Ppt chapter 20

Chapter 20
Drugs Affecting Muscle Spasm
and Spasticity
Copyright © 2012 Wolters Kluwer Health | Lippincott Williams & Wilkins

Physiology
• The human body contains approximately 600 skeletal
muscles.
• Skeletal muscle movement is voluntary.
• Striated muscle is composed of two contractile proteins.
• Muscle contraction is triggered by a sudden inflow of
calcium ions (Ca2+).
• In the resting state, the protein tropomyosin winds
around actin and covers the myosin-binding sites.
• Muscle contraction stops when Ca2+ is removed from the
immediate environment of the myofilaments.

Muscle Fibers

Pathophysiology
• Muscle spasm
– A muscle spasm is a sudden, violent involuntary
contraction of a muscle or group of muscles.
– Spasms are related to a localized skeletal muscle
injury or an imbalance in electrolytes.
– Tonic spasm is characterized by an unusually
prolonged and strong muscular contraction.

Pathophysiology (cont.)
• Spasticity
– Spasticity is a condition in which certain muscles are
continuously contracted.
– This contraction causes stiffness or tightness of the
muscles.
– Spasticity may be associated with spinal cord injury.

Centrally Acting Muscle Relaxants
• They act in the central nervous system (CNS).
• Prototype drug: cyclobenzaprine (Flexeril)

Cyclobenzaprine: Core Drug Knowledge
• Pharmacotherapeutics
– Manages muscle spasms associated with acute
musculoskeletal disorders
• Pharmacokinetics
– Administered: oral. Metabolism: liver. Excreted:
urine and bile. Onset: 1 hour. Duration: 12 to 24
hours.
• Pharmacodynamics
– Relieves muscle spasms through a central action

Cyclobenzaprine: Core Drug Knowledge
(cont.)
• Contraindications and precautions
– Hyperthyroidism
– 14 days within use of MAOIs
• Adverse effects
– CNS depression and anticholinergic activity
– Arrhythmias, seizures, and MIs
• Drug interactions
– Tramadol, guanethidine, MAOIs, histamine-1
blocking agents, and various herbal remedies

Cyclobenzaprine: Core Patient Variables
• Health status
– Assess past medical history and drug allergies.
• Life span and gender
– Pregnancy Category B drug
– Use precaution in administration to the elderly.
• Lifestyle, diet, and habits
– Avoid alcohol and other CNS depressant use.
• Environment
– Assess the environment where the drug will be given.

Cyclobenzaprine: Nursing Diagnoses and
Outcomes
• Risk for Injury related to CNS depressant effects and
potential cardiovascular effects.
– Desired outcome: The patient will remain free from
injury throughout therapy.

Cyclobenzaprine: Planning and
Interventions
• Maximizing therapeutic effects
– Take with full glass of water at evenly spaced
intervals.
– Coordinate physical therapies with administration.
• Minimizing adverse effects
– Assess for excessive sedation.
– Caution the patient about the potential for orthostatic
hypotension.

Cyclobenzaprine: Teaching, Assessment,
and Evaluation
• Patient and family education
– Take medication as prescribed.
– Explain adverse effects.
– Do not take with other OTC medications.
• Ongoing assessment and evaluation
– Evaluate the patient’s safety.
– Monitor the level of sedation.

Question
• Cyclobenzaprine is chemically similar to which of the
following drugs?
– A. Adrenergic agents
– B. Benzodiazepines
– C. Tricyclic antidepressants
– D. MAOIs

Answer
• C. Tricyclic antidepressants
• Rationale: Cyclobenzaprine is structurally similar to
the tricyclic antidepressants.

Centrally Acting Spasmolytics
• The centrally acting spasmolytics work in the CNS to
reduce excessive reflex activity.
• Allow muscle relaxation
• Prototype drug: baclofen (Lioresal)

Baclofen: Core Drug Knowledge
– Relieves some components of spinal spasticity
– Administered: oral. Distribution: crosses blood–brain
barrier. Metabolism: liver. Excreted: urine and bile.
Peaks: 2 to 3 hours
– Acts specifically at the spinal end of the upper motor
neurons at GABAB receptors to cause
hyperpolarization

Baclofen: Core Drug Knowledge (cont.)
– Hypersensitivity and spasticity of cerebral origin
• Adverse effects
– Drowsiness, weakness, dizziness and light-headedness,
headache, nausea and vomiting,
hypotension, constipation, lethargy and fatigue,
confusion, insomnia, and increased urinary frequency
– CNS depressants or TCAs

Baclofen: Core Patient Variables
• Health status
– Assess past medical history and allergies.
– Perform physical assessment.
– Older patients are more susceptible to sedation.
– Caution the patient about the concurrent use of
alcohol.
• Environment
– Assess the environment where the drug will be given.
It is usually given at the home.

