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