Minnesota doctors are again under the microscope of an influential U.S. senator from Iowa -- this time because of concerns that expensive medications are being overprescribed at great cost to the publicly funded Medicaid and Medicare programs.

U.S. Sen. Charles Grassley, R-Iowa, notified federal authorities Wednesday that he found potential examples of overprescribing after requesting lists from states, including Minnesota, of doctors who issued the most prescriptions for antipsychotic and narcotic medications in 2008 and 2009.

The most egregious example, cited in a letter to Health and Human Services Secretary Kathleen Sebelius, was a Florida doctor who wrote 96,685 prescriptions for mental health drugs in 21 months and billed the cost to the state's Medicaid program.

Grassley's letter mentioned no Minnesota physicians, instead pointing out doctors in Ohio, Oklahoma and South Dakota who prescribed many more high-cost drugs than their colleagues to poor and disabled Medicaid patients.

Grassley's findings don't prove fraud or overprescribing, but they could cause doctors to be removed from participating in Medicare and Medicaid, government health programs that, between them, insure some 100 million elderly, poor and disabled Americans. He urged federal authorities to pick up the trail.

"This trend is found again and again across the states," Grassley wrote, "suggesting that top prescribers stand out not only against other providers in their state, but against the very top prescribers in those states."

Last April, Grassley asked Minnesota authorities for a list of 10 doctors who submitted the most claims to the Department of Human Services for prescriptions of such specific antipsychotics as Seroquel and such narcotics as OxyContin.

The state provided the information in May. It also conducted its own review to determine whether the prescriptions appeared appropriate, and whether the top prescribers of antipsychotics were in appropriate specialties, such as psychiatry.

A department spokeswoman said no formal investigations were launched as a result of the review.

None of the doctors on the Minnesota list appeared to approach the excesses Grassley highlighted in other states. Several are on staff at rural mental health centers, which puts them in a position to issue more prescriptions.

Roseville psychiatrist Dr. Roger Johnson stood out on the list, issuing 1,605 prescriptions for Seroquel to patients in Minnesota's managed-care and fee-for-service Medicaid programs in 2009 -- up from 916 prescriptions in 2008. Documents show that his claims to the fee-for-service program alone approached $450,000 last year. The next closest doctor billed the state for just 688 Seroquel prescriptions last year.

An e-mail to Johnson, who retired last month, was not immediately returned regarding his prescribing.

Grassley, a senior member of the Senate's powerful Finance Committee, has made a series of efforts to curb costs and inappropriate medical practices, including investigations of the money that drug and medical device manufacturers pay doctors for lectures, educational seminars and other relationships. His early inquiries started in Minnesota, because it is one of the few states to require drug companies to publicly report their payments to doctors.

Jeremy Olson • 612-673-7744