Chapter 29Agents Used to Treat

Musculoskeletal Health Alterations

Skeletal Muscle

Also called striated muscle; is attached to the skeleton

Contraction is under voluntary control

Contraction controlled by the nervous system

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Agents: Musculoskeletal Disorders

Nerve impulses travel down the motor neurons of the nervous system Cause skeletal muscle contraction

The neuromuscular junction contains the terminal of a motor neuron and a muscle fiber

Motor axon terminals contain thousands of vesicles filled with acetylcholine

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Classes:Musculoskeletal Drugs

Neuromuscular blocking agentsCentrally acting skeletal muscle relaxants

Direct-acting skeletal muscle relaxants

Skeletal muscle stimulants

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Neuromuscular Blocking Agents

ActionBlock the action of acetylcholine

Mimic acetylcholine action and prevent cholinesterase from working; the muscle becomes overtired and the client is unable to use the muscle 5

Neuromuscular Blocking Agents

Relax or paralyze the skeletal muscles

Used for:SurgeryElectroconvulsive therapyEndotracheal intubationTetanus treatment

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Neuromuscular Blocking Agents

Used to relax one or more musclesNeuromuscular blockadeParalyze skeletal muscle groupsDoes not affect cardiac muscleTo assist intubation and mechanical

ventilationUsually administered IVClose monitoring requiredAntidotes should be readily available

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Neuromuscular Blocking Agents

Not useful for spasticity or rigidity of muscles caused by neurological disease or trauma

Many drug interactions

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Centrally Acting Skeletal Muscle Relaxants

Depress the CNS in the brainstem, basal ganglia, and neurons of the spinal cord

Do not act on the neuromuscular junction

Relieve pain associated with skeletal muscle spasms—cerebral palsy

High risk: sedation9

Centrally-acting musculoskeletal agents

Baclofen – PO (Kemstro), intrathecal (Lioresal)Spasticity from multiple sclerosis or spinal injury

Carisoprodol (Soma) – PO Metaxalone (Skelaxin) – PO

Should be taken with food

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Centrally-acting musculoskeletal agents

(cont’d)

Diazepam (Valium) – PO, IM, IVMay cause dependenceCannot be mixed in syringe with other drugs

Discontinue gradually to avoid withdrawal reactions

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Centrally Acting Skeletal Muscle Relaxants

Use cautiously with other CNS depressants

Administered orally or parenterally

Patients should be cautious when performing activities due to sedation

May cause dependence12

Direct-Acting Skeletal Muscle Relaxants

Inhibit calcium release from the skeletal muscles

Muscle is then less responsive to nerve impulsesDantrolene acts directly on skeletal muscle; relaxes spastic muscle

Used in the treatment of multiple sclerosis, cerebral palsy, spinal cord injury, and stroke

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Adverse EffectsDiarrheaGI upsetPhotosensitivityChanges in sensory perceptionInsomniaDepression HepatotoxicityHepatitis

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Myasthenia Gravis

Affects 1 in 20,000 peopleDevelopment of skeletal muscle weakness

Symptoms include drooping eyelids, difficulty swallowing, and inability to perform simple tasks

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Myasthenia Gravis

May be caused by damage to acetylcholine receptors at the neuromuscular junction

Autoimmune reactionTherapy is aimed at increasing the concentration of acetylcholine at the neuromuscular junction

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Myasthenia GravisNeostigmine (Prostigmin)Pyridostigmine bromide (Mestinon) – most popularly used for POLonger duration, better tolerated PO than neostigmine

Edrophonium (Tensilon, Reversol) – parenteral (IV) used for diagnosis or MG crisis

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Skeletal-Muscle Stimulants

Correct muscular weakness such as myasthenia gravis

Inhibits the action of anticholinesterase; more acetylcholine is available to cause and maintain the muscle contraction

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Skeletal-Muscle Stimulants

Side effects/adverse effectsCaused by unusual cholinergic activityIncreased salivationDiarrheaIntestinal crampingBradycardiaMiosis

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Myasthenia Gravis: Nursing Considerations

- assess muscle functioning with vital

signs - watch for symptoms of myasthenic

crisis - take medication before eating or

activity - plan activities after taking

medications - patients need to carry

identification of condition

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