There is not problem with Cymbalta per se. In other words there is no drug interaction that am aware of. However, since Cymbalta is meant to treat severe depression, I would engage in a thorough discussion with your dermatologist before continuing.
I have used Accutane a few times in patients with clinical depression. But I kept my fingers crossed with each prescription. Each time we were careful to call the patient twice a week to make sure the Accutane was not having an untoward effect. Tell your friends and family to observe you for any signs of depression. Stop Accutane immediatly if you notice any mental changes that are new ( anger, rage, besides depression). As a dermatologist, and to protect myself from legal predetors, I get the treating physician to agree with Accutane as a therapeutic option.
I would feel a little more comfotable with the lower dose, but I did have a patient who developed severe anger issues on 10 mg. ( overweight male).