injecting magnesium sulphate does have a noticable effect, it seems to be a combination of an overflowing/rushing sensation in the head and a heat rush in the lower abdominal region. Different salts have different effects, sodium chloride, for example makes your head feel quite hot and raises overall body temperature. All of these effects are caused by a temporary and massive jump in concentrations of these ions, which facilitate certain kinds of nerve signals. Magnesium in particular would be synergistic with methamphetamine as magnesium is critical to rapid and focussed transport of nerve signals.
I used to find that the combination of the yellow crank shite that was cut about 1:10 with magnesium sulphate (it was often a bit wet looking from the HI salts i'm guessing), it gave this MASSIVE headrush, it was like the most utter mindnumbing blast of ecstasy, me and my friends used to often spend the first 20 minutes so overwhelmed by the intensity of the rushes we could barely speak...
i think that's why so many people get so addicted to that particular type of gear, the rush is something i would think to be similar to the headrush from cocaine, maybe not the same, but similar in intensity and duration. There was also often a massive dropoff to a very painful comedown at about 3 hours into it... evil nasty comedown, which i found a mind trick to stop it being painful
oddly enough it was like the negative thoughts, thoughts involving resistance or distaste - and this applied to the pain itself as well, compounding on itself seemed to directly turn from a vaguely negative thought into an ache somewhere - but there seemed to be a way of turning them around by just accepting them rather than feeling some kind of distaste or annoyance. doing this caused me to have an immediate headrush and intense feeling of bliss. It was this that caused me to continue my interest in these compounds... pure material does not affect me the same way, however that's probably a good thing.... i can't really say... but i can say that the yellow cut crank would have killed my liver and kidneys slowly but surely if i kept using it.
okok i'm digressing. in conclusion, my experience shows that magnesium is mildly active with regard to causing headrushes, and this, combined with the effects of unreacted pseudo and iodoephedrine and p2p causes a very intense but short lived rush when injected. glucose is another common cut, and it will cause a rush too, and a converse crash which will compound with the amphetamine come-down.
cutting agents suck