PBMs have been systematically underpaying small pharmacies, helping to drive hundreds out of business. The pattern is benefiting the largest PBMs, whose parent companies run their own competing pharmacies. When local drugstores fold, the benefit managers often scoop up their customers, according to dozens of patients and pharmacists. The PBMs' power comes from two main sources. First, the three biggest players — CVS Caremark, Express Scripts and Optum Rx — collectively process roughly 80% of prescriptions in the United States. Second, they determine how much drugstores are reimbursed for medications.
