I've been reading up on street drugs after reading some of the threads about mundane humans, and was wondering about how it would effect a shapeshifter.

How would the stun damage from many of them be handled? Would they just heal it and move on? And it's hard to think they would take any permanent damage from abusing drugs, because well, they can't take any permanent damage....

I realize their are no rules for shifters in SR4, but still, any ideas on how this would be handled? Would they basically get to use and abuse as much as they want because they can heal it up?

I would rule that they would "heal" the drug effects out of their system immediately. Basically, all drugs would have a duration of only 1 turn, or however long it takes to regenerate. Then maybe they take crash effects for another turn, then those are all better, too.
I suppose they could get effects by keeping a constant stream of combat drugs pumping into them, but that would be expensive, and probably be highly addictive. If not physically, mentally.

Addiction is a serious thing.
Often times, though, it's not the physical craving so much as the mental craving.
If a shifter were able to easily shrug off the physical consequences of a drug, I'd be inclined to rule that the mental addiction gets stronger, causing them to take more and more doses, and push the edge of what the body can take before going down.

Sounds like a pretty sweet NPC villain, though. Not the main boss, but the boss's whoop-ass underling. The drugged up shapeshifter would be like Dark Maul, to Darth Sidious.

Exactly! That's what makes it so absurd it could only be done by some exec with more money than sense. Sure, the thing will burn out and be a miserable failure, who cares? It'll annoy the PCs greatly during it's very short lifespan.
edit: An autoinjector carries, what, 10 doses? That's 30 seconds of fun. More than enough time for a one-fight NPC.
edit edit: And just to explain the Darth Maul comment, the parallel I was going for is that it's freaky looking, scary in a fight, but only has a few minutes of screen time, which is entirely composed of combat, after which it dies and is forgotten. Oh, and no characterization.

Slappatches are described as giving continaul safe amounts of a chemical. Might it be possible to have some made up with kamikaze or someo ther drug and have it last a few combat turns?

Stansfield seemed to be using some sort of fast hitting, quickly fading drug. Getting up for the fight/interogation. He had characterization. Characterization that was bizzarely cartoonish, but still there with an odd depth to it.

Just saying you could go either way with it. Backdrop sidekick fodder or main scheming villian.

EDIT: That's a good idea Squinky, slapping a patch should be able to get him up for a bit. For some reason that reminds me of the Simpsons episode where Crusty tries quiting smoking and plasters his entire body with nioderm patches.

EDIT2: Some awakened drugs might also avoid being quickly metabolised by the shapeshifter.

Also note that neural and genetic damage arn't regenerated at all, so a drug which acts one way might be flushed in seconds, while a drug with a different activity might behave normally.

-Frank