NM on one side and 25 on the other, round, slightly convex, white tablet, very powdery and bitter. I was prescribe nortriptyline 25 mg and was give a small bottle of these. They did not work at all. My doctor gave me a repeat prescription but this time the tablets were orangey yellow, no imprint except a line down one side. These tablets worked from the first dose. I called the pharmacy where I had filled my first script to double check I had been given correct medication and they, of course, reassured me I had but now I cannot find any images or descriptions of the first lot of meds.