Ppt chapter 25

Muscle Relaxants
Chapter 25
Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins

Regulation of Movement and Control of
Muscles
• Spinal Reflexes
• Influences from Upper-level CNS Areas
– Basal ganglia
– Cerebellum
– Cerebral cortex

Types 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

Reflex Arc Showing Pathway of Impulses

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

Neuromuscular 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

Action 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

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

Question
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

Answer
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.

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

Centrally-Acting Skeletal Muscle Relaxants
(cont.)
• Contraindications
– Known allergy
– Rheumatic disorders
• Cautions
– Epilepsy
– Cardiac dysfunction
– Conditions marked by muscle weakness

Relaxants (cont.)
• Adverse Reactions
– Drowsiness
– Fatigue
– Weakness
– Confusion
– Headache
– Nausea

Relaxants (cont.)
• Adverse Reactions (cont.)
– Dry mouth
– Hypotension
• Drug-to-Drug Interactions
– CNS depressants

Direct-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

(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

(cont.)
• Contraindications (cont.)
– Hepatic disease
– Lactation
• Cautions
– Women
– All patients older than 35 years
– Cardiac disease

(cont.)
• Adverse Reactions
– Fatigue
– Weakness
– Confusion
– GI irritation
– Enuresis
• Drug-to-Drug Interactions
– Estrogen
– Neuromuscular junction blockers

Mechanisms of Muscle Relaxants

Use of Muscle Relaxants Across the
Lifespan

Prototype Centrally Acting Skeletal Muscle
Relaxants

Prototype Direct-Acting Skeletal Muscle
Relaxants

Nursing Considerations for Centrally-
Acting Skeletal Muscle Relaxants
• Assessment: History and Physical Exam
• Nursing Diagnosis
• Implementation
• Evaluation

Nursing Considerations for Direct-Acting
Skeletal Muscle Relaxants
• Assessment: History and Physical Exam
• Nursing Diagnosis
• Implementation
• Evaluation

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

Answer
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.

Ppt chapter 25

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