May 20 (Reuters) - UnitedHealth said on Monday its unit OptumRx would offer a new pricing model, starting next year, to help manage insurers' costs for drugs.

The new model, Optum Rx Clear Trend Guarantee, will provide value-based pricing of drugs per member combining the cost of these medicines from various sources such as retail pharmacy, home delivery, specialty drug and rebates.

Under value-based pricing models, insurers, pharmaceutical companies and the middlemen, which include pharmacy benefit managers (PBMs) like OptumRx, agree to link payment for medicine to the overall outcome for patients.

The new model adds to OptumRx's announcements of other measures to offer transparent pricing of drugs last year and comes amid increased scrutiny into the role of PBMs in ballooning healthcare costs in the United States.

Currently, out-of-pocket drug prices are decided by a complex, multi-tiered network including insurers, drugmakers, pharmacies and PBMs, resulting in ambiguity around fees and markups to the original cost of the drug.

PBMs handle prescription drug benefits for health insurance companies, large employers and Medicare prescription drug plans — a group often referred to as payers.

OptumRx's new model will be effective at the same time as TrueCost, which was announced by CVS' PBM unit, Caremark, to offer clients more visibility into prescription drug pricing and administrative fees. (Reporting by Sriparna Roy in Bengaluru; Editing by Shilpi Majumdar)