It should be used within a specific timeframe as advised by your pharmacist, typically around 30 days
That depends on your lab results
Its binding to VMAT2 is very strong, making it's effect appear irreversible, with trace amounts of the drug remaining bound to vesicular membranes for many days, and its clinical effects lasting many days to weeks, and may persist until new transporter proteins are synthesized (German et al, 2015
However, for B12, if any part of that complex digestive process is compromised especially the intrinsic factor or the absorption sites in the intestine then a significant portion of the B12 from a tablet might never reach your bloodstream
You need proper technique, sterile supplies, and careful attention to protocol
As a matter of fact, there are a couple of reports now in the literature, believe it or not, demonstrating improvement in goutwhich is generally a situation of high uric acidby doing what's called a fecal microbial transplant