Common side effects (nausea, constipation) typically decrease over time
Anticancer Res 21 (4B), 28952900 (2001) Chopra, A., Saluja, M., Tillu, G., Sarmukkaddam, S., Venugopalan, A., Narsimulu, G., Handa, R., Sumantran, V., Raut, A., Bichile, L., Joshi, K., Patwardhan, B.: Ayurvedic medicine offers a good alternative to glucosamine and celecoxib in the treatment of symptomatic knee osteoarthritis: a randomized, double-blind, controlled equivalence drug trial
Because NAD is a supplement, its not regulated by the FDA and claims around efficacy dont have to be proven (which is required of prescription medications)
E., Helmick, C