Pharmacology for Nurses

💊Pharmacology for Nurses Unit 10 – Myasthenia Gravis & Alzheimer's Medications

Myasthenia gravis and Alzheimer's disease are two distinct neurological conditions affecting muscle function and cognitive abilities, respectively. Both disorders involve disruptions in acetylcholine signaling, leading to characteristic symptoms and requiring specialized treatment approaches. Understanding these conditions is crucial for nurses, as they often encounter patients with MG or AD in various healthcare settings. Proper assessment, medication management, and patient education are key components of providing effective care and improving outcomes for individuals affected by these challenging disorders.

What's the Deal?

  • Myasthenia gravis (MG) is an autoimmune neuromuscular disorder that causes weakness and fatigue in voluntary muscles
  • Occurs when the immune system mistakenly attacks and destroys acetylcholine receptors (AChRs) at the neuromuscular junction
  • Leads to impaired communication between nerves and muscles, resulting in muscle weakness and fatigue
  • Symptoms can vary in severity and may fluctuate over time, often worsening with activity and improving with rest
  • Common symptoms include drooping eyelids (ptosis), double vision (diplopia), difficulty speaking (dysarthria), and trouble swallowing (dysphagia)
  • MG can affect individuals of any age but is most commonly diagnosed in women under 40 and men over 60
  • Alzheimer's disease (AD) is a progressive neurodegenerative disorder characterized by cognitive decline, memory loss, and changes in behavior and personality
  • AD is the most common cause of dementia, accounting for 60-80% of all dementia cases

Key Players

  • Acetylcholine (ACh): a neurotransmitter responsible for transmitting signals from nerves to muscles at the neuromuscular junction
  • Acetylcholine receptors (AChRs): proteins on the surface of muscle cells that bind to ACh, allowing the muscle to contract
  • Autoantibodies: antibodies produced by the immune system that mistakenly target and destroy the body's own tissues, such as AChRs in MG
  • Thymus gland: an organ located in the chest that plays a role in the development of the immune system; abnormalities in the thymus (hyperplasia or tumors) are associated with MG
  • Beta-amyloid plaques: abnormal accumulations of beta-amyloid protein fragments that build up between nerve cells (neurons) in the brain, contributing to the development of AD
  • Neurofibrillary tangles: abnormal accumulations of tau protein inside neurons that disrupt their function and contribute to the progression of AD
  • Cholinergic neurons: nerve cells in the brain that use ACh as their primary neurotransmitter; these neurons are particularly affected in AD

How It Works

  • In MG, the immune system produces autoantibodies that target and destroy AChRs at the neuromuscular junction
    • This reduces the number of available AChRs, impairing the transmission of signals from nerves to muscles
    • As a result, muscles become weak and fatigued, leading to the characteristic symptoms of MG
  • The exact cause of MG is unknown, but genetic and environmental factors may play a role in triggering the autoimmune response
  • In AD, the accumulation of beta-amyloid plaques and neurofibrillary tangles in the brain leads to the dysfunction and death of neurons
    • Beta-amyloid plaques form when beta-amyloid protein fragments clump together, disrupting communication between neurons and triggering inflammation
    • Neurofibrillary tangles form when tau protein becomes abnormally phosphorylated and aggregates inside neurons, interfering with their normal function
  • The loss of cholinergic neurons in AD contributes to cognitive decline and memory loss, as ACh is essential for learning and memory processes
  • The exact cause of AD is not fully understood, but a combination of genetic, lifestyle, and environmental factors is thought to contribute to its development

Spotting the Signs

  • MG symptoms may include:
    • Drooping eyelids (ptosis)
    • Double vision (diplopia)
    • Difficulty speaking (dysarthria) or swallowing (dysphagia)
    • Weakness in the arms and legs, particularly in proximal muscles (those closest to the body)
    • Fatigue that worsens with activity and improves with rest
  • Symptoms of MG can vary in severity and may fluctuate over time
  • AD symptoms typically develop gradually and worsen over time, progressing through mild, moderate, and severe stages
  • Early signs of AD may include:
    • Difficulty remembering recent events or conversations
    • Trouble finding the right words or following conversations
    • Misplacing items or getting lost in familiar places
    • Changes in mood, behavior, or personality
  • As AD progresses, symptoms may include:
    • Significant memory loss, including forgetting important events, names, and faces
    • Difficulty performing familiar tasks or learning new information
    • Confusion about time, place, or people
    • Impaired judgment and decision-making
    • Withdrawal from social activities or hobbies

