Tempers flared Tuesday on Capitol Hill as senators from both parties unleashed blistering criticism of pharmacy benefit managers, accusing them of profiteering, monopolistic practices, and systematically forcing independent pharmacies out of business.

Originally designed to help lower drug costs by negotiating discounts with manufacturers, PBMs have come under fire from lawmakers, doctors, pharmacists, and patients who argue they drive prices up by pocketing hidden rebates, steering patients to their own affiliated pharmacies, and reimbursing independent pharmacies at unsustainable rates.