Based in the UK I started Hydroxyurea when I was 19 years old and it changed my life for the better, a wonder drug indeed. I went from transfusions once a month and a crisis 6 to 7 times per year to nothing but Hydroxyurea. No side effects. Started doing all the things I couldn’t before, weights, swimming, business secondments, all because of Hydroxyurea. 25 years later and I’m on the exact same dose as day one, 500mg and 1000mg alternating.
The ONLY bad side of Hydroxyurea in my case, not sure about others, is that it makes me infertile while I’m using it so family planning has been an absolute nightmare resulting in us only having one child (a blessing in itself). This was never disclosed until we mentioned having problems. Having stopped Hydroxy, 3 weeks later I was in hospital with a crisis but 4 months later my Wife was pregnant. This is the only but significant side effect of an otherwise brilliant drug.