5. Management chronic pain continued Flashcards
Approach to treatment chronic pain:
Needs to be holistic for best outcome ABCDE = holistic management A = Analgesia B = Bodyweight C = Control of complications, common sense and comfort D = Disease modification E = Exercise
When approaching treating chronic pain. What 2 categoreis can analgesia be subdivided into?
- Pharmaceuticals (analgesic drugs)
2. Analgesic interventions, including complementary adn physical therapies
Give examples of analgesic interventions
acupuncture, physiotherapy, hydrotherapy
Photobiomodulation (laser therapy)
Transcutaneous electrical nerve stimulation (TENS)
Palliative radiotherapy
Analgesic drugs e.g
NSAIDs Piprants (grapiprant) Paracetamol Tramadol NMDA antagonists Gabapentin and pregabalin Tricyclic anti-depressants e.g. amitriptyline Others: bisphosphonates, lidocaine patches, capsaicin and cannabinoids
Waht to remember when treating chronic pain as a vet…
consult a chronic pain specialist for advice or even refer the case if you are struggling to manage a case with chronic pain and/or suffering associated with it.!
NSAIDS MoA
• Anti-inflammatory effect through the inhibition of cyclooxygenase (COX)
NSAIDS - why inhibit cyclooxygenase?
• Cyclooxygenase = enzymes that produce prostaglandins, promote inflammation, pain adn fever
NSAIDS main drug for what and side effects?
Mainstay of treatment for nociceptive/inflammatory pain – particularly OA
Multiple side effects so long term use must hvae serum biochem and urinalysis every 6 months
Piprants e.g. Grapiprant
Non-steroidal, non-COX inhibiting anti-inflammatory drug
REcently licensed in dogs usefu; for those that don’t tolerate NSAIDS
Why is Grapiprant better to use than NSAID if dog sensitive to them?
Grapiprant is a prostaglandin E2 EP4 receptor antagonist. The EP4 receptor is involved in the development of pain and inflammation associated with OA.
NSAIDs which will inhibit prostaglandin production at all EP receptors including the ‘constitutive’ prostaglandins that are involved in maintaining GI mucosal integrity and renal perfusion.
Paracetamol
Licensed for oral use in dogs (combined with codeine) for up to 5 days
Can be used ‘off license’ for chronic pain management in dogs – usually well tolerated
Often classified as NSAID but poor anti-inflammatory properties
Analgesic mechanisms not fully understood
May be used with/without NSAIDs – consider in patients with renal disease
Minimal veterinary literature but anecdotal reports of analgesic efficacy
Toxic for cats – NEVER USE
Tramadol
Licensed in dogs - acute and chronic mild soft tissue and musculoskeletal pain
Inhibits serotonin and noradrenaline reuptake
Atypical opioid – weak mu receptor agonist
M1 metabolite - greater analgesic efficacy (greater affinity for mu receptor) than parent drug
Efficacy in dogs very variable – some are not able to produce M1 metabolite
Can be effective in cats – slower clearance of M1 metabolite
May mask GI pain when used concurrently with NSAIDs
Side effects: salivation, vomiting, dysphoria, sedation and seizures
Bitter taste/poor palatability
NMDA antagonists
e.g.
Ketamine
Amantadine (not licensed in veterinary species)
Memantine (not licensed in veterinary species)
Slow onset (3-4 weeks)
Common side effects: transient GI signs
May cause agitation/restlessness
May lower seizure threshold
Gabapentin and pregabalin (BEEBEE!)
Not licensed in veterinary species
Predominantly used as anti-convulsants
Calcium channel antagonists – analgesic mechanisms not fully understood
Neuropathic pain
May be useful in animals that cannot tolerate long term NSAIDs
Side effects: sedation, vomiting and ataxia (sometimes polyphagia in cats)
May cause seizures if stopped abruptly
Renally excreted (care with renal disease)
Pregabalin – oral absorption more rapid and predictable than gabapentin with longer dosing interval
Amitriptyline
Not licensed in veterinary species
Tricyclic anti-depressant
Neuropathic pain
Central opioid receptor activity and serotonin and noradrenaline reuptake inhibitor
- do not use with other serotonin or NA reuptake inhibitors e.g. tramadol
May cause cardiac arrhythmias (ventricular tachycardia and fibrillation) in dogs
Bitter taste ptyalism in cats
Physioltherapy aim
To rehabilitate animals and return them to function following surgery, disease or injury
Muscle strengthening and useful for myofascial pain
Hydrotherapy
helps..
