Pain - Drug Choices For Analgesia

Front 1

Majority of drugs used for analgesia

Back 1

-opioids
-NSAIDs
-Local Anesthetics

Front 2

Analgesic drugs with no regional effects

Back 2

-NSAIDs
-Acetaminophen
-Antiepileptics

Front 3

Opioids
-use

Back 3

-most effective for most types of pain especially acute pain

Front 4

Opioids
-characterized by

Back 4

-analgesia without loss of proprioception or conciousness

Front 5

Opioids
-response depends on

Back 5

-opioid used (drug)
-species being treated
-age and gender of the patient
-condition or type of pain being treated (acute, chronic, somatic, visceral, neuropathic)
-individual animal (genetics)

Front 6

Opioids
-analgesic effects

Back 6

-directly inhibit/modulate ascending transmission of nociceptive information from the spinal cord dorsal horn
-activate pain control circuits that descend from the midbrain to the spinal cord dorsal horn

Front 7

Opioids
-non-analgesic effects

Back 7

-depression of respiratory center ----> decreased minute volume and increased arterial CO2
-increased GI tract tone with decreased peristalsis
-Vagally mediated decreases in HR
-Nausea and vomiting
-effected thermoregulation
-cough suppression
-increased ADH ---> dec. urine production
-histamine release (some opioids)
-Excitement and dysphoria

Front 8

Opioids
-vagally mediated decreases in heart rate are most evident with

Back 8

-potent mu agonists

Front 9

Opioids
-nausea and vomiting less likely in

Back 9

-partial agonists or mu antagonists

Front 10

Opioids
-effects on thermoregulation

Back 10

-hyperthermia in cats administered hydromorphone
-mild decreased temperature due to set point change

Front 11

Opioids
-drugs that can cause histamine release

Back 11

-morphine
-meperidine

Front 12

Opioids
-species susceptible to excitement and dysphoria

Back 12

-cats
-horses (Boxwalking)

Front 13

Questions to ask for choosing an opioid

Back 13

-What type of pain will be treated?
-How would you rate the intensity or degrees of pain that is occurring or will occur?
-How will the drug be given?
-What will the treatment interval be?
-Are there specific side-effects that you wish to avoid?
-What species is being treated

Front 14

Types of pain that may be treated with opioids

Back 14

-most frequently acute pain from surgery or trauma
-cancer pain may progress to where treatment with opioids is necessary
-acute exacerbation of chronic disease (IVDD, osteoarthritis)

Front 15

Specific opioid side effects that you may want to avoid

Back 15

-avoid vomiting with an esophageal foreign body
-hypethermia due to hydromorphone
-decreased GI motility in horses

Front 16

Opioids
-considerations for cats

Back 16

-high doses of mu agonists can cause dysphoria
-hyperthermia from hydromorphone

Front 17

Opioids
-considerations for horses

Back 17

-possible increased locomotor activity and GI motility

Front 18

Opioids to use when there are concerns of locomotor and GI side-effects in horses

Back 18

-Kappa agonists, mu antagonists (Butorphanol)

Front 19

Opioids
-Ruminant concerns

Back 19

-GI motility
-rumen atony

Front 20

Opioids
-avian concerns

Back 20

-kappa agonists may have better analgesia than mu agonists (unknown)

Front 21

Opioids
-main mu agonists

Back 21

-morphine
-hydromorphone
-methadone
-fentanyl

Front 22

Opioids
-main partial mu agonists

Back 22

-buprenorphine

Front 23

Opioids
-main kappa agonists, mu antagonists

Back 23

-butorphanol

Front 24

Opioids
-main antagonists

Back 24

-naloxone

Front 25

Methadone
-duration

Back 25

2-6 hrs
-longer duration clinically than morphine

Front 26

Methadone
-MOA

Back 26

-NMDA receptor antagonism

Front 27

Methadone
-pros

Back 27

-effective analgesic in horses with minimal excitatory effects

Front 28

Methadone
-cons

Back 28

-expensive

Front 29

Tramadol
-main MOA

Back 29

-inhibition of reuptake of norepinephrine and serotonin

Front 30

Most commonly used opioid in veterinary practice

Back 30

-morphine

Front 31

Morphine to use epidurally

Back 31

-must be preservative free

Front 32

Reason to use morphine epidurally

Back 32

-most water soluble opioid = longer duration of effect

Front 33

Epidural morphine
-pros

Back 33

-long duration of action (18-24 hrs)
-segmental analgesia (less sedation and behavioral effects)
-good analgesia with no effect on proprioception or motor function

