Except as otherwise specified in this section, if an enrollee chooses to have a prescription filled with a brand name drug when a recognized generic drug is available, a copayment is required. For the initial year of operation, the copayment amount is $15.00. For subsequent years, the amount of a copayment applied under this section may be established by the legislature. Nothing in this section shall be construed as allowing therapeutic substitution. The department shall develop a mechanism, with the advice of the advisory committee established in section 7, that will specify when drugs should be dispensed as written and not subject to the $15.00 copayment. These recommendations shall be presented to the senate and house of representatives appropriations committees not later than September 1, 2001.