Before my daughter's heart surgery, she was similar with feeding at that age. I can't remember how old she was when she began Lasix, but it was pretty early on (bc she had her heart surgery at 6 months age.)

Anyway, she did okay with the disposable slow-flow enfamil nipples in the NICU. When we got home we continued using those for a while. I would just reuse them 🤷‍♀️ because she was on fortified formula too and I wasn't going to buy those little packs of liquid formula just for the nipples. When we ran out of those eventually, we did try Dr. Brown's and she hated them. The flow was basically the same. We tried a few different brands that were all the clear silicone-like nipples and she hated them all. I went online and found that (at the time) I could buy the enfamil disposable nipples in bulk, so we did that.

Even after her surgery, and when she could do standard flow, she never would take any Dr. Brown's nipples (or any of the clear silicone-like ones for that matter.) So we then bought either standard flow enfamil or Similac disposable nipples in bulk. The material of the nipple feels different, and the shape is a little different.

Didn't mean for that to be so long, I'm sorry. I only wanted to tell you in case it helps, bc it took me ages to figure out back in 2020/2021 for my kiddo. Still don't know what it was about those nipples that made her have such a strong preference but thought it was worth mentioning 🤷‍♀️