I routinely use hydroquinone on all Fraxel patients who have darker skin tones and are more likely to tan than burn (Fitzpatrick scale IV-VI). The reason for this is to minimize the risk of hyperpigmentation (or darkening of the skin) after the treatment. As a result, I've been able to keep my rate of hyperpigmentation after Fraxel very low. I do use Kojic acid derivatives for other reasons in my practice, but not as a replacement for hydroquinone. I don't believe there is any good scientific data comparing them, but Kojic acid is a lot weaker skin lightener than hydroquinone.
In terms of timing, I have my patients start hydroquinone one month before Fraxel, twice a day, and then stop it 5 days before the Fraxel. They resume it 5 days after Fraxel and continue on that protocol until all the treatments are done. Good luck.
