Gladly
From my perspective based the opinion of an experienced "vendor" and the local Alcohol and Drug Dependency Service who conduct surveillance on this sort of stuff for the purpose of harm-reduction. I suggested it could be possible contain Fentanyl (which has found it's way into all kinds of stuff.) Fentantlyl is often passed off as "pure Heroin".
It’s also roughly 50-100 times cheaper, and at the time was easily obtained as a legal high.
https://www.vice.com/en_us/article/avazbe/why-are-dealers-cutting-fentanyl-into-recreational-drugs
I should add this vendor wasn't the only one with this dodgy speed, it was quite widespread up here for about a year, before the "Spice" epidemic first began to emerge quite visibly and the Psychoactive Substances Act came into force.
Why cut any drug with another drug at all?
Speed from this guy and others in the area was becoming consistently shit, at the time it was less hassle to walk into a headshop or order RC’s online. So maybe some idiot higher-up the cake, thought a sprinkle of a powerful opioid could replace the intense euphoria it was lacking. Vendor took one whiff and was pretty certain there was "smack" in there, he used to peddle it.
Added to a poor quality stimulant, causing users to increase dosage, taken by users with mostly no existing tolerance, a small amount could still be potent.
The mystery adulterant in question was clearly not added for the purpose of bulking. As we know many add Glucose, Caffeine or Sodium Bicarbonate is used to bulk-out. (I have heard one story of someone using Baking Soda as a bulking agent, which turns brown when heated!)
That was the first clue my friend...... Let's call bullshit together.
This particular batch of Speed as a sort of "biscuit" brown colour. I've never seen "speed" that shade, pink sometimes, yellow, even a bit orange but not ever brown. Vendor was told by the source the discolouration was due to it being "an older batch", "not refrigerated properly" but "just as good".
More regular users who'd gone through quite a bit of this "brown speed" (over a few weeks) reported stomach cramps, constipation and the shivers when coming down, and for quite a few days after going back to their normal fix - (non-brown speed). Sounded a bit "cold-turkey-ish". A hard Speed come-down or sudden withdrawal from long term amphetamine dependence doesn't typically present those symptoms.
Buyers reported feeling lethargic, a bit of a rush at first but then spaced-out, dissociated, foggy before going to bed early.
In terms of the warm intense mental and physical effects, Herion doesn’t tend to cause any noticeable rush when ingested, but the additive potential and withdrawal symptoms are still a factor.
Fentanyl on the other hand is pretty administered orally fairly well.
