Nice post. There are some inaccuracies that I'd like to point out though. Number one is that there are different meanings based on the region in which "spliff" is used. Some people mean it to be a joint, others mean it to be half weed half tobacco, and others use the term to mean a rolled cigarette with crack-cocaine sprinkled in with the tobacco. Weed does impair heroin users, even during withdrawal. It's not the same, and by no means a substitute, but if a heroin addict has no tolerance for weed, it will likely get them sufficiently stoned. Your explanation of someone experiencing withdrawal is true for some. But no two people experience the mental instability in the same way. I've known people be able to kick heroin cold-turkey. It sucked for them, but they didn't go crazy. In the same vein, I've seen people totally lose it, commitment to psychiatric hospital included. The range is nearly unlimited. Saying that all addicts experience it one way is a tad misleading. A long term addict, or short term addict, will not die directly from withdrawal. Opiate withdrawal is NOT lethal. Which is not to say that someone wouldn't die from complications of underlying medical conditions. But an otherwise healthy addict (I know, silly term, but they exist) will not die directly from the overdose. Opiate withdrawal is not as medically severe as alcohol or benzodiazepine withdrawal. As for first time users, there is truth in what you've said. But it's not experienced the same way. Shooting heroin for the first time will not cause someone's stomach to evacuate immediately like meth or cocaine. The puking comes later if it comes at all. Same goes for memory loss, it's not experienced by allfirst-timee users, I wouldn't even be able to safely say half.
I meant the weed spliffs. I do not think that a heroin addict on withdrawal symptoms would just get by with a spliff. I highly doubt it. They are waaay passed the state were they get even remotely high with a single spliff. Maybe a whole bag could be some sort of comfort, but only as such. He needs heroin. Only this specific substance will make the pain and paranoia to go away. I've met many people (some very close friends too) that were hooked on heroin. Some indeed cut it cold-turkey. The extreme minority that were the ones that had used for the shortest of time amongst the rest. They were also the ones that had more support from their friends and families. But even with these people, it was not easy. They went mental (in their own personal way) and had bouts. I think that this part is inescapable. I've never met a heroin junkie, never, that didn't lose him/herself at that point and even after. Actually it's so dramatic that the death I meant is self committed. But of course I'm not speaking about all the junkies of the world. I'm speaking about the ones that I've experienced. Many different characters living in many different conditions, to place them all in one cauldron.
http://americanaddictioncenters.org/withdrawal-timelines-treatments/heroin/ "Withdrawal from heroin isn’t generally considered life-threatening on its own; however, some of the medical and psychological symptoms may have complications that may be life-threatening."
yep - basically you have regular powdered coke (aka snow, blow, charlie, classic, etc) which is generally taken by snorting lines off a flat surface with a rolled up bank note or straw , and then you have crack which is made by 'cooking' regular coke into rocks ( I can't remember how, and i'm certainly not going to look it up on a work computer), which are then heated and smoked in a crack pipe Both are addictive, but crack is much more so (2 pipes is enough to make a regular person an addict) , the OPs characters could therefore split a line of coke if they needed an upper (although as i said its not fantastic for good judgement) but they'd be certifiable to use crack.
In my previous job, we used Benzodiazepines. Wanna zone someone out? maybe these could help. Others have listed some variants above but here's a link... https://www.drugs.com/article/benzodiazepines.html