muscle relaxants

SKELETAL MUSCLE RELAXANTS

DRUG NAME CLASS

  • Centrally-acting muscle relaxants
    • baclofen (Lioresal)
    • carisoprodol (Soma)
    • chlorzoxazone (Parafon)
    • cyclobenzaprine (Amrix, Flexeril)
    • metaxalone (Skelaxin)
    • methocarbamol (Robaxin)
    • tizanidine (Zanaflex)
    • orphenadrine (Norflex)
  • Direct-acting muscle relaxants
    • dantrolene (Dantrium)

MECHANISM OF ACTION

  • Centrally-acting muscle relaxants: Interfere with muscle reflexes in the central nervous system to decrease skeletal muscle tone.
  • Direct-acting muscle relaxants: Prevent the release of calcium ions from the sarcoplasmic reticulum of skeletal muscle cells to reduce muscle contraction.

INDICATIONS

  • Muscle spasms and spasticity
  • Spasticity
  • Malignant hyperthermia

ROUTE(S) OF ADMINISTRATION

  • Centrally-acting muscle relaxants:
    • PO (Oral)
    • IV (Intravenous)
    • IM (Intramuscular) [specifically for methocarbamol]
    • Intrathecal (specifically for baclofen)
  • Direct-acting muscle relaxants:
    • PO
    • IV

SIDE EFFECTS

  • Drowsiness
  • Dizziness
  • Headaches
  • Excessive weakness
  • Anorexia
  • Nausea
  • Vomiting
  • Constipation
  • Hypotension
  • Arrhythmias
  • Urinary frequency and urgency
  • Specific adverse effects:
    • Orphenadrine: Atropine-like side effects
    • Chlorzoxazone: Orange or purplish-red discoloration of urine
    • Baclofen: Hyporeflexia, hypothermia, bradycardia, tolerance, and dependence.

CONTRAINDICATIONS AND CAUTIONS

  • Severe hepatic or renal disease
  • Combination with CNS depressants (e.g., barbiturates, opioids, tricyclic antidepressants, alcohol)
  • Use with caution in:
    • Pregnancy
    • Breastfeeding
    • Seizure disorders
    • Heart disease

NURSING CONSIDERATIONS

ASSESSMENT AND MONITORING
  • Focused assessment:
    • Pain and mobility
  • Diagnostic test results:
    • X-ray
    • CT (Computed Tomography)
    • MRI (Magnetic Resonance Imaging)
  • Laboratory tests:
    • Complete Blood Count (CBC)
    • Liver function tests
    • Renal function tests
  • Monitor for side effects and CNS, liver toxicity
  • Specifically for intrathecal baclofen: monitor the insertion site for infection.

CLIENT EDUCATION

  • Encourage other therapies such as rest, heat, massage, and physical therapy.
  • Instruct to take the medication as directed:
    • With a glass of water
    • With food or milk if gastric upset occurs
  • Manage side effects:
    • Dizziness: Advise changing positions slowly.
    • Drowsiness: Advise avoiding activities that require alertness and avoiding other CNS depressants.
    • Effects such as dry mouth, blurred vision, tachycardia, urinary retention, and constipation may occur; cyclobenzaprine may cause visual hallucinations and anticholinergic effects.
    • Warning signs of overdose: Increased drowsiness and low muscle tone.
    • For dry mouth: Suggest sugar-free chewing gum or lozenges, as well as frequent sips of water.
    • For constipation: Recommend increasing fiber and fluid intake.
    • For urinary retention: Advise emptying the bladder regularly.
  • Report symptoms of liver damage: Nausea, fatigue, or anorexia.
  • Report symptoms of cardiac arrhythmias: Palpitations, or feeling a fast heartbeat.
  • For those with a baclofen implanted pump:
    • Warning signs of insufficient medication: Sudden return of spasticity, auditory or visual hallucinations.
  • Regular visits to healthcare providers are necessary to ensure that equipment is in good working order and for medication refills.