Seven years after a U.S. senator cited him as a national example of aberrant practices, the onetime top prescriber of antipsychotic drugs in Florida’s Medicaid program is in federal custody awaiting sentencing on fraud charges.

The second-highest prescriber is serving a four-year term in federal prison after pleading guilty to fraud charges in 2012, but he only relinquished his license to practice medicine in Florida last fall.

Taken together, the cases illustrate how long it can take regulators and law enforcement to take action against problem doctors — and how those physicians can continue prescribing drugs paid for by taxpayers in the meantime. In 2011, ProPublica wrote about the suspicious prescribing patterns of the two Miami-area psychiatrists, Fernando Mendez-Villamil and Huberto Merayo.

Questions about the doctors’ prescribing were first brought to light by Ken Kramer, a private investigator in Clearwater, Florida, who runs a website that compiles public records on psychiatrists. He complained to Florida’s Medicaid fraud unit in 2007 that Mendez-Villamil appeared to be prescribing a disproportionate amount of the antipsychotic Abilify to children.

“Talk about slow justice,” he said in an email to ProPublica, when sharing news that Mendez-Villamil pleaded guilty in May to an array of federal charges.

Prompted, in part, by the information Kramer gathered, Sen. Charles Grassley, R-Iowa, pressed Medicaid directors in all 50 states to explain how they were monitoring top prescribers of antipsychotics, narcotics and other risky drugs. He also demanded a list from each state of the top 10 prescribers of eight drugs and whether any action had been taken against them.

“When I started looking at top prescribers a few years ago, there was a frustration that state and federal authorities were slow to look at the problem,” Grassley, who is now chairman of the Senate Judiciary Committee, said in an email to ProPublica. “That has to change. Patients are served badly by doctors who commit fraud.”

Mendez-Villamil wrote more than 96,000 Medicaid prescriptions for mental-health drugs from July 2007 to March 2009, more than any other physician in Florida, according to a document released by Grassley at the time. In 2009 alone, he prescribed about $4.7 million in antipsychotics to Medicaid patients, other records showed.

Documents showed that Florida had known since at least 2004 that Mendez-Villamil was a problem, but did not bar him from billing Medicaid until 2010 after Grassley made his prescribing record public. Even then, it terminated him officially “without cause,” a fast way of removing a doctor from the program, but without subjecting him to disciplinary action by other states or the federal government.

In 2013, he was reprimanded, fined and ordered to take a class by Florida’s medical board.

After he was terminated from Medicaid, though, Mendez-Villamil continued prescribing drugs to patients in Medicare, the federal insurance program for seniors and the disabled. From 2011 to 2013, the most recent year for which data is available, he wrote nearly 47,000 prescriptions worth more than $6 million in Medicare’s drug program, called Part D.

In a letter to Grassley in 2010, Mendez-Villamil wrote that his prescriptions were justified by his busy practice. And in a 2011 interview, his lawyer said he was “collateral damage” in Grassley’s campaign.

Last month, Mendez-Villamil, 49, pleaded guilty to felony charges of conspiracy to commit health care fraud, conspiracy to defraud the government by making false statements with respect to immigration matters, and conspiracy to defraud the government with respect to claims. He admitted to lying on immigration forms to help people skip English and civics tests needed to become citizens and helping people fraudulently obtain Social Security disability benefits. The doctor agreed to forfeit more than $30 million. He is in federal custody as he awaits sentencing next month.

Merayo, 64, ranked second for prescribing mental-health drugs in Florida Medicaid from July 2007 to March 2009. In 2009 alone, he prescribed nearly $2 million worth of antipsychotics to Medicaid patients.

In 2011, Florida summarily ended his Medicaid contract, also “without cause,” after a state review found he hadn’t documented why patients were prescribed the antipsychotic pills and had given them to patients with heart ailments or diabetes despite label warnings.

At the time, his lawyer said the doctor had not been advised of any allegations of billing irregularities.

In 2012, federal prosecutors charged Merayo with health care fraud for signing medical diagnosis and treatment forms “knowing that the patients he was supposedly treating and supervising the treatment of did not qualify for the services he purported to provide.” He agreed to plead guilty the same day. He was sentenced to four years in prison in 2013 and ordered to pay $6.7 million in restitution.

Like Mendez-Villamil, Merayo continued prescribing in the Medicare Part D program after he was terminated from Florida’s Medicaid program. From 2011 to 2013, he wrote 22,460 prescriptions, worth almost $2.5 million. More than 1,200 of those prescriptions were attributed to him in 2013, months after his guilty plea.

Florida’s medical board does not appear to have taken action against Merayo based on his conviction. Instead, in 2015, it accused him of medical malpractice and other wrongdoing related to his care of two patients on psychotropic medications. In addition to relinquishing his license last year, he agreed to never reapply.

Florida’s Agency for Health Care Administration, which runs Medicaid, said in a statement that it now uses data analytics and audits to examine prescribing outliers. But because Medicaid services are now predominantly delivered through managed-care plans, that shifted “the principal oversight and management duties to the contracted managed care plans and their anti-fraud units.”

The doctors could not be reached for comment. An attorney for Mendez-Villamil, Jorge Viera, declined to comment because his client has not yet been sentenced.

The Centers for Medicare and Medicaid Services, which is in charge of Medicare and Medicaid, also declined to discuss the specific cases but said it is working to ramp up its fraud fighting efforts.

CMS also is trying to compel health providers to enroll in Medicare to order medications for patients covered by Part D. That would close a loophole that has allowed some practitioners to operate with little or no oversight from Medicare.

But Medicare has pushed back the effective date of this requirement twice now, from June 2015 to next year. Until prescribers are required to enroll in Medicare, it’s harder for the program to take actions against those who prescribe in abusive ways, said Shantanu Agrawal, director of CMS’ Center for Program Integrity.

“Right now, we can analyze a lot of data in Part D because we do have good access to data but without that enrollment lever [the ability to terminate abusive prescribers], we are not able to take as many actions,” he said.

Agrawal also said CMS is working with states to ensure that when a provider is terminated by a Medicaid program for abusive prescribing, that the action be labeled as such and not as a “without cause” termination, as happened in the cases of Mendez-Villamil and Merayo.

Terminations for cause prompt other states to act, while those without cause do not, he said. “I think it’s extremely important that we label these cases the right way,” Agrawal said.

For his part, Grassley said he hopes Mendez-Villamil’s case will serve as an example of how all those involved can improve. “State and federal prosecutors should use this high-profile case as an example of how to use data for the public good,” he said by email. “If someone is writing more prescriptions than seems humanly possible, that’s a red flag for fraud and potential harm to patients. It pays to investigate, and time is often of the essence.”