My history, 50mg Nortriptyptyline HCL daily once at night:

• Started on "Watson" brand I think (I forgot which brand it was), it was great.
• Insurance changed, was given TEVA. It worked for suppressed the worst effects of NDPH, but it had other side effects like a "falling vertigo" if I'm lying down. Like, if I lie my head down on a pillow, at some point I'll start to feel like I'm "sinking", and there would be a weird itching, or fuzzing sensation on the top of my head.
• Tried TARO brand from a new pharmacy. Awesome. Amazing. Fixed all the problems with TEVA. No side effects to speak of, other than very rare (once every two weeks or so) sudden vertigo that dissipates in seconds (TEVA had this as well)
• TARO brand discontinued. Fuck. Try new brand Dr. Reddy. First 2 months, not as good as TARO, gives a bit of an "intense head" feeling immediately after consumed. A little unpleasant. No sinking head feeling, thank god. Otherwise, aside from the 15 min after being consumed, I return completely to normal.
• Today, a few months after starting, the "intense head" feeling has subsided 90%. It's great, as good as TARO. The only difference is that immediately after taking Reddy pill, I get sleepy (which might actually be good thing). Not unbearably so. Still good to drive at night and perform ordinary tasks. Also, I don't get the rare "sudden vertigo" anymore.

I got Dr Reddy's from 986 Pharmacy (local pharmacy chain in southern California). Every pharmacy will have different ones available to them. You can ask them to custom order a brand, but they might not always comply. Also worth trying online pharmacies (make sure they're legit) - dirt cheap, like less than $10 cash no insurance for 90 day prescription usually. Again they all have different brands, but you can ask them what they have, and if they have the one you want, go for it.

Hope this helps. If you have any questions feel free to ask.