Arthro-IonX would be safe to give your cat because it contains micronutrients that are easy to assimilate and is homeopathic in nature to help cleanse the cells, reduce inflammation, and stimulate healing. Inflammation makes arthritis pain worse. Arthritis medications would put additional burden on the kidneys so you would not want to do this. Taking the natural route might be a better alternative in your case.
In addition to the Arthro-IonX I would suggest a canned kidney - formulated diet, digestive enzymes, and probiotics to improve digestion and reduce the workload on the kidneys. Highly digestible protein is important because cats need protein but you don't want low quality protein that can't be used and has to be disposed of by the kidneys. The enzymes and probiotics help to reduce the workload, too. Another product that is helpful is made by Standard Process; it is a supplement for cats called Feline Renal Support that is food for the kidneys. Arthro-IonX should give you the quickest response as the other things take more time to see results. Please keep us informed of your progress and if we can answer any more questions.