I had a South Pole client years ago who had Raynaud's but did not tell us until he was in Antarctica
He eventually had to leave because his hands were too cold - we didn't actually let him get as far as frostnip - but in the later stages we did give him Nifedipine and that seemed to help some. If you used it regularly, or had other blood or health issues, you should consult your doctor about it. It's a real drug, it has effects.
In another category for circulation are things like Gingko Biloba and garlic supplements. GB does give some people hot flushes, but it's true efficacy is still being debated - for AMS included. Garlic can't hurt, but really may not be effective, and has to be taken in high, strong doses of quality product to have the intended effect. I tried GB on a couple of Antarctic expeditions but could not really tell a difference - but then I wasn't getting cold fingers to start with anyway.