Myasthenia Gravis and Alzheimers Drugs

Myasthenia Gravis (MG)

Autoimmune disorder that causes ACh receptor destruction

• Impaired ACh binding – reduced muscle contraction​

• Causes muscle weakness, fatigue ptosis (droopy eyelids​), dysphagia, respiratory weakness, and diploplia (seeing double​)

• Symptoms worsen with more activity bc the amount of ACH available gets depleted with activity​

• Diagnostics - Antibody tests, EMG, nerve stimulation, CT/MRI (thyoma)​

Myasthenic vs Cholinergic Crisis

Myasthenic

• Too little ACh

• Respiratory distress/failure bc not enough ACh

Cholinergic crisis​

• Too much ACh​

• Similar respiratory distress​

• Antidote: atropine

if ACh defeciency and you give them meds, they will get better, if they have too much ach and you give them meds, they will get worse​

Myasthenia Gravis Drugs

AChE inhibitors

• Pyridostigmine

• Neostigmine

Pyridostigmine

AChE inhibitor - ↑ ACh

• MoA: Causes reversible inhibition of AChE within the synapse, allowing more ACh to bind to cholinergic receptors and prolonging its effects

• Indication: Management of MG symptoms

• Contraindication: obstruction of the intestine or urinary tract

• Interactions: Atropine

• Give AChE inhibtiors 30-60 min before meals​

Adverse Effects of Pyridostigmine

• Excess salivation

• Increased urination

• Diaphoresis

• N/V/D

• Bradycardia

• Decrease in cardiac output

• Bronchospasms

• Dysphagia

• Dysarthria

• Hoarseness

• Seizures

• Weakness skeletal muscles

Nursing Considerations for Pyridostigmine

• Give AChE inhibtiors 30-60 min before meals​

• Monitor resps and swallowing​

• Teach difference between myasthenic vs cholinergic criss​

• Encourage medical alert ID​

Alzheimer’s Disease

Progressive neurodegenerative disorder

• Causes memory loss, confusion

• β-amyloid plaques & tau tangles damage neurons, leading to neuronal death

• decreases ACh in hippocampus

• Stages: early memory loss -> dependence -> total care​

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Alzheimer’s Drugs

Improves cognition; slows decline, not curative.​

• AChE inhibitors

  • Donepezil

  • Rivastigmine

  • Galantamine

• NMDA blockers

  • Memantine

Donepezil

AChE inhibitor

• MoA: Causes reversible inhibition of AChE

• Indications: Mild to severe Alzheimer’s disease, overdose of atropine

• Contraindications: peptic ulcer disease, Active GI bleeding, Urinary or intestinal obstruction

• Interactions: Anticholinergic agents

• Give at bedtime

Adverse Effects of Donepezil

• Dizziness

• Bradycardia

• GI upset​

• Fatigue

• Headache

• Bronchoconstriction

Nursing Considerations for Donepezil

• Give at bedtime to avoid dizziness and bradycardia in day​

• Monitor safety​

• Stop meds if heart block occurs or severe bradycardia​

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Memantine - MoA, Indication, Adverse Effects

NMDA blocker

• MoA: Prevents calcium overload and neuronal death

• Indication: When combined with donepezil, can be used for moderate to severe alzheimers​

• Adverse Effects:

  • Diarrhea/constipation

  • Dizziness

  • Headache

  • Confusion

  • Pancreatitis

  • Hepatitis

  • Stevens–Johnson syndrome