As has already been said, it does not dissolve freely in alcohol that is 40%abv (I.e vodka) or lower (sometimes vodka is 37.5%). At the concentrations we're talking about (from personal experience) it won't precipitate out of PG, and as it's a lot cheaper than buying high % alcohol, it's the more viable option.
In regards to IV - As also mentioned (I believe by pbuilder, sorry I'm replying on my phone hence why quoting furryfreek fucked up also) something I forgot is you ~must~ use sterile equipment when preparing the solution. I do not know much about IV or slow drips, so do plenty research before attempting this, don't take my word as gospel - but I believe there is information on it somewhere (perhaps check the etizolam megathread) where there is a chap who does IV the solution, but mixed with sterile water, as IV PG solution alone can harden your veins (I know this wasn't what you planned to do, just a heads up). I believe this works because the etizolam is already dissolved into the PG.
On the other hand, I wouldnt advise IV etizolam - my tolerance skyrocketed jjust switching to oral solution!
I guess all I'm trying to say is, please be careful

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