Well... if you drink a potion with a 3rd level spell (preferably fireball on yourself), you'll have to make a check against a DC 10+3 (spell level)+ damage. Looks weird and doesn't really make sense, but that looks like it.SRD: Drinking a potion or using an oil on an item of gear is a standard action. The potion or oil takes effect immediately. Using a potion or oil provokes attacks of opportunity. A successful attack (including grappling attacks) against the character forces a Concentration check (as for casting a spell). If the character fails this check, she cannot drink the potion. An enemy may direct an attack of opportunity against the potion or oil container rather than against the character. A successful attack of this sort can destroy the container.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.