Skeletal Muscle Relxants

SKELETAL MUSCLE RELAXANTS Movement & control of muscles regulated by:  Spinal reflexes  Cerebral cortex  Cerebellum  Basal ganglia Spinal reflexes • Simple  incoming sensory neuron & an outgoing motor neuron. • Complex  plus interneurons Neuromuscular Abnormalities: 1. Muscle Spasm  often results from injury to musculoskeletal system. • overstretch muscle • tear in ligament or tendon 2. Muscle Spasticity  often results from damage to neurons within CNS.  permanent condition  due to increase muscle excitation or decrease inhibition within CNS  muscle hyperactivity • cerebral palsy • paraplegia SKELETAL MUSCLE RELAXANTS • decrease muscle tone & movements by reducing skeletal muscle activity. Classification: I.

Centrally Acting skeletal muscle relaxants 1. baclofen (Lioresal) 2. carisoprodol (Soma) 3. chlorphenesin (Maolate) 4. chlorzoxazone (Paraflex) 5. cyclobenzaprine ( Flexeril) 6. metaxalone (Skelaxin) 7. methocarbamol (Robaxin) 8. orphenadrine (Banflex, Norflex) 9. tizanidine (Zanaflex)

II.

Direct-Acting skeletal muscle relaxants 1. dantrolene (Dantrium) 2. botulinum toxin type B (Myobloc) 3. botulinm toxin type A (Botox Cosmetic)

III.

Peripheral Acting skeletal muscle relaxants 1. atracurium (Tracium) 2. pancuronium (Pavulon) 3. rocuronium (Zemuron) 4. vecuronium (Norcuron) 5. tubocurarine 6. succinylcholine (Anectin, Quelicin)

I. Centrally acting skeletal muscle relaxants  act on CNS  block reflexes in CNS that cause muscle spasm  causing muscle relaxation.  Indications: 1. relief of discomfort/pain of acute musculoskeletal conditions. 2. tx of muscle spasticity & pain in spinal cord injury  SE/ Adverse effects: 1. CNS: drowsiness,dizziness, headache, ataxia, confusion 2. GI: nausea, dry mouth, anorexia, constipation Nursing Responsibities; Before administration: • Assess extent of muscle spasm, spasticity, pain & ROM. • Perform a baseline mental status examination. • Note hx of seizures. • Be aware of contraindications: o Hypersensitivity o Skeletal muscle spasms from rheumatic disorders • Be cautious in: o Hx of epilepsy o Cardiace dysfunction o Muscle weakness o Renal or hepatic dysfunction o Pregnancy / lactation. During/ After • Taken with food to decrease GI upset. • Provide additional measures to relieve discomfort. • Ensure client safety. • Discontinue drug for any sign of hypersensitivity or liver dysfunction. • Monitor respiratory status & muscle responses. • Monitor liver enzymes. • Observe for CNS side effects. • Client teachings: o Avoid alcohol & CNS depressants. o Not to drive or operate machineries. o Not to abruptly stop drug intake.

1. baclofen (Lioresal) • Tx of muscle spasticity assoc. with NM dses. & spinal cord injuries • taper slowly • use cautiously in pxs whose spasticity contributes to mobility, posture or balance 2. carisoprodol (Soma) • Tx of muscle spasms in acute musculoskeletal conditions. • safer in older pxs & those with renal & hepatic dysfunctions 3. chlorphenesin ( (Maolate) 4. chlorzoxazone (Paraflex) 5. cyclobenzaprine (Flexeril) • Tx of acute or severe muscle spasms. 6. metaxalone (Skelaxin) • Tx of acute or severe muscle spasms in children >12 yo. • have an established pediatric dose 7. methocarbamol (Robaxin) • Tx of acute or severe muscle spasms. • Tx of signs & sxs of tetanus. 8. orphenadrine (Banflex) • Tx of actue or severe muscle spasms. • Relief of quinidine –induced leg cramps. • can be toxic at mild overdose. 9. tizanidine (Zanaflex) • Tx of acute or severe muscle spasticity 10. diazepam (Valium) • DOC for pxs with severe muscle spasm & pain precipitated by anxiety. II. Direct Acting skeletal muscle relaxants • acts directly within skeletal muscle fiber. 1. dantrolene (Dantrium) • indications: 1. Tx of muscle spasticity in chronic neurologic disorders 2. Prevent malignant hyperthermia. • Embryotoxic in animals • Contraindications: o spasticity that contributes to locomotion, upright position or increased function. o active hepatic dse. o lactation & pregnancy.

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Caution in: o Women & pxs older than 35 yo o Hx of liver dse. o COPD o Cardiac dse

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Adverse effects: 1. CNS depression 2. GI disturbances 3. Direct hepatocellular damage & hepatitis 4. urinary frequency, enuresis & dysuria 5. acne, abnormal hair growth 6. photosensitivity

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Dantrolene + estrogen  increase incidence of liver toxicity.

2. botulinum toxin B (Myobloc) • reduce severity of abnormal head position & pain in cervical dystonia. 3. botulinum toxin A (Botox Cosmetic) • improve appearance of frown lines bw eyebrows. • repeated every 3 months • adverse effects: headache, resp. infxns, flu-like syndrome & droopy eyelids. III. Peripheral acting skeletal muscle relaxants •

interfere with nerve impulses bw the motor end plate & skeletal muscle receptors.

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blocks depolarization/ repolarization in skel. Muscles  muscle paralysis.

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Indications: 1. Adjunct to general anesthesia 2. relaxation of skeletal muscles during surgery, ET intubation, mechanical ventilation.

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Adverse effects: 1. respiratory depression 2. muscle weakness 3. cardiac arrhythmias, cardiac arrest & hypotension.