Drugmakers limiting discounted prescription sales to some pharmacies participating in a federal program intended for safety-net providers could pressure profits at the largest pharmacy benefit managers. 

Congress developed the 340B drug discount program in 1992 to offer hospitals that care for large numbers of low-income and uninsured patients big drug discounts, with the intent that participating  hospitals will reinvest the savings into charity care. Cancer centers, children's hospitals, rural providers and other hospitals often contract with outside pharmacies to fill 340B prescriptions for patients. Altogether, about 2,600 hospitals participate in the program.

PBMs profit from the program by steering patients to pharmacies owned by the same parent company as them and by charging providers referral and dispensing fees for filling their patients' prescriptions.