Medicine question

I called my pharmacy but they were not very helpful. I displaced a rib and while it’s healing it’s been so so painful. I went to the chiro yesterday to have it replaced and today, holy wow 😩 it hurts so breathe and picking up my baby is impossible.

I’ve taken Tizanidine before for muscle injuries and know I respond well to it. The problem is I’m breastfeeding and this is one of those medications that really hasn’t been studied. It’s a class C drug, so there are possible risks to baby they just can’t say for sure. I called the pharmacy and they basically told me it’s up to me.

I would rather play it safe, and just dump the milk while I have the drug in my system. So here’s my question for anyone that knows more about drugs than me: If it has a half life of 150 mins, would it be totally gone within like 5 hours or so? Or is that not what the half life thing means?