The figures come out to 4.9 million monthly Medicaid prescriptions handled by Managed Medicaid plans (MMCs) in 2011 compared with 12.5 million in 2012.
The study attributed the shift to states that are "seeking cost savings and improved preventive care" not afforded by the traditional fee-for-service model.
Under a managed care model, companies receive a bundled payment for each Medicaid enrollee that is determined by a contract with the state. Supporters say this approach saves money, facilitates care coordination and delivers better outcomes for patients.
Thursday's study analyzed Medicaid in four states — Kentucky, New Jersey, New York and Ohio — and concluded that beneficiaries in Managed Medicaid experienced some differences in care. Patients saw a greater use of generic antipsychotic drugs compared with brand-name ones, for example.
In New York, they used more medications for diabetes, and in Kentucky, more respiratory medications.
Murray Aitken, executive director of the IMS Institute, stated that more research should be devoted to how looming shifts within the Medicaid program affect patient care.
"Prescription drug usage is typically an indicator of effective overall disease management, particularly in chronic diseases," he wrote.