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Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins
Muscle RelaxantsMuscle Relaxants
Chapter 25
Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins
Regulation of Movement and Control of Muscles
Regulation of Movement and Control of Muscles
• Spinal Reflexes
• Influences from Upper-level CNS Areas
– Basal ganglia
– Cerebellum
– Cerebral cortex
Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins
Types of Spinal ReflexesTypes of Spinal Reflexes
• Simple
– Involving an incoming sensory neuron and an outgoing motor neuron
• Complex
– Involving interneurons which communicate with the related centers in the brain
Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins
Reflex Arc Showing Pathway of ImpulsesReflex Arc Showing Pathway of Impulses
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Fibers in the CNS Controlling Different Types of Movements
Fibers in the CNS Controlling Different Types of Movements
• Pyramidal Tract
– Controls precise intentional movements
• Extrapyramidal Tract
– Modulates unconsciously controlled muscle activity
– Allows the body to make automatic adjustments in posture, position, and balance
Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins
Neuromuscular AbnormalitiesNeuromuscular Abnormalities
• Muscle Spasm
– Often results from injury to the musculoskeletal system
– Caused by the flood of sensory impulses coming to the spinal cord from the injured area
• Muscle Spasticity
– Result of damage to neurons within the CNS
– May result from an increase in excitatory influences or a decrease in inhibitory influences within the CNS
Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins
Action of Skeletal Muscle RelaxantsAction of Skeletal Muscle Relaxants
• Most Relaxants
– Work in the brain and spinal cord
– Interfere with cycle of muscle spasm and pain
• Botulinum Toxins and Dantrolene
– Enter muscle fibers directly
Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins
Action of Centrally Acting Skeletal Muscle Relaxants
Action of Centrally Acting Skeletal Muscle Relaxants
• Work in the upper levels of the CNS to interfere with the reflexes causing the muscle spasm
– Possible depression anticipated with their use
• Lyse or Destroy Spasm
– Often referred to as spasmolytics
Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins
QuestionQuestion
Which of the following may result in muscle spasticity?
A. A decrease in inhibitions
B. An increase in excitatory influences
C. An increase in inhibitory influences
D. A decrease in excitatory influences
Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins
AnswerAnswer
B. An increase in excitatory influences
Rationale: Muscle spasticity may result from an increase in excitatory influences or a decrease in inhibitory influences within the CNS.
Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins
Centrally-Acting Skeletal Muscle Relaxants
Centrally-Acting Skeletal Muscle Relaxants
• Actions
– Exact mechanism of action is not known
– Thought to involve action in the upper or spinal interneurons
• Indications
– Alleviation of signs and symptoms of spasticity; use in spinal cord injuries or diseases
• Pharmacokinetics
– Rapidly absorbed and metabolized in the liver
– Excreted in the urine
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Centrally-Acting Skeletal Muscle Relaxants (cont.)
Centrally-Acting Skeletal Muscle Relaxants (cont.)
• Contraindications
– Known allergy
– Rheumatic disorders
• Cautions
– Epilepsy
– Cardiac dysfunction
– Conditions marked by muscle weakness
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Centrally-Acting Skeletal Muscle Relaxants (cont.)
Centrally-Acting Skeletal Muscle Relaxants (cont.)
• Adverse Reactions
– Drowsiness
– Fatigue
– Weakness
– Confusion
– Headache
– Nausea
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Centrally-Acting Skeletal Muscle Relaxants (cont.)
Centrally-Acting Skeletal Muscle Relaxants (cont.)
• Adverse Reactions (cont.)
– Dry mouth
– Hypotension
• Drug-to-Drug Interactions
– CNS depressants
Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins
Direct-Acting Skeletal Muscle RelaxantsDirect-Acting Skeletal Muscle Relaxants
• Actions
– Interfering with the release of calcium from the muscle tubules
– This prevents the fibers from contracting
– Does not interfere with neuromuscular transmission
• Indications
– Treatment of spasticity directly affecting peripheral muscle contraction
– Management of spasticity associated with neuromuscular diseases
Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins
Direct-Acting Skeletal Muscle Relaxants (cont.)
Direct-Acting Skeletal Muscle Relaxants (cont.)
• Pharmacokinetics
– Slowly absorbed from the GI tract
– Metabolized in the liver
– T ½ 4-8 hours
– Excreted in the urine
• Contraindications
– Known allergy
– Spasticity
Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins
Direct-Acting Skeletal Muscle Relaxants (cont.)
Direct-Acting Skeletal Muscle Relaxants (cont.)
• Contraindications (cont.)
– Hepatic disease
– Lactation
• Cautions
– Women
– All patients older than 35 years
– Cardiac disease
Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins
Direct-Acting Skeletal Muscle Relaxants (cont.)
Direct-Acting Skeletal Muscle Relaxants (cont.)
• Adverse Reactions
– Fatigue
– Weakness
– Confusion
– GI irritation
– Enuresis
• Drug-to-Drug Interactions
– Estrogen
– Neuromuscular junction blockers
Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins
Mechanisms of Muscle RelaxantsMechanisms of Muscle Relaxants
Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins
Use of Muscle Relaxants Across the Lifespan
Use of Muscle Relaxants Across the Lifespan
Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins
Prototype Centrally Acting Skeletal Muscle Relaxants
Prototype Centrally Acting Skeletal Muscle Relaxants
Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins
Prototype Direct-Acting Skeletal Muscle Relaxants
Prototype Direct-Acting Skeletal Muscle Relaxants
Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins
Nursing Considerations for Centrally-Acting Skeletal Muscle Relaxants
Nursing Considerations for Centrally-Acting Skeletal Muscle Relaxants
• Assessment: History and Physical Exam
• Nursing Diagnosis
• Implementation
• Evaluation
Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins
Nursing Considerations for Direct-Acting Skeletal Muscle Relaxants
Nursing Considerations for Direct-Acting Skeletal Muscle Relaxants
• Assessment: History and Physical Exam
• Nursing Diagnosis
• Implementation
• Evaluation
Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins
Question Question
A patient experienced a musculoskeletal injury resulting in a great deal of pain in his lower back. How can the nurse augment the drugs to aid in pain relief?
A. Moist cold
B. NSAIDs
C. Passive exercise
D. Active exercise
Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins
AnswerAnswer
B. NSAIDs
Rationale: Provide additional measures to relieve discomfort—heat, rest for the muscle, NSAIDs, positioning— to augment the effects of the drug at relieving the musculoskeletal discomfort.
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