PHARMACY BENEFIT MANAGERS: Requires pharmacy benefit managers to notify contracting pharmacies of changes to maximum allowable costs by the National Drug Code fifteen days prior to the change. Requires pharmacy benefit managers to disclose where an equivalent drug can be obtained at or below the maximum allowable cost, when a maximum allowable cost appeal is upheld on appeal. Requires pharmacy benefit managers to: allow contracting pharmacies to reverse and rebill claims if the pharmacy benefit manager establishes a maximum allowable cost that is denied on appeal; and pay the difference to the contracting pharmacies.