(a) Subject to Subsection (b), the commission shall negotiate with manufacturers and labelers, including generic manufacturers and labelers, to obtain supplemental rebates for prescription drugs provided under:
(1) the Medicaid vendor drug program in excess of the Medicaid rebates required by 42 U.S.C. Section 1396r-8;
(2) the child health plan program; and
(3) any other state program the commission or a health and human services agency administers, including a community mental health center or state mental health hospital.
(b) The commission may by contract authorize a private entity to negotiate with manufacturers and labelers on the commission's behalf.