Page 54 - WSAVA2018
P. 54

 25-28 September, 2018 | Singapore
drugs (NSAIDs) should also be considered when there is a suspicion of pain. The truest assessment of the presence of pain is response to analgesics resulting in return to normal behaviours12.
There are no pathognomonic or unique clinical signs that characterize pain or that are present in every painful individual. Cats cannot directly communicate their discomfort to us. Several pain scoring systems exist, however they are either for assessing acute pain or have not been validated. The Feline Musculoskeletal Pain Index14 is the exception and may be a starting point for non-musculoskeletal pain. Fear (especially in the clinic) may look like pain and some patients may be experiencing both. With patients and in a quiet, calm environment, it can be easier to identify signs of pain. Look for at least three indicative signs in the history, behavioural changes and examination3. (See Figure 2).
Figure 2: Triangulation for identifying chronic pain. Adapted from Bergadano3
The experience of pain is different for every individual, both in severity, duration and impact. An analgesic regimen, using single or multiple agents, needs to be tailored to the individual’s needs through empathic and repeated assessment.
Wherever possible, pre-emptive analgesia should
be used to prevent stimulation of nociceptors and transduction of pain. Central sensitization can be prevented at the level of the N-methyl-D-aspartate (NMDA) receptors in the dorsal horn of the spinal cord. Ketamine is used, not only for its properties as a dissociative analgesic agent, but also specifically to block these receptors, thereby acting as an analgesic and as an anti-hyperalgesic agent.
When pre-existing inflammation, inadequate peri- operative analgesia with resultant neuropathic pain
exist, or if the cause of pain cannot be treated, then
an effective analgesic protocol must be developed in order to provide the patient with the best quality of life possible. Providing multimodal, balanced analgesia impacts multiple sites of the pain pathway while reducing the risk of negative effects from any one class of drug. This may be achieved through the concurrent use of an opioid with an NSAID and possibly amantadine (NMDA receptor antagonist) for maladaptive pain. Analgesic choices and doses for cats are listed in Table 1.
Analgesia for chronic musculoskeletal disease
The cat with joint pain is often an older patient who may have concurrent problems (e.g., renal disease) including some that may affect drug metabolism15. Like painful patients of any age, they may be in a physiologic state that affects drug disposition, the most common ones being dehydration, inadequate tissue oxygenation, electrolyte or acid-base imbalances and malnutrition. The most common concern regarding NSAID side effects is the possible consequence of using this class of drug in a dehydrated patient resulting in effects on gastric mucosal health or on renal function16. Dehydration may be subclinical and difficult to assess in the very young and
in the older cat due to the unreliability of skin elasticity in these age groups. (Stool consistency [i.e., pellets rather than formed logs] can be helpful in evaluating hydration.)
Opioids are safe for pain relief in any age group and are excellent when used at the same time as other agents, especially NSAIDs. They are not, however, a first drug
of choice for cats with arthritic pain as they are not
very effective for DJD. This is not to suggest that they shouldn’t be used for “break-through” pain or for comfort during diagnostic testing. If they produce adverse side- effects (e.g., euphoria, constipation and inappetence) in an individual patient they may be reserved for palliative hospice care.
Pharmacokinetic data is lacking for safe, long-term use of many NSAIDs in cats. Carprofen half-life varies from nine to over 40 hours in cats17,18. As most NSAIDs have long half-lives in cats when compared to other species, one precaution to avoid toxicity is to reduce the frequency of administration. Interestingly, despite having a short half- life of under 2 hours in blood, robenacoxib (Onsior®) its effect persists for 24 h in clinical studies.
Metacam® 0.5 mg/ml oral suspension has been granted a licence in the EU for the alleviation of inflammation and pain in chronic musculoskeletal disorders in cats. The registered dose is 0.1 mg/kg on the first day followed
by 0.05 mg/kg orally once daily. This is the first NSAID licensed for long-term use in cats.
Numerous efficacy studies have been performed regarding both of these NSAIDs. In one, clients felt
that cats treated for one month with meloxicam were more willing to jump achieving progressively higher heights during the study. Evaluation of the cats by the veterinarian at the end of the month showed a significant reduction of gait stiffness 19. Three studies have evaluated long-term safety of this agent in older cats; one concluded that this agent is safe, efficacious and palatable for musculoskeletal pain at 0.01-0.03 mg/kg PO q24h for a mean treatment duration of 5.8 months; no deleterious effect on renal function was detected in cats studied. Gastrointestinal upset in 4% of cats was the only adverse effect noted20. The second and third, reviewed

   52   53   54   55   56