13-Drugs for Pain Flashcards
Nociceptor pain
- pain produced by tissue injury
- receptors on nerve endings are activated & transit pain signals to the CNS
What are the 2 divisions of nociceptor pain? What are the pain descriptors?
- Somatic pain - sharp localized pain
2. Visceral pain - generalized dull, throbbing/aching pain
Neuropathic pain (what causes it & pain descriptors)
- pain caused from damage to neurons (due to a lesion/disease)
- direct nerve injury (damage from surgery, diabetic neuropathy, etc.)
- pain descriptors: burning, shooting, numbness
Acute vs Chronic pain
Acute: Intense pain occurring over a defined period of time (from injury to recovery/repair) - less than 6 months
Chronic: pain lasts longer than 6 months, interferes with daily activities, high incidence of depression. Not the same as end of life pain!
Explain what happens when tissue is damaged.
Tissue damage –> arachidonic acid is present –> converted to prostaglandins that blocks platelet aggregation and contributes to pain & inflammation.
Pain mediators such as histamine, bradykinins and PGs are released. Cytokines like pyrogens cause fever.
Substance P
- A neurotransmitter that is involved in the transmission of pain messages to the brain
- activates post-synaptic neurons –> pain signal travels along the thalamic tract to the brain
What 3 things inhibit the release of substance P?
- opioids (enkephalins)
- serotonin
- NE
These 3 substances send inhibitory signals down the descending tract (modulates the release of substance P).
Briefly describe steps in the transmission of acute pain.
- Tissue injury/trauma
- Pain transduction (release of mediators)
- Pain transmission: afferent neural transmission - to the CNS –> signal reaches spinal cord receptors (substantia gelatinosa)
- Pain perception & modulation: transmission to the brain (via the spino-thalamic tract)
*After pain transmission, there can be a reflex sympathetic response to the painful stimulus.
Pain Physiology
- Transduction: trauma stimulates nociceptors
- Transmission to peripheral nerves: pain impulse travels to spinal cord through A and C fibres
- Transmission in spinal tracts: Impulse continues along ascending tracts
- Perception: cortex recognizes pain stimulus
- Modulation: limbic system reacts to pain; modulating signals are sent along descending tracts.
T or F: The production and transmission of painful impulses can be modulated at specific stages of transduction/transmission.
False, it can be modulated at almost every stage.
Tylenol 3 contains?
- Acetaminophen: modulates substance P
- Codeine: an opioid
- Caffeine: enhances absorption
Vicodin
hydrocodone (opioid) + acetaminophen
What type of therapy refers to the use of varied techniques and multiple drug classes to achieve effective analgesia?
multi-modal therapy
Non-opioid analgesics includes:
Acetaminophen and NSAIDs
What are NSAIDs commonly administered for?
Relieving mild/moderate pain, inflammation & fever.
- insufficient to manage pain associated with extensive injuries or pain involving visceral structures (greater than 4 on the scale)
- Inhibits the inflammatory response to tissue injury
- inhibits COX –> PGs that induce pain + inflammation are not produced
Examples of non-selective COX inhibitors
ASA & ibuprofen (inhibits both COX 1 and 2)
Example of a selective COX inhibitor + which enzyme does it inhibit
Celecoxib - inhibits COX 2 so that PGs for pain + inflammation are not produced
NSAIDs act by inhibiting pain mediators at which level?
The nociceptor level
What should all analgesic regimens include? Why?
A non-opioid drug (acetaminophen/NSAID) - even in cases of severe pain!
Bc these drugs can reduce opioid requirements by ~ 30%
What do endogenous opioids do? Examples?
Modulate the transmission of pain to the brain and spinal cord. Includes beta endorphins & enkephalins.
What happens to the presynaptic & postsynaptic neurons when opioids bind to the receptors?
