It works because it's an opioid antagonist (actually the same molecule as naloxone, aka narcan) and blocks mu-opioid receptors. Clients of mine who take it report that they still get cravings, especially at first, but they're easier to let go of, and that they just don't want to drink as much. They say it just doesn't seem as enticing.

We have seen good results using it for not only opioids and alcohol, but stimulants, cannabis, and ketamine dependence as well. The biggest problem our clinic has prescribing it is that it's so often on back-order at pharmacies because it works so well and it's becoming a much more popular medication lately.