THE VARIOUS DRUGS AND OTHER MISCELLANEOUS AGENTS USED FOR SMALL ANIMAL PAIN MANAGEMENT

1. MANAGEMENT OF PAIN IN
SMALL ANIMALS
PRESENTED BY ,
SWATHI KRISHNA
12 – BVP - 230

2. PAIN
• “UNPLEASANT SENSORY AND EMOTIONAL EXPERIENCE
ASSOCIATED WITH ACTUAL OR POTENTIAL TISSUE
DAMAGE”.

3. THE PAIN PATHWAY
Transduction
Transmission
Modulation
Perception

4. TRANSDUCTION
• Mechanical, chemical and thermal energy are converted into electrical
energy/impulses by specialized nerve endings called “nociceptors”.
• NOCICEPTORS
• Free nerve endings of primary afferent fibers.
• Have high stimulus thresholds for activation.

5. TRANSMISSION
Occurs along 2 different types of afferent nerve fibers:
A-DELTA FIBERS
• Large diameter
• Myelinated
• Rapid impulse conduction (6-30 m/sec)
• Stimulates immediate reaction

6. C FIBERS
• Small diameter
• Unmyelinated
• Slow conduction
• (0.5 – 2 m/sec)
• Reinforces the immediate response that is signaled by a-delta
fibers.
Spinothalamic tract
• Most important tract in transmission of nociceptive information.
Spinoreticular tract
Spinohypothalamic tract

7. MODULATION
• SIGNAL PROCESSING
• Spinal cord
• Dorsal horn
• Endogenous systems
Tissue trauma
Signal enters dorsal horn
Reflex activity
exits ventral
horn
To higher
levels of
CNS
CROSS SECTION OF THE SPINAL CORD

8. PERCEPTION
• RECEIVING AND INTERPRETATION
• Successful transduction, transmission, &
modulation of a painful stimulus.
Modulation
Perception

9. TYPES OF PAIN
 PERIPHERAL PAIN
Visceral
• abdominal or thoracic organs
• poorly localized
• referred
Somatic
 superficial
• skin
 deep
• tendons, joints, muscle, periosteum

10. PHYSIOLOGICAL PAIN
• It is a protective mechanism and causes avoidance.
• Little to no tissue injury.
• Pain stops once the stimulus is removed.
PATHOLOGICAL PAIN
• It results from tissue injury and causes inflammation ,
nerve damage etc.
• Persists after the stimulus is received.

11. NEUROPATHIC PAIN
• Damage to peripheral nerves or spinal cord.
• Often difficult to treat appropriately.

12. ACUTE PAIN
• Arises from soft tissue trauma or inflammation.
• Plays a biologically adaptive role by facilitating tissue repair.
CHRONIC PAIN
• Pain that persists beyond the expected time frame for a given
disease, process or injury.
• May be associated with ongoing inflammation.
• May be autonomous with no temporal relation to the inciting
cause.

13. ADAPTIVE PAIN
• Normal response.
• Protects from further injury.
• Inflammation is a large component.
MALADAPTIVE PAIN
• Abnormal response.
• Stimulus is gone but pain persists.

14. FACTORS AFFECTING PAIN
• STRESS
• ANXIETY
• WIND-UP
• CENTRAL SENSITIZATION

15. COMMON BEHAVIORAL RESPONSES TO PAIN
• Dogs arepack animals, theyshareemotions with pack members to receive
support.
 Whine, whimper
 Arched or abnormal posture
 Guarding of injured tissue
 Restlessness
 Behavior change
 Increased heart rate and blood pressure
 Hypersalivation
 Appetite reduction
 Dilated pupils
 Altered voiding behavior

16. Cats aremore solitary animals, they aregenerally more stoic thandogs; showing pain
highlights a cats vulnerability.
 Over grooming
 Hiding
 Squinting
 Guarding injured tissue
 Desperate attempts to flee
 Reduced grooming
 Appetite reduction
 Pupil dilation
 Salivation
 Restlessness
 Increased heart rate and blood pressure

17. STRESS RESPONSE MARKERS/PAIN ASSESSMENT
Heart rate
Respiratory rate
Blood pressure
Posture
Attitude
Food and water intake
Patterns of defecation, urination
Change in activity levels
Natural behaviors – inquisitive,
grooming
Provoked behavior
Aggression
Gait-/Posture
Vocalization
Appearance of stereotypical
behaviors

18. ACTIONS OF ANALGESICS ON PAIN
PROCESSES
TRANSDUCTION:
• Can be blocked by local anesthetics by injection either at the site of
injury/incision or intravenously.
• Can be decreased by use of NSAIDs which decrease the production of
prostaglandins at the site of injury.
TRANSMISSION:
• Can be prevented by local anesthetics by injection along peripheral nerves,
at nerve plexus, or in the epidural or subarachnoid spaces.
MODULATION:
• Can be augmented by injection of local anesthetics or alpha2-adrenergic
agonists; gabapentin may also effect modulation.
PERCEPTION:
• Altered by use of general anesthetics or systemic injection of opioids and/or
alpha2-agonists.

