Potions, by their very nature, can be used by anyone. "A given potion can only be used once, period, but it doesn’t face a surcharge for being usable by someone else," YS280, right above the bullet list on the right.
As for items, "The strength of an enchanted item may be reduced by one to make it usable by someone other than the caster, such as a magically armored coat that anyone can wear," YS179, second-to-last indent on the right column.
Unless designed otherwise, only the creator can use an enchanted item.
-EF