Following jdales line of thinking, add a bonus for number of ranks in body dev too. Additionally, if the addicted soul receives treatment, or can treat himself, another bonus could apply. Using the Static Mnv Tables, successful use of a secondary skill should provide a +20 to the roll.
You can also use Sd in place of Co as the primary stat. An argument for Pr can be made too.
So, base roll is Co, Sd and Pr mod + ranks in body dev + (20 with successful secondary skill such as hern lore, horticulture, second aid, etc).
Or pay a local Animist 24bp per herb to have them cleansed of addition factor, or whatever price your game world demands (I charge 4bp per spell lvl). There is also a spell to help cure addiction if all else fails (Heal Addiction spells on Healer base list).