Tretinoin cream increases sun sensitivity so if you are going to use it, you need to be consistent about daily applications of a broad spectrum sunscreen. For someone who has never used hydroquinone before, I would start with 0.025% or 0.05%. Mix a pea-sized amount of medication with moisturizer and apply as you would a lotion to the entire face. Diluting the medication in this way will reduce your chance of developing redness and inflammation that might then create more brown pigmentation. Tretinoin cream should not be used during pregnancy.
Hydroquinone in combination with tretinoin cream can be effective for the treatment of melasma. Hydroquinone can also cause dryness and irritation and can also be used in combination with moisturizer to reduce these effects. I would use no more than 4% hydroquinone. A higher percentage would increase the risk of a condition called exogenous ochronosis in which a permanent blue-black pigmentation can occur. Even 4% hydroquinone can, in theory cause this problem, but less likely (I have never seen a case of exogenous ochronosis with 4% hydroquinone). In laboratory rats treated with hydroquinone, there is an increased risk of tumor development but it is not proven to be carcinogenic in humans. Hydroquinone should be avoided during pregnancy.
Overall, I am convinced of the safety of these medications for myself and my patients. I hope this answers your questions.
Good luck.
