Analgesics Concept Lab MASTERY GUIDE 2025: 72 Expert-Curated Q&A with Step-by-Step Rationales, Dosing Protocols, and Clinical Safety Applications

Somatosensory system

sensory network that monitors the surface of the body and its movements

the nervous system consists of two parts

central and peripheral

CNS (central nervous system)

brain and spinal cord

PNS (peripheral nervous system)

cranial nerves ( all the nerves outside of the brain) and spinal nerves

what is the nervous system responsible for ?

the receipt of external stiumuli and for many of the bodys response responses to stimuli (pain) that include:

**glandular secretion

**musculoskeletal control

what is the fundamental unit of the nervous system

a nerve cell

the soma

cell body of a neuron- transmits information

the dendrites

Branchlike parts of a neuron that are specialized to receive information.

what does the somatosensory system include?

afferent and efferent neurons

afferent neurons

"SENSORY"

Nerve cells that carry impulses towards the central nervous system

efferent neurons

motor neurons

*carry information from the central nervous system to the muscles ----helps control involuntary and voluntary movement and reflexes

peripheral nervous system includes what type of somatic receptors?

skin, muscles, and joints

there are nerve endings in the PNS that serve as the receptors for the following:

***crude (non-localized) touch

***temperature

**nociceptive pain

when the somatic receptors receive sensory information what happens to the information?

transmitted to the spinal cord, and from the spinal cord to the brain

Neurotransmission

the process of transferring information from one neuron to another at a synapse

Synapse

the junction between the axon tip of the sending neuron and the dendrite or cell body of the receiving neuron

presynaptic neuron

neuron that sends the impulse

postsynaptic neuron

neuron that receives the signal

synaptic cleft

gap between adjacent neurons

spinal cord

*carries sensory information to the brains, and motor information from the brain to the rest of the body

how many pairs of nerves does the spinal cord have?

31 pairs

each pair has ascending and descending pathways that sends information

ascending pathways in spinal cord

the nerves in the front send sensory information UP the spinal cord to the brain

descending pathways of the spinal cord

the nerves in the back send motor signals from the brain down the spinal cord to the rest of the body

incoming sensory information and outgoing information are processed by

the thalamus

what happens when sensory signals are transmitted up the spinal cord to the brain?

the thalamus receives the information and transmits it to the sensory cortex

the sensory cortex

the part of the brain that determines how hard and where sensory information is perceived

what is the sensory cortex part of the brain

determnines how and where sensory information is perceived

sensory signals are sent from

the PNS -> up to the spinal cord -> to the brain

the pathophysiology of pain

transduction, transmission, perception, modulation

chronic pain

persistent or recurring pain that lasts for extended period of time (longer than 3 months)

acute pain

short-term, self-limiting, often predictable trajectory; stops after injury heals

**usually caused by tissue injury, and resolved by treatment to the underlying damage

nociceptive pain

acute pain; a pain sensation that results abruptly

neuropathic pain

pain from damage to neurons of either the peripheral or central nervous system

Pain characteristics

1. dull aching, poorly localized, but max over pubic symphysis

2. aggravated by standing on 1 leg. radiates into groin and lower abdomen

3. maybe either unilateral or bilateral

pqrst

provocative/palliative, quality, region/radiation, severity, timing

OLD CARTS

Onset

Location

Duration

Characteristics

Aggravating and Alleviating Factors

Related Symptoms

Treatment

Severity

FLACC

face, legs, activity, cry, consolability

pain severity

important to determine both the kind of analgesic medication to be administered and the dose of that medication

Wong-Baker FACES scale

a pain assessment tool that asks patients (often children) to select one of several faces indicating expressions that convey a range from no pain through the worst pain

two types of nociceptive pain

somatic pain and visceral pain

somatic pain

receptors are found in the skin, subdermal tissue surrounding bones and joints

visceral pain

receptors are found in internal organs and the connective tissues surrounding those organs

*visceral pain resulting from injury is likely to be localized and sharp, white visceral pain caused by blockage often feels more diffuse and cramping

nociceptive pain vs neuropathic pain

nociceptive pain- results form activation of pain receptors

neuropathic: results from damage to the nervous system itself (burning, , tingling, shooting pain-neuropathy)

*caused by the body's own pain reporting system**

treatment for neuropathic pain

adjuvant analgesics

anticonvulsants (gabapentin, carbamezepine used to treat both nerve pain and seizures)

Pregabalin -nerve pain medication

nociceptors

found in skin, joints, and viscera - are sensory neurons responsible for receiving and relaying pain

nociceptor nerve fibers two major types

delta fibers ( lightly myelinated)

