It works a bit differently. Bioavailability (here 90% for oral) is how much of substance enters your bloodstream. With IV it's always 100%. This now passes the liver (what snorting circumvents) where some drugs are being metabolized (enzymatically transformed into another molecule, active or inactive) and then stuff reaches the brain. Then again liver, next part gets metabolized etc until down to zero. Drugs don't get used up by the body, they act rather like keys in a lock.
This is the usual case. Now with pregabalin only 3% getting metabolized means more of it stays around for longer and can occupy more receptors - this is part of why pregab is more potent than gabapentin. Other is it gets actively transported over the blood brain barrier by some pump.
How the body excrets stuff is another chapter I still have to learn.
But with pregabalin you get no real plus by using other RoA's. With e.g. morphine (poor bioavailability) or ketamine (pronounced first pass = metabolized before reaching the

) things are different.