13-Drugs for Pain

Question 1

Nociceptor pain

Answer 1

• pain produced by tissue injury

- receptors on nerve endings are activated & transit pain signals to the CNS

Question 2

What are the 2 divisions of nociceptor pain? What are the pain descriptors?

Answer 2

1. Somatic pain - sharp localized pain

2. Visceral pain - generalized dull, throbbing/aching pain

Question 3

Neuropathic pain (what causes it & pain descriptors)

Answer 3

• 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

Question 4

Acute vs Chronic pain

Answer 4

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!

Question 5

Explain what happens when tissue is damaged.

Answer 5

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.

Question 6

Substance P

Answer 6

• 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

Question 7

What 3 things inhibit the release of substance P?

Answer 7

• opioids (enkephalins)
• serotonin
• NE

These 3 substances send inhibitory signals down the descending tract (modulates the release of substance P).

Question 8

Briefly describe steps in the transmission of acute pain.

Answer 8

1. Tissue injury/trauma
2. Pain transduction (release of mediators)
3. Pain transmission: afferent neural transmission - to the CNS –> signal reaches spinal cord receptors (substantia gelatinosa)
4. 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.

Question 9

Pain Physiology

Answer 9

1. Transduction: trauma stimulates nociceptors
2. Transmission to peripheral nerves: pain impulse travels to spinal cord through A and C fibres
3. Transmission in spinal tracts: Impulse continues along ascending tracts
4. Perception: cortex recognizes pain stimulus
5. Modulation: limbic system reacts to pain; modulating signals are sent along descending tracts.

Question 10

T or F: The production and transmission of painful impulses can be modulated at specific stages of transduction/transmission.

Answer 10

False, it can be modulated at almost every stage.

Question 11

Tylenol 3 contains?

Answer 11

1. Acetaminophen: modulates substance P
2. Codeine: an opioid
3. Caffeine: enhances absorption

Question 12

Vicodin

Answer 12

hydrocodone (opioid) + acetaminophen

Question 13

What type of therapy refers to the use of varied techniques and multiple drug classes to achieve effective analgesia?

Answer 13

multi-modal therapy

Question 14

Non-opioid analgesics includes:

Answer 14

Acetaminophen and NSAIDs

Question 15

What are NSAIDs commonly administered for?

Answer 15

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

Question 16

Examples of non-selective COX inhibitors

Answer 16

ASA & ibuprofen (inhibits both COX 1 and 2)

Question 17

Example of a selective COX inhibitor + which enzyme does it inhibit

Answer 17

Celecoxib - inhibits COX 2 so that PGs for pain + inflammation are not produced

Question 18

NSAIDs act by inhibiting pain mediators at which level?

Answer 18

The nociceptor level

Question 19

What should all analgesic regimens include? Why?

Answer 19

A non-opioid drug (acetaminophen/NSAID) - even in cases of severe pain!
Bc these drugs can reduce opioid requirements by ~ 30%

Question 20

What do endogenous opioids do? Examples?

Answer 20

Modulate the transmission of pain to the brain and spinal cord. Includes beta endorphins & enkephalins.

Question 21

What happens to the presynaptic & postsynaptic neurons when opioids bind to the receptors?

Answer 21

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

Question 22

Which receptors do opioid drugs bind to to exert their analgesic effects? Where are these receptors located?

Answer 22

mu and kappa opioid receptors in the brain & spinal cord

Question 23

When are opioid drugs used to treat pain?

Answer 23

When the pain is moderate-severe (especially pain in visceral structures) & cannot be treated by other analgesics.

Question 24

How are opioid drugs used to treat acute pain?

Answer 24

Use the lowest dose for the shortest amount of time in combination with an NSAID (bc acute pain has an inflammatory component as well).

Question 25

Clinical uses for opioid drugs (2)

Answer 25

Severe diarrhea & antitussive therapy (treat coughs)

Question 26

Are opioid drugs commonly prescribed to treat chronic pain?

Answer 26

No, the use of opioids for chronic pain is controversial.

Question 27

What does the canadian guideline for opioids suggest for chronic non-cancer pain?

Answer 27

- 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

Question 28

Exmple of an opioid antagonist (and what are the routes of administration)

Answer 28

naloxone (IV, IM, SC) - used to treat an opioid overdose

Question 29

Symptoms of opioid withdrawal

Answer 29

- lacrimation - rhinorrhea - chills - gooseflesh - muscle aches - diarrhea - anxiety - hostility

Question 30

Adverse effects of opioids

Answer 30

- Constipation - Nausea & Vomiting - Pruritus - Sedation - Respiratory depression (naloxone) - Delirium (opioid induced neurotoxicity)

Question 31

Where are opioids metabolized and excreted? Which opioids produce active metabolites?

Answer 31

liver; urine | Active metabolites = morphine + codeine

Question 32

Pain receptors in peripheral tissues can be blocked with local anaesthetic agents such as? How do these drugs work?

Answer 32

- 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

Question 33

Endogenous pain suppression pathways release which 2 neurotransmitters?

Answer 33

GABA & serotonin

Question 34

Benzodiazepines act on which receptor? What do they do?

Answer 34

GABA receptors; they intensify the effect of GABA at the receptor *GABA is used to augment analgesia

Question 35

T or F: SSRIs have a strong nociceptive effect.

Answer 35

False, they have little nociceptive effect!

Question 36

Triptans bind to which receptors to treat what condition? How do triptans work?

Answer 36

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.

Question 37

Which steroids are used for pain management? What are they used to treat?

Answer 37

Dexamethasone, prednisone | Bone pain and nerve compression

Question 38

Anticonvulsant drugs treat what kind of pain?

Answer 38

neuropathic pain

Question 39

Pain is multi-dimensional, and incorporates?

Answer 39

- 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

Question 40

Pain

Answer 40

- Unpleasant sensory and emotional experience associated with actual or potential tissue damage - patient reports the experience (requires communication)

Question 41

Numeric rating score (NRS) is used for clients above the age of? What numbers correlate w/ mild, moderate & severe pain?

Answer 41

8 Mild: <4 Moderate: 4-6 Severe: 7-10

Question 42

Alternate scales (other than the NRS) have to be used for which client populations?

Answer 42

- pre-verbal children (early developmental stage) - developmentally delayed individuals (youth & adults) - intubated patients - patients w/ an altered LOC

Question 43

What do behavioural observation tools measure? What doesn't it measure?

Answer 43

- Measures the presence/absence of pain (e.g. facial expression, leg movement, activity, cry and eating, sleeping, etc..) - Doesn't measure intensity!!

Question 44

The FACES scale is used for what age range? What does it measure?

Answer 44

4-18; intended to measure how children feel inside, not how their face looks

Question 45

How should pain be assessed? (baselines?)

Answer 45

- baseline pain should be measured | - pain should be monitored to assess the therapeutic effect of analgesia

Question 46

T or F: Pain is what the patient says it is; it is the health care providers responsibility to treat the pain.

Answer 46

TRUE