Mont. Code Ann. § 33-22-176
Limitation on copayments
33-22-176 . Limitation on copayments. A pharmacy benefit manager or third-party payer may not charge a patient a copayment that exceeds the cost of the prescription drug. If a patient pays a copayment, the dispensing provider or pharmacy may retain the adjudicated reimbursement and the pharmacy benefit manager or third-party payer may not alter the adjudicated reimbursement.