Chapter 3 - Pain Flashcards
What are considered the most painful conditions in cattle?
- C-section
- Claw (pezuña) amputation
Meaning of sensation + perception…
Pain
Meaning of proprioception?
Sensation of lower level neurologic and biochemical components
3 functions of nociception
- Warning of damage
- Predicting tissue damage
- Warning of specific dangers
Who receives the sensory information related to pain?
Nociceptors in the tissues
Which mechanisms modulate nociceptor stimuli?
Spinal and Supra-spinal
Which are the two main responses after nociceptor stimuli?
Acute: Withdrawal stimuli
More complex: Aggression or escape
Meaning of allodynia?
Pain resulting for an innocuous stimuli
How can you assess nociception in animals?
Nociceptive threshold tests
Mention the most common nociceptive threshold tests? (4)
- Frey filaments: reaction to pressure
- Hargreaves: thermoreceptors
- Pressure allometry: painsensitivity in a sole ulcer lesion
- CO2 laser thermal stimulator: 45-55 C x 20 sec
Pharmacologic interventions to treat pain (5)?
- Local anaesthetics
- NSAIDs
- Opioids
- alpha 2 - agonist
- NMDA agonist receptors
Pharmacologic interventions to treat pain (5)?
- Local anaesthetics
- NSAIDs
- Opioids
- alpha 2 - agonist
- NMDA agonist receptors º
Only analgesic approved for use in food animal?
Flunixin
When does the use of extra label drug use (ELDU) is allowed?
- Supervision of a vet
- FDA approved in animals and humans
- Animals health is threatened
- Food destination - prohibited
- If volatile drug residue - prohibited
Describe nociceptive pathway: T-T-M-P-P
Transduction
Transmission
Modulation
Projection
Perception
MOA: Local anaesthetics
Enter and block Na+ channels of nerve cells. Prevent generation and propagation of nerve impulses
Local anaesthetics have better effect on unmylinated of myelinated fibers?
Unmyelinated
Why does local anaesthetics don’t work well in acidic environments?
Because they are weak bases and need alkaline environments
What can you use to potentiate effect of local anesthetics?
Magnesium sulfate
Sodium bicarbonate
+- Ethanol
How does magnesium sulfate helps local anesthetics?
Acts as a NMDA antagonist
Inhibit calcium influx into the cell
How does bicarb helps local anesthesics?
Reduces pain infiltration, acts faster but it might last less
How does ethanol improves local anesthetics ?
It demyelinates fibers, but you may need other injection for complete desensitisation
Prostaglandins interact with ______, _____, ______, and _____, in inflammation
Substance P
Histamine
Calcitonin gene related peptide
Bradykinin
In the spinal cord, ______ is responsible for increased excitability of the dorsal root ganglia.
PGE2
Oral bioability of oral flunixin meglumine
60%
Topical bioability of flunixin in cattle
45%
Rare but reported adverse effects of phenylbutazone administration. Reason why in humans is not used
Aplastic anemia
Leukopenias
Agranulocytosis
Thrombocytopenia
Half-life of Ketoprofen
0.45 h - 27 minutes
Examples of salicylic acid derivates
Aspirin and Sodium salicylate
In cattle why the half life of salicylic acid derivates is longer than iv?
Because it stays in the rumen, acts as a reservoir. It has slow absorption but limited distribution
Can we use Carprofen?
No, there is no approved formulations in USA
Half life of Meloxicam
27.5 h - good for long lasting analgesia
Where does opioids have main effect?
Spinal and supra spinal cord
Which receptors does opioids bind?
Mu
Kappa
Sigma
MOA: Opioids
Decreases propagation of nociceptive signals by activating receptor linked potassium channels and inhibiting calcium channels
Which opioid receptor is associated with more adverse effects?
The ones with more Mu receptors attachment
Which opioid receptors has less adverse effects?
Kappa
MOA of alpha-2-adrenergic agonist
Inhibits positive feedback of norepinephrine release from presynaptic nerve endings by reducing Ca conductance
MOA of NMDA receptor antagonist (analgesia)
Bind to Mu and Kappa opioid receptors
MOA of gabapentin (GABA analog)
Bind to a subunit of voltage gated calcium channel to decrease excitatory transmission
