The federal government is suing some big pharmacy benefit managers over a system of drug rebates that regulators say has made the price of insulin soar for diabetic patients. Three companies that process about 80% of prescriptions in the United States — Caremark,

The case takes aim at the major pharmacy benefit managers, agency officials said, claiming that they favored more expensive insulin products and forced patients to pay more.

Pharmacy-benefit managers owned by CVS, Cigna and UnitedHealth “artificially inflated” prices for lifesaving medications, regulator alleges.