My new dermatologist ordered Carac Fluorouracil cream. My copay was 2.5 times what it would hve been for 5-fluorouracil. Am I paying more for the same thing? (Note: My 5-F was 0.05%, Carac is 0.5%. I can't imagine putting 10X th amt on my skin as I was using with 5-F. Do these numbers really mean Carac is 10X as strong?)