Edition 6 - chronic pain in cats

Chronic pain in cats. Recent advances in clinical assessment.

The aim of the research roundup is to provide vet professionals with an easy-to-read digest on three items of research in pain management which focus on one common subject area. These research roundups provide a single point of reference for the reader.

Subject

Chronic pain in cats

Link to the publication here

Detailed review of the paper

It’s great to see such comprehensive guidelines available. As guidelines, they are a fairly chunky document, so we’ve brought you some highlights here!

The review starts with a reminder of the mechanism of action of NSAIDs, providing the reader with a concise update on key points with mention of the risk of peripheral sensitisation evolving to central sensitisation with either prolonged or poorly controlled pain. The authors stick with the traditional view that inhibition of COX-1 results in adverse effects whereas the inhibition of COX-2 results in therapeutic benefit – and then add that COX-1 can be involved in inflammation and COX-2 can play a homeostatic role. The COX-1/COX-2 picture remains unclear to us and these authors state that differential COX inhibition with different NSAIDs remains theoretical.

Metabolic pathways in cats are considered, as it is known that this is the reason for paracetamol (acetaminophen) being toxic to cats due to their inability to metabolise via glucuronidation. Of the NSAIDs currently licensed in cats, meloxicam is metabolised by oxidation pathways and the metabolism of robenacoxib is unclear. Knowledge regarding safety and efficacy of other NSAIDs is limited.

The review covers other anti-inflammatory drugs with this summary;

·      Grapiprant – limited safety and efficacy data – use not recommended

·      Metamizole – limited data – not recommended

·      Corticosteroids – not considered primarily analgesic

·      Paracetamol – contra-indicated

The rationale for using NSAIDs in chronic pain relates to the role that prostaglandins play in inciting the nociceptors in the periphery and triggering changes in central processing. The main example of chronic pain in cats is degenerative joint disease (DJD) and this review includes other causes of peripheral inflammation such as urinary tract disease (FLUTD), dental disease, uveitis and cancer.

Details of studies can be found within the guidelines and a summary is provided here;

·      FLUTD

Studies have focussed on overall impact of NSAIDs on management of the disease rather than the pain aspect per se. NSAIDs are recommended in this patient population, with consideration given to hydration status during the course of administration.

·      Dental & oral disease

NSAIDs are considered to play a role in both long term management of dental disease and also acute pain management with tooth extraction.

·      Neoplasia

The expression of COX by certain neoplasms provides a rationale for the use of NSAIDs in cancer pain management. Studies using NSAIDs in this way are reviewed in the publication.

Assessment of chronic pain

The use of owner reported measures in DJD is well-recognised and these focus on recognition of behaviours associated with pain. The authors provide a useful table which summarise the options available to vet professionals. Following this is a table which summarises the behavioural signs associated with different types of pain and clinical findings which may be detected. Further on in the review, the section ‘monitoring the clinical response to NSAIDs’ comes back to outcome measures to ensure that we can document a response to NSAIDs.

Pain trials

Box 3 in the text approaches the topic of pain trials. You can read more about pain trial in our Pain Update here.

Screening prior to NSAID therapy & follow up

This is a really useful part of this publication and makes recommendations for history, physical exam and laboratory testing prior to long term NSAID treatment. In a separate section the authors make recommendations for follow up testing in cats receiving chronic NSAID therapy.

Choice of NSAID and dose

·      Licensed options are meloxicam or robenacoxib.

·      Choosing between these involves consideration of palatability, ease of administration, availability and formulation.

·      In agreement with the authors, we recommend following licensed dosing indication. Although the review panel do mention lowest effective dose, there is no robust data to support this.  

Practicalities & considerations

NSAID switching is considered and reasons for this are given. The topic of a washout period is discussed, with the authors recommending a 7-day washout if the switch is due to adverse effects.

Anaesthesia – in particular anaesthetic management of cats receiving long term NSAIDs is discussed.

Co-morbidities

With the evidence demonstrating that 69% of cats with DJD also have chronic kidney disease (CKD) the authors devote attention to this topic by reviewing the current literature – revealing that the evidence base is weak in our ability to support or refute the long-term use of NSAIDs in cats. The detail provided is useful to support clinicians in our discussions with owners. Box 8 provides a useful summary. We should also remember that other options now exists in the form of the anti-nerve growth factor products for treatment of DJD without concern for renal compromise.

Adverse drugs effects

Prevalence of ADEs in cats is unknown for NSAIDs. These adverse effects are often a result of prostaglandin inhibition, including gastrointestinal, renal and hepatic effects. Under-reporting of ADE is thought to contribute to a lack of knowledge in this area.

Interaction with other drugs

Table 4 presents useful information and a quick reference when considering prescription of NSAIDs alongside other drugs.

Alternatives to NSAIDs

Further detail on these alternatives can be found in our webinars on chronic pain management in cats.

Frunevetmab – anti-NGFs are considered first line treatments for DJD in cats

Gabapentin – one small study was able to document a positive effect, although sedation is a concern. Further work is required looking at greater numbers of subjects. We don’t recommend gabapentin as a first line option when licensed options exist.

Pregabalin – studies to date have identified an anxiolytic effect and further studies are required to examine analgesia.

Tramadol – two small studies document a positive benefit, although use is hampered by the bitterness of this drug.

Amantadine – again, a small study which documented improved caregiver-identified impaired mobility and quality of life in cats with OA, although activity was decreased in the treatment group.

The review finishes by looking at environmental modification, supporting the knowledge that chronic pain management is more than just drugs.

Key points to aid reflection

There has been an increase in the literature in this area, which is well summarised here – how does this change your view?

Which pain scores will you incorporate?

What is your first line analgesic option for cats with OA?

Do you have a second line analgesic in mind?

How can we communicate the value of environmental modification to cat owners?

Everyone should read this

The resources provided on this webpage really help us with diagnosis and recognition of pain in cats, particularly that related to OA.

Recommended review article

Long-term pain in cats: how much do we know about this important welfare issue

Article link here