To be honest with you, he is probably going to be okay. However, this is harm reduction, and if you really are worried about his fate, then take him somewhere.
Personally, if I was your friend, even if I was acting that way, I wouldn't want you to take me anywhere. I would want you to give me a chance to come down a little bit first. I've never seen anyone react that way to IV heroin or methamphetamine. Was this his first time using?
I say he will probably be fine because I've personally had and witnessed many anomalies in individual's reactions to drugs, and the result was always eventually them being fine.
Keep us updated.