Thanks for the interest and feedback, everyone. We have run a few sessions, and a couple of snorts after the character found out he had to give up his civilian identity and enter the espionage buisness were well timed and well played. The other charatcers have been handling the talking when he is in his worst shape, and I'm still ironing out the jitters of combat while high. The guy does really well at playing it, though, so I may just pull the rules mods and let him run with it, and just drop in a +/- 2 once in a while to keep it balanced.
As for dope, most of the mods should be negative, unless the character is trying to fit into a certain situation or calm his nerves. The Will save idea is a good one, but I wouldn't apply the mod just to Wisdom in general. Maybe a bonus to attention-oriented tasks like Craft or Research; task fixation is one thing associated with marijuana. Definately a bonus while using Gather Information at a Phish show. If your campaign has an arcane element, it might factor in to break down barriers and allow the charatcer to transcend to a different level of conciousness, man. I'd agree with the Init penalty, and a penalty to Ref saves as well.