ppt chapter 20
TRANSCRIPT
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Chapter 20
Drugs Affecting Muscle Spasm and Spasticity
Chapter 20
Drugs Affecting Muscle Spasm and Spasticity
Copyright © 2012 Wolters Kluwer Health | Lippincott Williams & Wilkins
Physiology 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.
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Muscle FibersMuscle Fibers
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Pathophysiology 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.
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Pathophysiology (cont.)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.
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Centrally Acting Muscle Relaxants Centrally Acting Muscle Relaxants
• They act in the central nervous system (CNS).
• Prototype drug: cyclobenzaprine (Flexeril)
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Cyclobenzaprine: Core Drug Knowledge 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
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Cyclobenzaprine: Core Drug Knowledge(cont.) 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
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Cyclobenzaprine: Core Patient Variables 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.
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Cyclobenzaprine: Nursing Diagnoses and Outcomes 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.
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Cyclobenzaprine: Planning and InterventionsCyclobenzaprine: 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.
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Cyclobenzaprine: Teaching, Assessment, and EvaluationCyclobenzaprine: 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.
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QuestionQuestion
• Cyclobenzaprine is chemically similar to which of the following drugs?
– A. Adrenergic agents
– B. Benzodiazepines
– C. Tricyclic antidepressants
– D. MAOIs
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AnswerAnswer
• C. Tricyclic antidepressants
• Rationale: Cyclobenzaprine is structurally similar to the tricyclic antidepressants.
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Centrally Acting Spasmolytics Centrally Acting Spasmolytics
• The centrally acting spasmolytics work in the CNS to reduce excessive reflex activity.
• Allow muscle relaxation
• Prototype drug: baclofen (Lioresal)
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Baclofen: Core Drug Knowledge Baclofen: Core Drug Knowledge
• Pharmacotherapeutics
– Relieves some components of spinal spasticity
• Pharmacokinetics
– Administered: oral. Distribution: crosses blood–brain barrier. Metabolism: liver. Excreted: urine and bile. Peaks: 2 to 3 hours
• Pharmacodynamics
– Acts specifically at the spinal end of the upper motor neurons at GABAB receptors to cause hyperpolarization
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Baclofen: Core Drug Knowledge (cont.)Baclofen: Core Drug Knowledge (cont.)
• Contraindications and precautions
– 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
• Drug interactions
– CNS depressants or TCAs
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Baclofen: Core Patient Variables Baclofen: Core Patient Variables • Health status
– Assess past medical history and allergies.
– Perform physical assessment.
• Life span and gender
– Older patients are more susceptible to sedation.
• Lifestyle, diet, and habits
– 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.
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Baclofen: Nursing Diagnoses and Outcomes 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.
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Baclofen: Planning and InterventionsBaclofen: Planning and Interventions
• Maximizing therapeutic effects
– Take with full glass of water at evenly spaced intervals.
– If GI distress occurs, coordinate with meals.
• Minimizing adverse effects
– Ensure patient safety.
– Do not abruptly stop the medication.
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Baclofen: Teaching, Assessment, and EvaluationBaclofen: Teaching, Assessment, and Evaluation
• Patient and family education
– Teach the importance of patient safety.
– Caution the patient about the concurrent use of alcohol.
• Ongoing assessment and evaluation
– Monitor for the emergence of hallucinations or psychotic episodes.
– Assess for improved symptoms of spasticity.
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QuestionQuestion
• Baclofen therapy is effective at treating muscle spasms due to a cerebral vascular accident.
– A. True
– B. False
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AnswerAnswer
• 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.
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Peripherally Acting Spasmolytics 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)
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Dantrolene: Core Drug Knowledge Dantrolene: Core Drug Knowledge
• Pharmacotherapeutics
– Used to treat malignant hyperthermia
• Pharmacokinetics
– Administered: oral or IV. Metabolism: liver. Excreted: kidneys. Peak: 5 hours. T½: 7.3 hours
• Pharmacodynamics
– Reduces the amount of Ca2+ released from the sarcoplasmic reticulum, thereby relaxing the muscle
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Dantrolene: Core Drug Knowledge (cont.)Dantrolene: Core Drug Knowledge (cont.)
• Contraindications and precautions
– Liver disease
• Adverse effects
– Muscle weakness, fatal hepatitis, seizures, and pleural effusion with pericarditis
• Drug interactions
– CNS depressants, clofibrate, estrogens, verapamil, and warfarin
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Dantrolene: Core Patient Variables Dantrolene: Core Patient Variables
• Health status
– Assess past medical and physical assessment.
• Life span and gender
– Consider the age before administration.
• Lifestyle, diet, and habits
– Assess for lactose intolerance.
• Environment
– Can cause photosensitivity
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Dantrolene: Nursing Diagnoses and Outcomes 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.
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Dantrolene: Nursing Diagnoses and Outcomes (cont.)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.
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Dantrolene: Planning and InterventionsDantrolene: Planning and Interventions
• Maximizing therapeutic effects
– Administer with food or milk to avoid gastric distress.
– Do not crush extended release capsules.
• Minimizing adverse effects
– Provide for patient safety.
– Advise the use of sunscreen.
– Titrate dose to maximum effectiveness.
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Dantrolene: Teaching, Assessment, and EvaluationDantrolene: Teaching, Assessment, and Evaluation
• Patient and family education
– Explain why the drug is prescribed.
– Discuss adverse effects of the drug.
• Ongoing assessment and evaluation
– Monitor for improvement in symptoms of spasticity and decrease in resistance to passive movement.
– Monitor for adverse effects.
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QuestionQuestion
• 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
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AnswerAnswer
• 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.