C-fibers

myelinated axons

axons covered with myelin sheaths- which plasma membrane wrapped around the axon

* this membrane ENHANCES the axon's conductive quality-info travels faster along myelinated axons rather than un-myelinated axons

lightly myelinated A delta fibers

communicate initial sensation of pain

unmyelinated axons

C fibers that communicate the severity of the pain

descending pathway

pain is mediated at several points along the descending pathway -- as a result of neuro-chemnical interactions which occur naturally within the body

endogenous opioids

endorphins and endogenous monoamines like serotonin ---change both the perception f and the response to pain

inflammation

occurs when the immune system reacts to injury, helps to restore normal function to damaged tissue

four signifiers of ACUTE inflammation

redness

heat

swelling

pain

what does inflammation do

increases prostaglandin production-which in turn furthers these signs of inflammation

fever

body's temperature is set by the hypothalamus ---> when responding to and infection .. elevated levels of prostaglandin E2 causes the hypothalamus to set the body's temperature at a higher point- this causes vaso constriction which decreases heat loss--->>> process continues until the blood bathing the hypothalamus reaches new elevate set point

substances which cause fevers are called

pyrogens

pyrogens can be

exogenous or endogenous

analgesics pharmacotherapy

now that we have gone over the pathophysiology of pain--- this lab will focus on the pharmocotherapies that are used to treat pain at different levels of severity

acetaminophen pharmocotherapy

***known as paracetamol and abbreviated APAP -- analgesic drug used to treat mild to moderate pain and a FEVER reducer.

-not an anti-inflammatory

*reduces fever by acting directly upon the hypthalamus to reset the bodys core temperature

mechanism of action : acetaminophen (fever)

fever occurs when the hypothalamus sets the body's temperature higher than usual ---usually in response to a pathogen--- acetaminophen acts upon the hypothalamus to inhibit this activity

mechanism of action of acetaminophen for pain

there are several theories its analgesic mechanism of action -one os the more prominent ones is that aceteminophen's analgesic effect is due to the inhibition of prostaglandin synthesis

effect: acetaminophen

OTC

**dont receive higher than maximal amount of acetaminophen daily - processed primarily through the liver (as well as kidney's and intestine)

*hepatotoxicity is a possible ASE*

acetaminophen summary

Overview:

*works against mild to moderate pain and reduces fever

*analgesic mechanism of action for acetaminophen is unknown

care considerations:

>can contribute to acute liver failure

>an ingrediant in mnany common OTC drugs

>prevent overdose -the total amount of acetaminophen from all sources should not exceed the daily maximum

***pediatric acetaminophen dosing should be weight based**

also weight based for anyone under 50 kg

mechanism of ibuprofen

*nonselective NSAID

-bind an arginine molecule at position 120 in both COX-1 and COX-2 enzymes, blocking arachidonic acid from entering the channel

Celecoxib (Celebrex)

NSAID

COX-2 inhibitor like celecoxib are associated with a decresaed risk of adverse GI effects

but they can increase cardiovascular risk---- it was this increased risk that led to rofecoxib and valdecoxib being taken off the market--- leaving celecoxib the only selective COX-2 inhibitors can still have a negative effect on the GI tract

aspirin

NSAID and non-NSAID

it is a non-steriodal drug used to treat pain, its effects and mechanism of action change depending upon the size of the dose adminsitered

aspirin at a low dose

functions as a preferential COX-1 inhibitor -low doses of aspirin act primarily on COX-1 to reduce platelet aggregration and decrease the likelihood of blood clots -asprin inhibits platelet aggregation for the life cycle of the platelet

apsirin at a moderate rate

functions as a non-selective cox-1 and cox-2 inhibitor and reduces pain and fever

aspirin at a higher dose

anti-inflammatory

*comes with an increased risk of adverse effects

effects of aspirin

*rapid absorption of aspirin from the stomach increases the risk of gastric toxicity

*aspirin has anticoagulant effects:blocks platelet aggregation and decrease platelet adhesives

*aspirins anticoagulant effects increase bleeding time

*aspirin and other NSAIDS reduce renal vasodilation

*cause immunological reaction leads to acute intersitial nephritis

*decrease renal vasodilation and the risk of interstiral nephritis increase the likelihood of acute kidney injury

*aspirin increases the risk for Reye's syndrome in children, espically those with influenza or varicella

NSAID summary

*anti-inflammatory

*mechanism of action involves inhibiting COX enzymes

*there are non-elective, COX-2 selective, and cox-1 preferntial NSAIDs

Opioid summary

*powerful class of anaglesics used to treat several chronic and acute pain

*opioid mechanism of actioni is innately tied to the central neverous system

*regulation guiding opiod used can cary by region

*opioids are a mojor contributor to deaths due to drug overdose

*overuse of opioids is a worldwide public health crisis