One of the questions from the ketamine webinar was 'if I use a ketamine infusion in a dog already on memantine, do I stop the memantine'.
My approach here is to stop the memantine while the dog is in hospital. The ketamine should be doing the NMDA action we require. To be honest, we have experience with this - but no studies. (We don't have any studies on memantine for pain - only experience.)
There is more info on amantadine and memantine here
You can watch the ketamine webinar here