I took my first course of Accutane at 19 and it was tremendously improved. Life changing to say the least. It seemed to come back again 3-4 yrs later and I took another full course. This happened again at 3-4 yrs later after the 2nd course and I needed it a 3rd time. Now 6 yrs later I've noticed my acne returning. I'm using salicylic acid, Retin A and nothing improves it. My skin has never responded to topical tx. My acne is minor but doesn't respond to tx. Is a 4th course of Accutane safe?