I am on one right now (prescription). It is a category C, but I was assured by my OB and pharmacist that it was fine in third tri and especially in very small amounts like I need.
I don't even like to take Tylenol and have had to have several prescriptions over the past 6 weeks due to an issue I am having (they keep trying different things). I feel blessed to have access to meds, but I hate going through this as I really wanted to have nothing the whole time! But again, things that are no-nos in first tri can sometimes be ok by third depending on what they are.