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Pain Medications and Muscle
Relaxers
ESAT 4001Pharmacology in Athletic
Training
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
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
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
Narcotic Analgesics
• Codeine, morphine• Exogenous opioids more powerful
than endogenous opioids• Opioid receptors• Common side effects – drowsiness,
dizziness, blurred vision, nausea, and vomiting
• ADDICTION
Anesthetics and Skeletal Muscle Relaxants
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)
Depolarizing Drugs
• Succinylcholine – only depolarizing NM-blocking agent used in US
• Effects are similar to ACh– Longer effect than ACh
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
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
Cardiovascular & Other Effects of Neuromuscular-Blocking Agents
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……
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
Administration of Local Anesthetics
• Topical application• Small-nerve injection• Major nerve trunk injection• Spinal cord infiltration• Sympathetic fiber block
Types of Local Anesthetics
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
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