I can't speak for this drug, but different opioids are processed by different liver pathways. Some people don't properly metabolize something like Oxycodone, b

I can't speak for this drug, but different opioids are processed by different liver pathways. Some people don't properly metabolize something like Oxycodone, but handle morphine just fine. So that's part of it. The other issue is that in specific cases (for instance, in battlefield medicine) you may need something that hits harder and faster than fentanyl. Again, I don't know this particular drug, but it may also last longer than fentanyl, which wears off quite quickly.