Co-pay coupons for prescription drugs could drive up costs to employers, unions and state governments by $32 billion over the next ten years, said the Pharmaceutical Care Management Association, the pharmacy benefit managers’ trade group.

In the State of New York, the coupons will cost employers, unions and state employee plans an extra $2.3 billion over the next decade and cost state taxpayers an additional $379 million, said a study by healthcare consultancy Visante for the PCMA.

Medicare and Medicaid are off-limits to the coupons, which are considered as illegal kickbacks by the feds, but outside of Massachusetts, they’re perfectly legal in the commercial market. If the federal ban on the use of couponing were not enforced, the study found, costs to the Part D prescription drug benefit would jump by $18 billion over ten years. If allowed in Massachusetts, costs to employers and other plan sponsors in that state would rise by $750 million for the same period.

“Copay coupons are designed to undermine generics, increase sales of more expensive brands and stick employers with the tab,” said PCMA president and CEO Mark Merritt in a statement.