Help Converting mg to ml in medication is complicated

[Life interrupted]

Please help. A terminally ill friend wants to exit using the MAID method. He managed go find someone who is ready to sell him propofol but it comes in a bottle of 50ml. He wants to know how to convert that to mg. It's not the simple equation 1mg= 0.001ml. In medication they have another way of converting. Pls help if you know how it's done or know a physician who can help