Your best bet for dosing is don't ever do even one injection of that shit. It is as addictive as heroin. How do I know? I am very close to some people who after they took their first shots of the stuff felt great and didn't stop for over 3 years. Their dosages got up to as much as 20-30 ampules/day ( approx. $2000 worth/month). Their usage only stopped after a few trips to rehab. The emotional and financial burden may never be recovered for these individuals.
Please, please, please don't ruin your life with it. You will end up slipping into a very deep, dark, dirty hole with no way out.
Best wishes to you.
PS - If you are in pain please see a doctor so he can monitor your pain management.