19. GENERAL APPROACHES TO PAIN
MANAGEMENT
o PRE-EMPTIVE ANALGESIA: Giving analgesics prior to the noxious stimulus
(surgery)
• By blocking or inhibiting the nociceptive process before it begins,
hypersensitivity is prevented.
• May decrease the amount of anesthesia and post-operative analgesia
needed.
o MULTIMODAL OR “BALANCED” ANALGESIA: Using a combination of analgesics
which will impact more than one portion of the nociceptive process.
• for example: buprenorphine and meloxicam pre-surgically, lidocaine block
used prior to incision, and bupivicaine splash prior to closing incision

20. ANALGESICS
 DIVIDED INTO FIVE MAIN CLASSES BASED ON MODE OF ACTION
• OPIOIDS
• NON-STEROIDAL ANTI-INFLAMMATORY DRUGS
• LOCAL ANESTHETICS
• ALPHA2-ADRENOCEPTOR AGONISTS
• MISCELLANEOUS DRUGS

21. OPIOID ANALGESICS

22. OPIOID CLASSIFICATION
AGONISTS
• Stimulate receptor activity
• MU agonists
• most common group of opioid agonists used
• include morphine, meperidine, oxymorphone,
hydromorphone, fentanyl, carfentanil
AGONISTS-ANTAGONISTS
• Stimulate activity at some receptors and antagonize others
• Butorphanol – kappa agonist, mu antagonist

23. • PARTIAL AGONISTS
• Bind to receptor but only produce a partial effect
• Buprenorphine – partial mu agonist, kappa antagonist
• ANTAGONISTS
• Primary activity is mu receptor antagonism
• Naloxone
• Naltrexone
• Nalmefene
• Diprenorphine

24. OPIOID RECEPTOR PHARMACOLOGY
• CLASSIFICATION: 4 types μ, κ, ε, σ
MU
• supraspinal, spinal, peripheral and analgesia , respiratory depression ,
euphoria/sedation , physical dependence , bradycardia.
KAPPA
• spinal analgesia , sedation , respiratory depression.
SIGMA
• dysphoria/hallucinations , hypertonia , respiratory stimulation , tachycardia.

25. OPIOID ADMINISTRATION
• SYSTEMIC: IV, SQ, IM, CRI
• INTRA-ARTICULAR INJECTION
• LOCAL INJECTION
• EPIDURAL INJECTION
• TRANSDERMAL FENTANYL PATCH

26. GOOD
 GREAT ANALGESIA
 VARIABLE MUSCLE RELAXATION
 SEDATION
BAD
 RESPIRATORY DEPRESSION
 GI EFFECTS
• vomiting
• defecation followed by
constipation
 EXCITEMENT
 DEPRESSION OF THE COUGH
CENTER
OPIOID EFFECTS

27. OPIOID SPECIES SPECIFIC EFFECTS
Excitement in cats (dose related).
Panting in dogs – resets thermostat.

28. MISCELLANEOUS ANALGESICS

29. TRAMADOL
• Synthetic opioid agonist which also inhibits serotonin and norepiniphrine
re-uptake in the spinal cord.
• The main metabolite has moderate opioid activity.
KETAMINE
• NMDA antagonist.
• Used as a cri during surgery at sub-anesthetic doses, it reduces mac and
can help prevent hypersensitivity
• More effective treating somatic pain than visceral pain
• Can be administered via epidural injection
GABAPENTIN
• Analogue of naturally occurring neurotransmitter GABA.
• Believed to increase production of GABA.
• part of endogenous inhibition of nociception
• Used to treat nerve pain.

