The federal government released detailed data today on nearly 1.4 billion prescriptions dispensed to seniors and disabled people in the Medicare program in 2013, bringing more openness to the medication choices of doctors nationwide.

The data release comes two years after ProPublica reported that the Centers for Medicare and Medicaid Services had done little to detect or deter hazardous prescribing in its drug program, known as Medicare Part D. ProPublica analyzed several years’ worth of prescription data, obtained under the Freedom of Information Act, and created a tool called Prescriber Checkup that lets users compare individual physicians to others in the same specialty and state.

But Medicare itself hadn’t made this information easily accessible—until now.

“This transparency will give patients, researchers, and providers access to information that will help shape the future of our nation’s health for the better,” said acting CMS Administrator Andy Slavitt in a statement accompanying the data’s release.

The information released by CMS is part of the agency’s data transparency initiative. In recent years, CMS has released data on hospital charges, geographic variations in the way health care is delivered, and Medicare’s payments to doctors. The payment data, first released last year, came after the Wall Street Journal and its parent company challenged a long-standing legal injunction that had kept the information private.

Medicare changed its approach to overseeing Part D after the ProPublica reports.

Before, agency officials insisted that monitoring problem prescription patterns fell to the private health plans that administer the program, not the government itself. Congress never intended for CMS to second-guess doctors – and didn’t give it that authority, officials said.

Doctors didn’t even have to be enrolled in Medicare to prescribe to patients in Part D, making it impossible for the program to know basic facts about whether the prescriptions these doctors wrote were appropriate.

Since our reports, CMS has moved to fix Part D’s excesses and blind spots. In May 2014, the agency gave itself the authority to expel physicians from Medicare if they are found to prescribe drugs in abusive ways. Beginning next month, the agency also will compel health providers to enroll in Medicare to order medications for patients in Part D, closing the loophole that has allowed some practitioners to operate with little or no oversight.

Medicare Part D is popular among seniors for helping to lower their drug costs. But experts have complained that since Part D began in 2006, Medicare has placed a higher priority on getting prescriptions into patients’ hands than on targeting problem prescribers. The U.S. Department of Health and Human Services’ inspector general has repeatedly called for tighter controls.

Among ProPublica’s findings:

Medicare had failed to use its own records to flag doctors who prescribed thousands of dangerous, inappropriate or unnecessary medications. One Miami psychiatrist, for example, wrote 8,900 prescriptions in 2010 for powerful antipsychotics to patients older than 65, including many with dementia. A black-box warning on the drugs says they should not be used by such patients because it increases their risk of death. The doctor said he’d never been contacted by Medicare. ProPublica also found that many of the top prescribers of the most abused painkillers had been charged with crimes, convicted, disciplined by their state medical boards or terminated from Medicaid. Nearly all remained eligible to prescribe in Medicare.

Medicare wasted hundreds of millions of dollars a year by failing to rein in doctors who routinely give patients pricey name-brand drugs when cheaper generic alternatives are available.

The top prescribers of some drugs received speaking payments from the companies that made them.

Medicare’s process of flagging fraud was so convoluted and ineffective that the program was losing millions of dollars to schemes. Though the number of prescriptions attributed to Florida kidney specialist Carmen Ortiz-Butcher more than quadrupled in a year and the cost of her drugs to Medicare spiked from $282,000 to $4 million, Medicare didn’t ask any questions until Ortiz-Butcher realized that her prescription pads had been stolen and falsified.

The data released by Medicare today includes summary information, such as the total number of prescriptions written by each doctor in 2013, as well as more detailed information about each drug a doctor prescribed. It covers prescriptions worth more than $103 billion, not including rebates that lower the cost by an undisclosed amount.

The top prescribed drug in the program in 2013 was the blood pressure drug Lisinopril, prescribed 36.9 million times, including refills. Medicare spent the most on Nexium, $2.5 billion, not including rebates. The drug taken by the most Part D patients was the narcotic hydrocodone-acetaminophen. More than 8 million users filled at least one prescription for it.

Eric Hammelman, a vice president at the consulting firm Avalere Health, said the prescribing data could unlock clues about differences in how doctors practice medicine. Take, for instance, antibiotics, he said, which are often prescribed for inappropriate reasons. While the new data won’t show which prescriptions are inappropriate, it may flag providers who should be asked questions because they prescribe the drugs to a high proportion of their patients.

Beyond that, if consumers compare the prescribing data to data on the payments drug companies have made to doctors, they can see how often doctors prescribe products sold by companies with whom they have financial relationships.

“Knock on wood, these files are coming out on a regular basis. I think some of the doctors and manufacturers would prefer this goes away,” Hammelman said.

Robert M. Wah, president of the American Medical Association, said in a statement that the data "is much more complex than initially meets the eye. The limitations of it should be more comprehensively listed and highlighted more prominently so that patients can clearly understand them."

ProPublica will be analyzing the information in coming weeks and incorporating the data into our Prescriber Checkup tool.