A local law firm is pressing ambitious class action suits against insurers Cigna and UnitedHealth, accusing the health care giants of cheating customers by imposing prescription co-payments that often exceed the entire cost of prescription drugs.

The suits by the West Hartford firm Izard, Kindall and Raabe assert that insurers orchestrated a fraud that bilked tens of thousands of insureds out of millions of dollars in unjustified prescription benefit costs.

The Cigna suit was filed Thursday in federal court in Connecticut on behalf of a single policy holder. Three United customers brought a similar suit against United earlier this month in Minnesota. The law firm is seeking to have both suits certified as class actions.

The allegations against both insurers are essentially the same: They are accused of charging co-pays that, in the cases of dozens of widely prescribed drugs, are double or more than cost of the entire prescription. In one case, the suit claims, a Cigna health customer paid a co-pay that was more than 1,000 percent greater than the cost of the prescription.

The suit contends that customers are not making the “co-payments” required by their insurance coverage, but rather are making “you-payments.”

“We have received complaints from all over the country that customers are overpaying for prescription drugs,” said Craig A. Raabe, one of the lawyers whose West Hartford firm filed the suits. “This lawsuit is to end the overcharges and get reimbursement for the customers.”

Cigna said it does not comment on litigation. UnitedHealth did not have an immediate response.

Prices to be paid for prescription drugs typically are negotiated between health insurers and pharmacies. Businesses called prescription benefit managers act as middlemen in the transactions that actually deliver drugs to customers.

Although the benefit managers are not named defendants in the suits, they are described as complicit in a system that forces pharmacists to charge customers unjustifiably high co-pays. Under the terms of their agreements with the benefit managers, the suit contends pharmacists are obligated to return excessive costs to the insurance companies.

The suit refers to what it claims was a 2014 transaction in which a Cigna customer paid a $20 co-payment to his pharmacy to purchase the drug Amlodipine – a co-pay that was 1,043 percent higher than what Cigna and the pharmacy had agreed was the cost of the drug.

Cigna had negotiated a price of $1.75 for the Amlodipine prescription, according to the suit. The pharmacy, by agreement, was permitted to keep $1.75 of the $20 co-payment and obligated to return the remaining $18.25, known as “the spread,” to the insurer. The suit claims the delivery of the spread to the insurer is known in the industry as a “clawback.”

The suit claims that the insurers are engaged in a continuing conspiracy to defraud their customers in violation of both the federal Employee Retirement Income Security Act of 1974 and the federal Racketeering Influenced and Corrupt Organizations Act.