Front 34

Epidural morphine
-cons

Back 34

-requires technical expertise
-increased cost
-need to shave the area over the lumbosacral spine (aesthetics, slow to grow back)
-potential side effects

Front 35

Epidural morphine
-potential side effects

Back 35

-urinary retention
-pruritis
-nausea and vomiting if the epidural is administered in awake animals
-delayed respiratory depression in people

Front 36

Major excitatory neurotransmitter in the CNS

Back 36

-Glutamate

Front 37

Glutamate receptors

Back 37

-AMPA
-Kainate
-NMDA******

Front 38

Glutamate receptor with the biggest effect on nociception

Back 38

-NMDA

Front 39

How do NMDA receptors differ from the other glutamate receptors?

Back 39

-high calcium permeability
-magnesium blockade at resting membrane potential
-may require glycine (co-agonist) for activation

Front 40

NMDA receptor
-structure

Back 40

-heterotetrameric assembly of different subunits

NMDA receptors don't all look alike
-mammals have 4 subunits of 2 receptors
-some cells have a 3rd subunit for glycine
-several isoforms of each subunit

Front 41

NMDA
-variance in subunit composition due to

Back 41

-location in the nervous system
-age of the animal

Front 42

NMDA
-reason for varied subunit composition

Back 42

-varied functions of a receptor

Front 43

NMDA at resting membrane potentials

Back 43

-inactive due to a blockade of extracellular magnesium even in the presence of glutamate

Front 44

How to activate an NMDA receptor

Back 44

--glutamate need to be released to bind to the receptor
-postsynaptic membrane needs to be depolarized to remove the magnesium blockade
-NMDA mediated calcium influx then activates a series of signaling molecules within postsynaptic cells

Front 45

NMDA receptor function on nociception

Back 45

-pivotal role in excitatory synaptic transmission and plasticity, including various brain processes such as memory ----> hallucination
-receptors are expressed in pain pathways from the periphery to the brain (critical role for triggering neuropathic pain)

Front 46

Synaptic pasticity
-define

Back 46

-ability of the synapse between two neurons to change in strength in response to either use or disuse

Front 47

NMDA
-where are all subunits expressed

Back 47

-dorsal horn

Front 48

Method of possibly causing analgesia with fewer side effects

Back 48

-designing specific NMDA antagonists to target a specific receptor subunit

Front 49

NMDA antagonist drugs
-nonspecific

Back 49

-amantidine
-ketamine
-phencyclidine
-nitrous oxide
-dextromethorphan
-memantine
-methadone
-tramadol

Front 50

NMDA antagonist drugs
-NR2B antagonist (specific)

Back 50

-ifenprodil

Front 51

Ketamine
-use

Back 51

-adjunct when treating chronic or neuropathic pain
-lower dose for analgesia than for anesthesia
-often used in surgery for procedures where substantial pain was present prior to the procedure
-adjunct analgesia for burn patients
-possibly effective for treating central sensitization

Front 52

Ketamine
-route of administration

Back 52

-CRI (must use)

Front 53

Ketamine
-surgeries where use may be indicated

Back 53

-total ear canal ablation
-limb amputation due to tremors
-severe trauma

Front 54

Burn patient
-analgesic treatment

Back 54

Fentanyl CRI
-remained tachycardic
-hunched up in cage
Ketamine
-seems more comfortable
-eats small amounts
Fluid and antibiotic therapy
Wound debridement (distal limb nerve blocks)
-off fentanyl
-buprenorphine
-continue ketamine
-discontinue ketamine

Front 55

NMDA anatagonist drugs
-drugs used to some success

Back 55

-amantidine
-dextromethorphan

*cause anxiety and restlessness