A dermatologist wishes to process the French speciality Locacid in a cream with prednisolone and hydroquinone. However, the concentration of Locacid should be halved to 0.025%. Which basis can I use?

Locacid contains Tretinoin. I   would use an emulsigel consisting of: Hydroalcoholic Carbomeergel FN 6 79 G and Cetomacrogol cream 21 G. This cream should contain 50 mg of BHT and 500 mg of nametabisulfite for the stabilization of Tretinoin and hydroquinone.