The tretinoin gel Retin-A's power to force dead cells to shed faster make it a popular medication to treat acne, but according to Health.ucsd.edu, side effects include excessive drying and peeling of the skin. Mixing a moisturizer with Retin-A is fine as long as you make sure the medication has an adequate chance to penetrate your pores.
Mix a dab of lotion with a dab of Retin-A and then apply if you find your skin severely drying out. This will reduce the amount of Retin-A you use while giving your skin some moisture. Make sure the moisturizer is oil-free so it won't clog your pores. Also be aware there is a possibility the Retin-A will have a harder time getting into your skin if it has to go through a layer of lotion first. Use only non-comodegenic moisturizers that are made for facial skin. Lotions that contain perfumes can burn skin, especially if it is already sensitive from the effects of Retin-A.
Wait at least 30 minutes after applying Retin-A before you use a moisturizer. This will allow the active ingredients in the Retin-A to completely penetrate your pores. For even better results, if you apply your Retin-A at night, wait until the morning to moisturize so the Retin-A has ample time to get into your pores. Gently exfoliate before you apply your moisturizer, but only if you are not directly following a Retin-A application. The lotion won't be able to do its job if it has a layer of dead skin to penetrate before it can get into your pores. Using a washcloth to rinse the cleanser off your face is an easy way to remove dead skin without being too rough on the already sensitive areas. Use a moisturizer with an SPF during the day. Retin-A makes skin more sensitive to sunburns, so protecting skin with an SPF is imperative. If you're going to be outside for a long period of time, use a higher SPF and reapply frequently. You may also want to consider rearranging your Retin-A application schedule so you're not putting it on your skin the night before you're planning to be outside for an extended period of time. Moisturize as often as you feel you need it.