Drug: Benztropine (Cogentin)

Classification:
- Anticholinergic; Antiparkinson drug.
Route of Administration:
- IM (intramuscular); used only for dystonia and tremors.
Mechanism of Action:
- Selectively blocks central cholinergic receptors and balances dopaminergic activity to reduce the severity of symptoms such as rigidity.
Adverse Effects and Assessments:
- Monitor elderly clients for confusion, disorientation, agitation, and symptoms akin to psychosis.
- Watch for drowsiness, dry mouth, blurred vision, urinary retention, constipation, and decreased sweating.

References

Workman, M.L. & LaCharity, L. (2023). Understanding pharmacology: Essentials for medication safety (3rd ed.). Elsevier.