Allow me to answer this for you.
I had a friend you injected Xanax a couple years ago, he did it several times a day, swore it kicked in quicker (I'm sure, considering it's directly into your bloodstream) but he dissolved it in everclear (190 proof/90% alc/vol) and then injected it once he dissolved a couple 1mg Xanax PILLS into the alcohol.
I watched him after he injected it and was with him, he wasn't overly fucked up, didn't claim a rush, and honestly he liked to exaggerate things to begin with.
It was pointless. I ate my Xanax while he shot his and I got just as high, if not higher. The injection did nothing special except maybe get into his system a bit quicker, but I'm telling you first off, alcohol and benzos shouldn't be mixed for obvious reasons. Plus oral Xanax is SO quick acting anyway. Hits most within 5-20 minutes.
Additionally, the ORAL Bioavailability of alprazolam is 80-90%, and I'd lean more towards the 90% end of the spectrum with most people. Meaning, via IV you might get from 90% of the medicine in your body to 100%. It's just not worth it. Whereas, the oral bioavailability of a med like dilaudid (hydromorphone) is only 30%, IV use has it's obvious advantages. With that, it's like throwing away 5.6mg of an 8mg dilaudid if you were to eat it.
Also, DONT fuck with "what you think is pure" alprazolam powder. The shit is strong as hell in pure powder form and and a finger dab or IV shot could black you out very substantially for a while. It's dangerous. Do some more research.
All in all, I'd suggest getting an expensive scale accurate to 0.001g to weigh out oral doses, and honestly that's about all I'd "suggest." It's just not a good idea and I am in no way trying to be direspectful. Trust me there was a day when I thought shooting Xanax would be worth it, but when you look at the fact that almost no one reports a rush from IV benzos like Valium or Ativan, except Versed (midazolam), that shows you something. Benzos just have a really high oral BA and should be taken as such.
As a benzo connoisseur, I can tell you that the oral route is easiest, most efficient, and the least rough on your body.
LAST but not least...NEVER inject a solution (although not a SOLution because clearly it's not all dissolved) that had particles left in it. This is why Heroin IV Users use cotton to filter the cut/adulterants from their shot.
Be careful and good luck you have a valuable substance (alprazolam powder), but doing something safely with it is your next challenge.