The only true way would be to take the entire thing (the whole gram and 10mg of fent) and make into a liquid. I would just get a mg scale and test every batch that you make, meaning if you think you have measured out 100ug into a shot, I would do less than half and wait. when my wife would get shots of fentanyl they would give 50ug shots and she was a little opiate tolerant, but she was flying on that small amount. This stuff is too dangerous to mess with if you don't know what you are doing. I am very experienced and I still would be nervous. Maybe get a bottle of narcan on hand. Go to a vets office and tell him that your afraid that your dog will get into your pain pills. Ive personally administered it and its amazing, they pop out of it like nothing happened. (used to be a paramedic, thats why im so anal about Harm reduction. Ive seen way too many od's that could have been prevented)