If you have salt on hand, I'd use it. The sooner you start treating it, the better.
I've never dealt with ich before, but a lot of people here don't necessarily like the medication anyways, since it's mostly just chemicals you're adding to the water.
It's not a bad idea to look around the forum quick to see if medication works better for some people.. you can always start the salt and then switch to the medication. I always hear great things about salt treating most diseases very well, so it should suffice.