If you are using B5 to treat oily skin, most people start out w/ 10 grams/day. Its a lot, but B5 is water soluble so whatever you don't need gets flushed out in urine. You only have to stay on 10g/day until your oil decreases to a level you're comfortable with. From there you can work down to about 2g/day.
It takes a while to work I think, you might not see any oil reduction for a few weeks and then it should start slowly going down.
When you take this much B5, you have to take a B-complex WITH the B5, too much of one B vitamin can cause deficieny in other B vitamins. I read you should also take zinc with it.
I never had any side effects from B5 but some people have had diarrhea the first few days.
xxxemmaxxx- you can order B5 online. do a search for B5 supplements.