My daughter has Hyper-Phe and It was a tough decision to put her through a trial of Kuvan. She was only three months old when we tried Kuvan and it worked wonders for her. We do NOT regret the Kuvan trial. Of course, she was very closely monitored every step of the way. She is now 9 1/2 months old and her Kuvan dosage has not had to be adjusted at all. She is doing tremendous! Personally, I would recommend trying Kuvan at a younger age, before they reach the stage where higher protein foods become a part of the picture. This has been a Godsend for our family and we are so thankful that she is responding so well. Her phe level is staying right on target where it is supposed to be, nice and level in spite of dietary changes that are currently happening.
She is hitting developmental and growth milestones even faster than her older sister did (and she is advanced for her age). We have experienced no developmental delays of any kind with her. I realize this is not the case with every Kuvan user. As a Mom, I want the best for my child, and for Hailey, that meant Kuvan. With Kuvan, my daughter is able to live a healthy, fairly normal life that she would not have had otherwise. Her restrictions are minimal and she is thriving. As to side effects, we have not seen any with our daughter but I understand they are minimal.