Depends on the route of action, tizanidine is a STRONG muscle relaxer. Maybe if you can make sure your in a safe place and won't fall over, I.e bed then try 4mg plugged. It hits like a tank that way, I take it regularly, as its the only thing ever that I've found to relieve the constant spasm due to some nerve damage, that I get in my leg. Its really quite agonizing if I don't take it, but zanaflex works miracles on that. I like it for comedowns too. If the first tab doesn't get you out, then the second one sure will if plugged.
Hell no tolerance half that might do you. But on coke I'd go for at least 4mg.