You may use ARTHRO-IONX, PROMAXOL, or DERMA-IONX along with other medications or supplements so it is OK to use with any of those. It is homeopathic in nature and so it will not negatively interact with other physical substances. Please let me know which product you are interested in, if it is not one of those.
To dose the homeopathic I would split the dose and give 1/2 dose with breakfast and 1/2 dose with supper. After improvement you can give a whole dose on one of the meals. In addition I would give PROBIOTICS and OMEGA 3,6,9 which helps to improve the body and so I use them if there is pain, allergies, or skin issues. I hope you will not need to use Apoquel for more than a few months. You might want to Google side effects when there is long term use.
I would recommend having a veterinary chiropractor check your dog. It often improves movement.
Please let us know how you do.,