Baclofen: Nursing Diagnoses and
Outcomes
• Acute Pain related to headache, muscle pain, GI
disturbances, or rash
– Desired outcome: The patient will be provided with
measures to decrease the discomfort of drug therapy
and the possibility of nonadherence.
• Risk for Disturbed Sensory Perception related to visual
changes, vestibular dysfunction, and somatosensory
changes
– Desired outcome: The patient will be protected
from injury if dizziness, weakness, visual changes, or
perceptual changes occur.

Baclofen: Planning and Interventions
– Take with full glass of water at evenly spaced
intervals.
– If GI distress occurs, coordinate with meals.
– Ensure patient safety.
– Do not abruptly stop the medication.

Baclofen: Teaching, Assessment, and
Evaluation
– Teach the importance of patient safety.
– Caution the patient about the concurrent use of
alcohol.
– Monitor for the emergence of hallucinations or
psychotic episodes.
– Assess for improved symptoms of spasticity.

Question
• Baclofen therapy is effective at treating muscle spasms
due to a cerebral vascular accident.
– A. True
– B. False

Answer
• B. False
• Rationale: Baclofen therapy does not affect skeletal
muscle spasms resulting from CVA or parkinsonism.
Baclofen does not treat this condition because of the
mechanism of action of the drug.

Peripherally Acting Spasmolytics
• Peripherally acting spasmolytics relax muscles through
direct action on the skeletal muscle fibers.
• They do not interfere with neuromuscular
communication.
• They have no CNS effects.
• Prototype drug: dantrolene (Dantrium)

Dantrolene: Core Drug Knowledge
– Used to treat malignant hyperthermia
– Administered: oral or IV. Metabolism: liver. Excreted:
kidneys. Peak: 5 hours. T½: 7.3 hours
– Reduces the amount of Ca2+ released from the
sarcoplasmic reticulum, thereby relaxing the muscle

Dantrolene: Core Drug Knowledge (cont.)
– Liver disease
• Adverse effects
– Muscle weakness, fatal hepatitis, seizures, and pleural
effusion with pericarditis
– CNS depressants, clofibrate, estrogens, verapamil,
and warfarin

Dantrolene: Core Patient Variables
• Health status
– Assess past medical and physical assessment.
– Consider the age before administration.
– Assess for lactose intolerance.
• Environment
– Can cause photosensitivity

Dantrolene: Nursing Diagnoses and
Outcomes
• Risk for Injury related to muscular weakness
– Desired outcome: The patient will be injury free
despite muscular weakness.
• Risk for diarrhea or constipation related to drug effects
– Desired outcome: The patient will maintain
baseline bowel habits.

Dantrolene: Nursing Diagnoses and
Outcomes (cont.)
• Risk for Disturbed Sensory Perception: Kinesthetic
related to dizziness, malaise, and fatigue
– Desired outcome: The patient will remain free of
injury from adverse effects.
• Disturbed Body Image related to drug-related
dermatologic effects
– Desired outcome: Any adverse effects will be
resolved by the end of therapy.

Dantrolene: Planning and Interventions
– Administer with food or milk to avoid gastric distress.
– Do not crush extended release capsules.
– Provide for patient safety.
– Advise the use of sunscreen.
– Titrate dose to maximum effectiveness.

Dantrolene: Teaching, Assessment, and
Evaluation
– Explain why the drug is prescribed.
– Discuss adverse effects of the drug.
– Monitor for improvement in symptoms of spasticity
and decrease in resistance to passive movement.
– Monitor for adverse effects.

Question
• Dantrolene is used to treat which of the following
condition(s)?
– A. Hypertensive crisis
– B. Malignant hyperthermia
– C. Pain associated with lumbar stenosis
– D. All of the above

Answer
• B. Malignant hyperthermia
• Rationale: IV dantrolene is the drug of choice for
acute treatment of malignant hyperthermia.
Preoperatively, it can be used orally or intravenously
to prevent malignant hyperthermia in patients
considered at risk.

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