Pain Medications and Muscle Relaxers

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Pain Medications and Muscle Relaxers

• ESAT 4001
• Pharmacology in Athletic Training

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Pain and Analgesics

• Pain. Good, or bad?
• Pain usually prevents individual from continuing
  a harmful activity
• Masking pain. Good, or bad?
• Types of pain medications

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Non-Narcotic Analgesics

• Salicylates
• Aspirin
• Peripheral inhibition of prostaglandin synthesis
  analgesic effect
• Antipyretic effect as a result of inhibition of
  prostaglandin synthesis in the hypothalamus
• Possibly increases blood flow to skin causing
  sweating dissipation of heat

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Non-Narcotic Analgesics

• Ibuprofen
• Analgesic effect w/in 2-4 hr
• Acetaminophen
• Tylenol
• Weak prostaglandin inhibitor
• Useful in treatment of mild-moderate pain
• Can be supplemented by strong narcotic agent to
  increase potency for treating severe pain

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Narcotic Analgesics

• Codeine, morphine
• Exogenous opioids more powerful than endogenous
  opioids
• Opioid receptors
• Common side effects drowsiness, dizziness,
  blurred vision, nausea, and vomiting
• ADDICTION

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Anesthetics and Skeletal Muscle Relaxants
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Neuromuscular-Blocking Agents

• True skeletal muscle relaxants
• Decrease the response to the neurotransmitter Ach
  at the neuromuscular junction
• Also either depolarizes membrane (causes muscle
  twitch) or do not (no twitch)

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Depolarizing Drugs

• Succinylcholine only depolarizing NM-blocking
  agent used in US
• Effects are similar to ACh
• Longer effect than ACh

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How Succinylcholine Works

• Not metabolized effectively at synapse
• Membranes remain depolarized and unresponsive to
  stimulus
• Flaccid paralysis
• Continued exposure causes decreased
  depolarization membrane repolarizes
• Membrane cannot be depolarized by ACh as long as
  succinylcholine is present
• Desensitization of membrane by succinylcholine

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Non-depolarizing Drugs

• Tubocurarine
• Work in one of 2 ways
• Low dose attaches to nicotinic receptor,
  prevents ACh binding
• Works as long as dose is sufficient if more Ach
  is made available it will over power drug
• High dose blocks ion channels of the synapse
• Further weakens nerve transmission, makes ACh
  more inactive

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Cardiovascular Other Effects of
Neuromuscular-Blocking Agents
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Local Anesthetics

• Work only on area of administration
• Locals can block all nerves in area
• Sensory and motor functions blocked
• Surgical concern, will block both
• Continued athletic participation

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Action of Local Anesthetics

• Preferentially block small fibers due to shorter
  pathways
• Small-diameter fibers are first to fail to
  conduct
• Anesthesia of large, myelinated nerve requires
  that 3 successive nodes be blocked
• The thicker the nerve the farther apart the
  nodes greater resistance to blockade
• Myelinated tend to be blocked before unmyelinated
  of same diameter
• Exception to above nerve bundles

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Administration of Local Anesthetics

• Topical application
• Small-nerve injection
• Major nerve trunk injection
• Spinal cord infiltration
• Sympathetic fiber block

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Types of Local Anesthetics
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Central-Acting Muscle Relaxants

• Soma, flexeril, valium, robaxin, norgesic
• Actions
• Mechanism is not well understood overall effect
  is sedation
• All are general CNS depressant
• No evidence that they can selectively relax
  skeletal muscle
• Side effects
• Drowsiness, nausea, light-headedness, vertigo,
  ataxia, headache