- Other: At least 4 weeks since any prior investigational medications At least 4 weeks since any prior systemic therapy, such as hypolipidemics or retinoids Nonglycerin emollients allowed up to 1 week prior to study At least 4 weeks since any other topical therapy including humectants such as urea, alpha hydroxy or alpha ketoacid preparations and retinoids No concurrent topical therapy No concurrent investigational medications