Profs study prescription drug hazards

Ever pop a Paxil with your Imitrex?

Even if you don't know the two medications shouldn't be taken together, at least your doctor has received a letter about it.

In the Sept. 17 issue of the Journal of the American Medical Association, researchers led by Epidemiology Professor Sean Hennessy reported their finding that notifying physicians of potential drug interactions does not alter doctors' prescription habits.

The study, which followed Medicaid patients in six states for a period of four years, revolved around the Drug Utilization Review mandated by federal law, Hennessy said. In the early '90s, the legislation authorizing the DUR was passed, requiring states to check each Medicaid patient's prescription for potential interactions with other medications, as well as to determine if cheaper options are available. If anything is found, doctors are sent a letter, he explained.

In theory, the DUR is supposed to work in two ways. Its "direct" impact is to change the physician's treatment of the individual patient. A "spillover" effect is also supposed to occur as doctors recognize the problems in other patients and adjust their medication choices accordingly, Hennessy explained.

But by tracking the rates of hospitalization due to drug interactions as well as studying overall prescription habits, Hennessy and his team found no change in trends that existed before the DUR, he said. This indicates that the theoretical goals of the DUR are not being reached.

"The programs seem like a good idea, and those running them are doing them for the right reasons," Hennessy said. "The problem is that they were never systematically tested before being implemented."

"I think the work is very solid," said Albert Wertheimer, director of the Center for Pharmaceutical Health Services Research at Temple University.

Despite flaws in the current system, "drug surveillance needs to be done," he said, adding that more research is needed.

A variety of reasons could account for Hennessy's findings.

Doctors "might not read the letter," Hennessy said, noting that physicians get hundreds of letters every day. Additionally, by the time the letter arrives, the patient may have already had the problem.

Other doctors may have known about the potential drug interaction hazard but believed the potential benefit to be worth the risk, he added.

Some physicians may also question the experts' drug risk calculations.

"We don't really know which drug interactions will have an impact and which ones won't," Hennessy said, noting that most of the guidelines are generated through chemistry theories. Consequently, what constitutes a potential risk can vary from expert to expert.

Most pharmacies have computerized drug utilization reviews that give an instantaneous result, said a CVS pharmacist, who asked not to be identified.

While pharmacists call doctors and tell patients about potential problems "every time... most cases are very benign" -- and doctors tell the pharmacist to prescribe the drug anyway, he said.

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