pharm: neuromuscular agents

what is myasthenia gravis

myasthenia gravis = autoimmune disorder where antibodies obstruct binding of ACH and destroy receptor sites which blocks binding of ACH

s/s of myasthenia gravis

skeletal muscle weakness, fatigue, ptosis, dysphagia/dysarthria, respiratory muscle weakness

myasthenic crisis

inadequate acetylcholinesterase inhibitor medications; too little ACH

cholinergic crisis

too much acetylcholinesterase medications; too much ACH

myasthenic crisis triggers

inadequate dosing/missed doses, emotional stress, infection

cholinergic crisis triggers

occurs within 30 to 60 minutes after overdose of MG medications

sx of myasthenic crisis and cholinergic crisis

SAME; muscle weakness, respiratory paralysis, dysphagia

what are the other sx for cholinergic crisis

increased salivation, sweating, bronchial secretions, miosis (pupil constriction), bradycardia

whats important to know about AChE inhibitors medications

administered on TIME because late can cause muscle weakness

what do acetylcholinesterase inhibitors do?

MOA: block enzyme that breaks down ACH, increase amount of ACH available which increases muscle contraction and strength in myasthenia gravis pt

Edrophonium Chloride (Tensilon)

MOA: ACHase inhibitor; often used to diagnose myasthenia gravis. helps to differentiate myasthenia crisis and cholinergic crisis

Edrophonium Chloride (Tensilon) considerations

ultrashort acting (5-20 minutes duration); if ptosis is improved diagnosis is likely myasthenia gravis or myasthenic crisis

Pyridostigmine Bromide (Mestinon)

MOA: ACHase; used to maintenance of myasthenia gravis and used long term.

- given every 3-6 hours PO!

Pyridostigmine Bromide (Mestinon) side effects

increased salivation, tearing, miosis (constriction), blurred vision, bradycardia/hypoTN, GI distress

how does neostigmine help as a AChE inhibitor

can be given IV or IM for urgent treatment but shorter half life than pyridostigmine

- can be used after determining client has a myasthetic crisis

what are nursing interventions for AChE inhibitors

administer doses on time, take drug before meals, have antidote available for cholinergic crisis, encourage pt to wear medical identification

what is the antidote for cholinergic crisis ?

anticholinergic !! --> atropine!

what is multiple sclerosis?

autoimmune disorder that destroys myelin sheath of neurons in CNS

sx of MS

generalized weakness, blurred vision/diplopia, weakness

how do we treat MS?

immunomodulators and immunosppressants

Beta-Interferon (Avonex, Rebif)

MOA: immunomodulators; suppresses inflammatory response and controls secretion of pro-inflammatory and anti-inflammatory cytokines = suppresses T-cell activation

Beta-Interferon (Avonex, Rebif) considerations

administered IM once a week, self-injection pen

will slow disease progression and prevent relapses/exacerbations of disease

Beta-Interferon (Avonex, Rebif) side effects

SOB, chest pain, edema, depression, suicidal ideation, neutropenia

Methylprednisolone (Solu-Medrol)

MOA: immunosuppressants; steroid that helps to treat acute inflammation and for acute exacerbations of MS

what do skeletal muscle relaxants do

relieves muscle spasms (uncontrollable contraction of muscle) and spasticity (constant state of tension)

Methocarbamol (Robaxin)

MOA: CNS depressant and sedative; skeletal relaxation is thought to happen due to overall CNS depression

Methocarbamol (Robaxin) considerations

PO, IM, IV routes

Methocarbamol (Robaxin) side effects

dizziness, sleepyness (somnolence), lightheadedness, N/V

- DO NOT give in pregnancy

Cyclobenzaprine HCL

MOA: centrally acting muscle relaxant; suppresses hyperactive reflexes and muscle spasms that do not respond to anti-inflammatory agents or therapy

Cyclobenzaprine HCL considerations

no action on the NMJ or the muscles involved

Cyclobenzaprine HCL side effects

anticholinergic side effects, sedation, angioedema, seizures, myocardial infarction

Baclofen (lioresal) pumps

Central acting muscle relaxants; used for muscle spasms caused by MS and spinal cord injury; goal is to improve muscle tone and decrease in frequency/severity of muscle spasms

what are interactions with central acting muscle relaxants

do not take with any other CNS depressants (avoid alcohol, driving, and operating machinery)

what is contraindicated with central acting muscle relaxants

do not use with renal or liver diseases

what is a risk and teaching point with central acting muscle relaxants

dependence risk; for acute spasms should be taken for no longer than 3 weeks

- teach pt not to stop abruptly; taper off

- use cautiously when pregnant or breastfeeding