New information regarding subcutaneous ketamine

At the recent Association of Veterinary Anaesthetists conference in Liverpool there was an abstract presented examining subcutaneous ketamine in dogs. The study was entitled ‘A randomized, double-blinded, placebo-controlled parallel-group pilot study evaluating the effect of low-dose subcutaneous ketamine as an adjunctive analgesic in dogs with osteoarthritis’ and was conducted by Nielsen and colleagues from the University of Copenhagen.

In their introduction they point out that SC ketamine is a component of multimodal analgesia, albeit with unproven efficacy. The information we feature in our original article on this topic is anecdotal and based on experience. The protocol that we have advocated is 0.5 mg/kg starting on a monthly basis and titrating according to individual response.

Read our original post here

In the trial reported, 16 dogs were included – all documented to have clinical osteoarthritis. Eight dogs were randomised to the ketamine group and 8 to the placebo group. All dogs were treated with an existing pain management plan and this plan had to have been initiated 4 weeks prior to the start of the trial. Clients and assessors were blinded to treatment groups. Dogs in the ketamine group received 0.5 mg/kg SC on day 0. This was a single injection with no repeats.

Dogs were assessed at day 0, 7, 14 and 28. Outcome measures were;

• Canine Brief Pain Inventory

• Canine Osteoarthritis Staging Tool

• Pain – assigned by clinician

• Passive range of motion

• At day 28 clients were asked if they could tell which group their dog was in.

Results

Pain scores	Decreased from day 0-14 (p = 0.02) in ketamine group
PROM scores	Decreased from day 0-7 (p = 0.03) and from 0-14 (p = 0.03) in ketamine group
PROM scores	Decreased significantly day 0-7. This was the only significant change in the placebo group.
CBPI pain interference scores	Decreased more in the ketamine group than placebo but this was not significant days 0-7
Client assessment	12/16 owners correctly identified which group their dog was in

Author conclusions

The authors concluded that ‘low-dose ketamine additional to ongoing pain treatment in dogs with osteoarthritis points towards a significant effect on pain on manipulation and PROM scores from day 0 to day 14. Further investigation is warranted’.

Our view is that this is a really promising piece of work. The data collected can be used for a sample size calculation to assess the number of dogs required in each group to document a statistically significant difference.

Points to note

• We should be cautious about statistical significance from this current work as groups were small and there is no mention of a sample size calculation.

• CBPI scores decreased most in the first 7 days. This could suggest that monthly dosing is not optimal and would be a key factor to assess in any future study.

• With the clients able to assess which group their dog was in, it would be good to include caregiver reported outcome measures in any future study.

• In canine analgesia studies a placebo effect is documented in approximately 30% - hence the need for a suitable sample size.

Future work will help ascertain whether the value of SC ketamine is as a rescue treatment or an ongoing analgesic therapy

References

Nielsen MB et al (2026) A randomized, double-blinded, placebo-controlled parallel-group pilot study evaluating the effect of low-dose subcutaneous ketamine as an adjunctive analgesic in dogs with osteoarthritis. Proceedings of the Association of Vetereinary Anaesthetists meeting Liverpool.