Hydroquinone and Ochronosis For Skin Lightening?

I have olive complexion. My doctor presribed a custom formula for skin lightening containing Hydroquinone 8%, tretinoin .1%, hydrocortisone .5%, and clindamycin 1%. I read on the internet about skin darkening (ochronosis) with hydroquinone use. I would like to try using the presription but am worried about this side effect. How likely is it to happen? Are there steps to prevent this from happening like using it intermittently once I have acheived a good skin tone? Taking breaks, etc? Thank you!