13. Subject must be willing to discontinue applying any topical preparations containing Vitamin A acids (including all trans retinoic acid (tretinoin), 13 cis retinoic acid [isotretinoin], 9 cis retinoic acid [alitretinoin], vitamin A [retinol], retinal, and their derivatives) to the low back starting on the first screening visit until completing participation in the study. Topical preparations containing Vitamin A acids or retinol may be applied to areas of the skin above the waist, but should not be applied to areas of the skin exposed to study medication;