UnitedHealth Group's OptumRx is buying Diplomat Pharmacy for $300 million

UnitedHealth Group's OptumRx division is buying Diplomat Pharmacy for $300 million, roughly a month after Diplomat said it was running out of money and was exploring a sale.

Why it matters: Health insurance companies have tightened their oligopoly hold on specialty pharmacies.

• UnitedHealth and the other big insurers, which own these pharmacies that sell high-cost drugs for complex diseases, helped create Diplomat's financial problems by routing prescriptions to themselves over Diplomat. 
• Now, Diplomat is selling itself to the giant that squeezed it, at a discount, and specialty pharmacy competition goes down. Diplomat's pharmacy benefit manager also gets absorbed by UnitedHealth.

Go deeper: 

• Why specialty pharmacies matter
• The fall of a major specialty pharmacy