Do we build up a tolerance to anti-depression/bipolar meds?

Hi Andy. Yes, that is absolutely possible. A friend of mine has been on an antidepressant, and all of a sudden it just stopped working. She went to her doctor, and was told that could happen, so he had to add another medication to it, and then she felt better. I went through the same thing with my anxiety medication. It helped for a while, then when my body got use to it, i had to keep taking more and more, because it would stop working. And about surgery, it can affect the way your body reacts to medication. Having surgery stresses your body, and you usually need to take a higher dose of medication to compensate for that. I've been in that situation also, and it happened to me. Take care.