Presynaptic neurons: Closes Ca channels, inhibiting release of excitatory neurotransmitters (ach, substance P, glutamate)
Postsynaptic neurons: Opens K+ channels, causing membrane hyperpolarization, inhibiting neuronal activity
Which receptors do opioid drugs bind to to exert their analgesic effects? Where are these receptors located?
mu and kappa opioid receptors in the brain & spinal cord
When are opioid drugs used to treat pain?
When the pain is moderate-severe (especially pain in visceral structures) & cannot be treated by other analgesics.
How are opioid drugs used to treat acute pain?
Use the lowest dose for the shortest amount of time in combination with an NSAID (bc acute pain has an inflammatory component as well).
Clinical uses for opioid drugs (2)
Severe diarrhea & antitussive therapy (treat coughs)
Are opioid drugs commonly prescribed to treat chronic pain?
No, the use of opioids for chronic pain is controversial.
What does the canadian guideline for opioids suggest for chronic non-cancer pain?
- use non-opioid drugs & non-pharmacological therapy before giving opioids
- stabilize psychiatric disorders first
- don’t use opioids in clients with a substance abuse disorder
Exmple of an opioid antagonist (and what are the routes of administration)
naloxone (IV, IM, SC) - used to treat an opioid overdose
Symptoms of opioid withdrawal
- lacrimation
- rhinorrhea
- chills
- gooseflesh
- muscle aches
- diarrhea
- anxiety
- hostility
Adverse effects of opioids
- Constipation
- Nausea & Vomiting
- Pruritus
- Sedation
- Respiratory depression (naloxone)
- Delirium (opioid induced neurotoxicity)
Where are opioids metabolized and excreted? Which opioids produce active metabolites?
liver; urine
Active metabolites = morphine + codeine
Pain receptors in peripheral tissues can be blocked with local anaesthetic agents such as? How do these drugs work?
- lidocaine and bupivacaine
- they block afferent nerve transmission of pain (e.g. nerve block)
- can also be used at the level of the spinal cord (spinal or epidural techniques) to block afferent and efferent impulses including the sympathetic response
Endogenous pain suppression pathways release which 2 neurotransmitters?
GABA & serotonin
Benzodiazepines act on which receptor? What do they do?
GABA receptors; they intensify the effect of GABA at the receptor
*GABA is used to augment analgesia
T or F: SSRIs have a strong nociceptive effect.
False, they have little nociceptive effect!
Triptans bind to which receptors to treat what condition? How do triptans work?
5-HT1D receptors; migraine headaches
They have a vasoconstrictive effect on vessels in the skull and also inhibits the release of substance P to modulate pain.
Which steroids are used for pain management? What are they used to treat?
Dexamethasone, prednisone
Bone pain and nerve compression
Anticonvulsant drugs treat what kind of pain?
neuropathic pain
Pain is multi-dimensional, and incorporates?
- The physical stimulus
- The physical state of the patient
- The emotional state of the patient
- The patient’s past experience with pain
- The patient’s beliefs about the implications of being in pain
Pain
- Unpleasant sensory and emotional experience associated with actual or potential tissue damage
- patient reports the experience (requires communication)
Numeric rating score (NRS) is used for clients above the age of? What numbers correlate w/ mild, moderate & severe pain?
8
Mild: <4
Moderate: 4-6
Severe: 7-10
Alternate scales (other than the NRS) have to be used for which client populations?
- pre-verbal children (early developmental stage)
- developmentally delayed individuals (youth & adults)
- intubated patients
- patients w/ an altered LOC
What do behavioural observation tools measure? What doesn’t it measure?
- Measures the presence/absence of pain (e.g. facial expression, leg movement, activity, cry and eating, sleeping, etc..)
- Doesn’t measure intensity!!
The FACES scale is used for what age range? What does it measure?
4-18; intended to measure how children feel inside, not how their face looks
How should pain be assessed? (baselines?)
- baseline pain should be measured
- pain should be monitored to assess the therapeutic effect of analgesia
T or F: Pain is what the patient says it is; it is the health care providers responsibility to treat the pain.
TRUE
