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Study warns on use of 2 common drugs

Says combining pair can raise blood sugar

By Chelsea Conaboy
Globe Staff / May 28, 2011

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Combining two drugs commonly prescribed to treat depression and lower cholesterol can raise blood sugar to potentially harmful levels, according to a study released this week that was based partly on a search of computerized patient records at Boston-area hospitals.

The side effect — which the authors said could push glucose-intolerant people into a diabetic state or make existing cases of diabetes harder to manage — was unexpected, and its discovery illustrates the power of electronic health records to help bring to light previously unknown problems with medical treatments.

The results of the study, published in the journal of Clinical Pharmacology & Therapeutics, are significant: The authors estimate that as many as 715,000 people may be taking the two drugs, paroxetine and pravastin, marketed as Paxil and Pravachol. But perhaps more notable are the methods used.

Researchers at Stanford University identified the drug combination as a possible concern by combing a massive Food and Drug Administration data base of side effects for signs of diabetes-related drug interactions. They quickly and cheaply tested their theory using hundreds of thousands of electronic health records for patients at Stanford University Hospital, Vanderbilt University Medical Center, and the hospitals of Boston-based Partners HealthCare.

Doctors and hospital systems are under pressure to adopt electronic health records by 2014 or face penalties through reduced Medicare and Medicaid payments. Much of the public conversation about the technology has focused on the billions of dollars in upfront costs needed to install them and the potential long-term savings.

But the new study offers a peak into the “totally unprecedented’’ research potential of such large, sophisticated patient databases, said Dr. David Blumenthal, former national coordinator for health information technology who recently returned to his posts as a professor at the Harvard School of Public Health and a physician at Massachusetts General Hospital, a Partners hospital.

The electronic records make it possible to study a whole population of patients in real time, “in the wild, so to speak, as we are cared for, because that’s the most realistic study sample,’’ said Dr. Isaac Kohane, an author of the study and codirector of the Harvard Medical School Center for Biomedical Informatics. “You can come in with a question and literally, in weeks rather than years, answer important epidemiological questions.’’

Nicholas Tatonetti, a doctoral student at Stanford, developed algorithms to search the FDA database, looking not for specific reports of an increase in blood sugar but for the associated symptoms, including fever and fatigue. He came up with a list of possible problematic combinations. When his adviser, Dr. Russ B. Altman, looked at the list, pravastatin and paroxetine jumped out at him. He knew they were each used by millions of US patients.

“I said, ‘Wow, if that’s real, that’s a big deal,’ ’’ Altman recalled in an interview.

But the FDA database is so big and so messy that it often produces false results, Altman said. If validating their concerns required scouring paper records — like those still used by many doctors — or enrolling patients in a costly clinical trial, his lab never would have pursued it, he said.

Instead, the researchers searched the Stanford hospital electronic records for a specific kind of patient, one who had started one of the drugs and had a glucose test, then started the second drug and had another glucose test. They found nine non-diabetic patients who fit the bill.

They reached out to colleagues at the other two institutions who found another 127 non-diabetic patients, the bulk of whom came from Partners hospitals. Overall, the patients taking both drugs experienced an average increase in glucose of 19 milligrams per deciliter after starting on the second drug, and the increase was much greater among 239 diabetic patients taking both medications.

A spokeswoman from the FDA declined to comment on the study, as did those at GlaxoSmithKline, maker of Paxil, and Bristol-Myers Squibb, maker of Pravachol. Altman, who sits on an FDA advisory board, said he hopes the study will catch the attention of regulators and pharmacists.

The authors stressed that more studies are needed on the two drugs and they cautioned that the glucose tests were not controlled for what a person may have eaten that day.

Patient names were kept confidential by the researchers, but they said privacy concerns will have to be addressed before such studies become more common. And Blumenthal cautioned that the results of quick database searches like this can often be wrong. Still, he said the research gives a glimpse of the public health implications as the nation’s health system becomes more digitized.

“Given the power of computing, you can do this study in minutes if you’ve got a big structure like this,’’ Blumenthal said. “You could do 100 studies in an hour instead of doing one study in a year. . . . And, by the way, you can do this not just with drug events. You can do it with the relationship between treatments and symptoms. You can track the spread of an influenza event.’’

Chelsea Conaboy can be reached at cconaboy@boston.com.