For lower maintenance doses, NAD+ is frequently given as a subcutaneous injection, meaning a small volume is injected just under the skin (for example, in the abdomen, thigh, or back of the arm)
Not to be indelicate, but does glutathione - cough, cough - influence your bowel movements and make you poop
It is difficult to say that one medication universally causes more side effects than the other because the studies involved different people and used different methods
Oxidative Medicine and Cellular Longevity, 2012, Article 324832
An 8-week randomized double-blind trial compared GHK-Cu in a nano-lipid carrier against Matrixyl 3000 and found a 55.8% reduction in wrinkle volume versus control serum, along with a 32.8% reduction in wrinkle depth
The short answer is YES