For anyone who doesn't know what Ultrazine is. It's a drug that only the CL has access to. It makes Marines run at roughly the speed of an Elite Runner.
While that sounds amazing at first glance there are quite bad side effects. The drug will make you addicted even after only 1u and you will need to take more in order to not get withdrawal symptoms. Since there is a very limited supply of the drug needing to take more makes it rather unusable. Withdrawal from the drug will make your character super slow, basically turning the Ultra part into shit. It will also damage your health while not actually damaging anything. So you will go to 70% health without toxin, oxy, brute, burn or organ damage. This damage will disappear once the addiction has worn off. Here is where my research picks up.
I have figured out how to not get withdrawal symptoms from the drug while still getting the positive effects. Here is the research paper I wrote about it.

I made one last test at the end of the round using 10u Ultrazine and 5u Hyperzine but I did end up getting withdrawal symptoms from that lasting around 2 minutes.
I believe the ideal mixture might be something like 7.5/7.5
I need to test this further. But I think this is on a really good track.
Edit: I also ended up getting 2 heart damage but that was after smoking two packs of the stuff at varying strength so I don't consider it even remotely a problem.