30. NON-STEROIDAL ANTI-
INFLAMMATORY DRUGS ( NSAIDS )

31. • NSAIDS are weak organic acids with anti-inflammatory, analgesic,
and antipyretic properties.
• Inhibit prostaglandin production by inhibiting cox enzymes.
• Are either non-selective (inhibits both cox iso-enzymes) or
selective for cox-2.
• Non-selective NSAIDS have more serious side effects (gastric
ulceration and renal toxicity).
• Decreased renal blood flow during anesthesia makes kidneys more
susceptible to toxic effects.
• Cyclooxygenase inhibition decreased thromboxane decreases
platelet adhesion/clumpingdecreases clot formation and
thromboemboli.

32. TYPES OF NSAIDS

33. PHENYLBUTAZONE
COX1 AND 2 INHIBITOR
VERY POTENT
COMMONLY USED IN HORSES
NOT RECOMMENDED IN DOGS
• GI SIDE EFFECTS COMMON
• NEVER IN CATS!

34. ASPIRIN
• COX1 AND 2 INHIBITOR
• VERY SHORT HALF-LIFE IN HORSES
• COMMONLY USED IN DOGS
• BUFFERED ONLY
• WITH FOOD
• USE WITH CAUTION IN CATS
• CAN’T METABOLIZE WELL
• HALF-LIFE 38 HOURS
• DOSED EVERY 48-72 HOURS

35. KETOPROFEN
• KETOFEN® (COX1 AND COX2)
• LICENSED IN HORSES
• APPROVED FOR USE IN DOGS AND CATS IN CANADA, EUROPE
• GOOD ANALGESIA, POTENT ANTIPYRETIC
• INJECTABLE
• LIMIT USE
• BLOOD CLOTTING

36. FLUNIXIN MEGLUMINE
• BANAMINE® (COX1 AND COX2)
• INJECTABLE
• HORSES
• COLIC
• GOOD ANALGESIA
• DOGS
• GI SIDE EFFECTS COMMON, SEVERE

37. CARPROFEN
• RIMADYL ®
• COX-2 INHIBITOR: “SPARES” “GOOD” PROSTAGLANDINS
• FEWER SIDE EFFECTS
• DOGS ONLY
• BLACK LABS…
• 0.06% OF ALL DOGS DEVELOP HEPATIC PROBLEMS (RARE)
• BID DOSING

38. ETODOLAC
• ETOGESIC ®
• COX 1 AND 2 INHIBITION
• ONCE DAILY ADMINISTRATION
• DOGS ONLY

39. DERRAMAX
• USE IN DOGS
• COX 2 SPECIFIC
• SID DOSING

40. “METACAM” =MELOXICAM
• COX-2 SPECIFIC
• USE IN DOGS AND CATS
• LIQUID
• WELL TOLERATED

41. ALPHA2-ADRENERGIC AGONISTS

42. Stimulation of the alpha2 – adrenoceptors result in sedation,
muscle relaxation, and analgesia.
Two alpha-2 agonists (xylazine, medetomidine) and 2 antagonists
(yohimbine, atipamezole) are approved for use in small animals in
canada.
Another alpha-2 agonist, romifidine, is approved for use in
horses, but not in dogs and cats.

43. LOCAL ANESTHETICS

44. • LOCAL INFILTRATION OF SURGICAL SITE
• INTRAVENOUS REGIONAL ANESTHESIA
• INTRA-ARTICULAR INJECTION
• NERVE BLOCKS
• EPIDURAL
• TOPICAL ON SKIN/ EYE/ LARYNX
The “-caine” family: Lidocaine, bupivicaine, mepivicaine,
proparicaine, tetracaine, etc.

45. EPIDURALS
• Administered alone or in combination with other
analgesics.
• If combined, smaller doses can be used, decreasing
risks of adverse effects.
• Can cause motor deficits at higher doses.

46. MISCELLANEOUS AGENTS

47. CAPSAICIN
• This medication is used to treat minor aches and pains
of the muscles/joints (e.g., arthritis, backache, sprains).
capsaicin works by decreasing a certain natural
substance in the body (substance p) that helps pass pain
signals to the brain.

48. ST. JOHNSWORT
• Arthritic pain
• Stimulates neural inhibitory pathways analgesia

49. CHONDROPROTECTIVE AGENTS
• NUTRACEUTICALS
• chondroitin sulfate
• glucosamine
• hyaluronic acid
• building blocks for cartilage and synovial fluid
• Examples: (oral) synovi, glycoflex (injectable) adequan can be mixed with many
other ingredients (MSM, creatine) to enhance effects.

50. THANK YOU……….