Water helps animals to regain strength, fitness and balance – provides buoyancy and resistance
Joints can be worked and extended without concussive pressure
What is Photobiomodulation?
Hwo does it help with chronic pain
LAser therapy
gaining popularity in veterinary medicine.
thought to reduce pain and inflammation by reducing pro-inflammatory mediators and cytokines at the treatment site, as well as reducing depolarisation of C fibres (slow pain fibre) and increasing release of endorphins and serotonin.
What is Transcutaneous electrical nerve stimulation (TENS)
Relies on sensory nerve depolarisation to suppress pain at level of spinal cord – similar to acupuncture
Used widely in humans but may not be well tolerated in animals
Muscle strengthening - rehabilitation/ physiotherapy
Contraindications – cardiac pacemaker, seizures, abdominal area during pregnancy, site of malignant neoplasia
Pallative radiotherapy
well recognised for palliative treatment of pain associated with osteosarcoma in dogs
It has also been shown to be effective for canine OA reduced inflammation and joint swelling
Multiple side effects e.g. long-term tissue damage (including nerve damage) and scarring
Cannot currently be recommended as a treatment for OA
BODY WEIGHT
How is it associated with OA
Obesity is common in animals with OA
Obesity = chronic, low level inflammatory state
- adipokines can exacerbate OA
Moderate weight loss can reduce pain scores and improve quality of life in animals with OA
Weight loss is arguably the single most important thing that owners can implement to help with chronic pain management in overweight animals. Unfortunately, obesity is very common in animals with OA (particularly with reduction in exercise tolerance and muscle atrophy over time without concurrent dietary restriction).
Obesity in itself is a chronic low-level inflammatory state and adipokines can exacerbate the pain and inflammation caused by OA
Control of complications, common sense and comfort
SEvaral factors…
Owner compliance improves if aware of side effects and complications of treatment
Involvement of the owner in the management process e.g. teaching appropriate massage techniques that can be performed at home improved compliance and owner satisfaction
Common sense and comfort = environmental modifications
Examples of environmental modifications for dogs
Ramps for vehicular access Non-slip rugs/mats on laminate flooring Restriction of upstairs access Raised food and water bowls Carts to allow rest periods during walks Supportive bedding
Examples of environmental modifications for cats
Use of steps/ramps to allow access to heights/favourite areas
Provision of new hiding places
Raised food and water bowls and ensure easy access to these resources (ideally different rooms)
Modification of cat flaps/outdoor access
Introduction of new games to adapt play behaviour
What is “disease modification” about?
All about obtaining a correct diagnosis
In those cases that cannot diagnose:
OFten injury has healed and left with OA
Polysulphated GAGs, pentosan polysulphate and hyaluronan injections
Potential chondro-protective and chondro-regenerative effects
Also can use nutraceuticals
Exercise adn chronic pain
rest?
Only Strict rest only for acute conditions (e.g. post surgical or OA flare up) or those where pain is exacerbated by exercise
Poorly fitting harnesses or use of collar and lead can contribute to an animal’s pain by applying additional pressure in painful areas.
If telling woner to restrict exercise, how to make more interesting?
emntal stimulation,
scent
Chronic pain in horses
More difficult to identify as prey species = hide. Acute pain much easier to identify.
Chronic= more subtle e.g. mild lameness, reduced appetite and weight loss, reduced interaction with owner, changes in facial expression
Drugs to use for chronic pain in horses
NSAIDs = main liek sA
Ketamine CRI (sub-anaesthetic doses) – limited evidence
Paracetamol – laminitis and compartment syndrome
Gabapentin – laminitis and neuropathic pain
Tramadol – limited evidence
Soluble epoxide hydrolase inhibitors e.g. t-TUCB – laminitis
Continuous peripheral nerve blockade (local anaesthetics)
Food producing animals and chronic pain
Limited licensed pharmaceutical options: NSAIDs Paracetamol (licensed in pigs) Ketamine – licensed for sedation and GA Cannot use opioids Consider withdrawal periods