Treatment Gameplan

  • Treatment for MG aims to improve muscle strength, reduce symptoms, and prevent complications
  • Cholinesterase inhibitors (pyridostigmine) are the first-line treatment for MG
    • These medications increase the availability of ACh at the neuromuscular junction, enhancing muscle strength
  • Immunosuppressants (prednisone, azathioprine, mycophenolate mofetil) may be used to suppress the immune system and reduce the production of autoantibodies
  • Plasmapheresis and intravenous immunoglobulin (IVIG) can be used for short-term symptom control in severe cases or before surgery
  • Thymectomy (surgical removal of the thymus gland) may be recommended for patients with thymic abnormalities
  • Treatment for AD focuses on managing symptoms, slowing disease progression, and providing support for patients and caregivers
  • Cholinesterase inhibitors (donepezil, rivastigmine, galantamine) are used to increase ACh levels in the brain, temporarily improving cognitive function
  • Memantine, an NMDA receptor antagonist, may be used in moderate to severe AD to help slow cognitive decline
  • Non-pharmacological interventions, such as cognitive stimulation, exercise, and social engagement, can help maintain cognitive function and quality of life

Meds to Know

  • Pyridostigmine (Mestinon): a cholinesterase inhibitor used as the first-line treatment for MG
    • Increases the availability of ACh at the neuromuscular junction, improving muscle strength
    • Side effects may include diarrhea, abdominal cramps, and increased secretions
  • Prednisone: an immunosuppressant corticosteroid used to reduce inflammation and suppress the immune system in MG
    • Helps decrease the production of autoantibodies targeting AChRs
    • Side effects may include weight gain, mood changes, and increased risk of infections
  • Azathioprine (Imuran) and mycophenolate mofetil (CellCept): immunosuppressants used as steroid-sparing agents in MG
    • Help maintain symptom control while reducing the need for high-dose corticosteroids
    • Side effects may include gastrointestinal disturbances, increased risk of infections, and liver function abnormalities
  • Donepezil (Aricept), rivastigmine (Exelon), and galantamine (Razadyne): cholinesterase inhibitors used to treat mild to moderate AD
    • Increase ACh levels in the brain, temporarily improving cognitive function and reducing symptoms
    • Side effects may include nausea, vomiting, diarrhea, and loss of appetite
  • Memantine (Namenda): an NMDA receptor antagonist used to treat moderate to severe AD
    • Helps slow cognitive decline by regulating glutamate activity in the brain
    • Side effects may include dizziness, headache, and constipation

Nursing Know-How

  • Assess patients with MG for signs of respiratory distress, such as difficulty breathing or swallowing, and monitor vital signs closely
  • Encourage patients to take frequent rest periods and conserve energy during activities
  • Educate patients and caregivers about the importance of medication adherence and proper administration techniques
  • Monitor for side effects of medications and report any adverse reactions to the healthcare team
  • Assist patients with AD in maintaining a safe and familiar environment to reduce confusion and agitation
  • Encourage patients to engage in cognitive stimulation activities, such as puzzles, games, and reminiscence therapy
  • Provide support and education to caregivers, emphasizing the importance of self-care and stress management
  • Collaborate with the interdisciplinary team to develop individualized care plans that address the unique needs of each patient

Watch Out For

  • Myasthenic crisis: a life-threatening complication of MG characterized by severe weakness of the respiratory muscles
    • Requires prompt recognition and management, including respiratory support and intensive care
  • Cholinergic crisis: an overdose of cholinesterase inhibitors, leading to excessive ACh activity and symptoms such as muscle weakness, sweating, and bradycardia
    • Treated by discontinuing the medication and providing supportive care
  • Adverse reactions to immunosuppressants, such as increased risk of infections, liver or kidney dysfunction, and bone marrow suppression
  • Behavioral and psychological symptoms of dementia (BPSD) in AD, such as agitation, aggression, and wandering
    • May require non-pharmacological interventions and careful use of antipsychotic medications when necessary
  • Caregiver burnout and stress, which can negatively impact the well-being of both the caregiver and the patient with AD
    • Encourage caregivers to seek support, respite care, and resources to manage the challenges of caregiving


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© 2024 Fiveable Inc. All rights reserved.
AP® and SAT® are trademarks registered by the College Board, which is not affiliated with, and does not endorse this website.