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Research Shows Prescribers Miss Possibly Dangerous Drug Interactions

July 14, 2009

Tucson, Ariz.-Research led by The University of Arizona College of Pharmacy has found that medication prescribers correctly identified fewer than half of drug pairs with potentially dangerous drug-drug interactions.

These findings raise concern because of the high number of drugs Americans take: an average of 2.3 medications is prescribed during each physician office visit.

A synopsis of the research was published in May Research Activities, a digest of research findings intended to contribute to the national policymaking process.

The researchers, led by Daniel Malone, PhD, professor at the UA College of Pharmacy, mailed a questionnaire to 12,500 U.S. prescribers who were selected based on a history of prescribing drugs associated with known potential for drug-drug interaction. Prescribers were primarily physicians, physicians' assistants and nurse practitioners.

Recipients were asked to classify 14 drug pairs as "contraindicated," "may be used together but with monitoring" or "no interaction." Respondents could also state that they were "not sure."

For the drug pairs, one commonly prescribed medication was matched with another commonly prescribed medication.

The 950 respondents classified 42.7 percent of all drug combinations correctly.

Of the 14 drug pairs presented, four of them were contraindicated, meaning they should not be used together. A majority of prescribers correctly identified only one of the four pairs as contraindicated.

Moreover, for half of the 14 drug pairs, more than one-third of the respondents answered that they were "not sure," and two of these drug pairs were contraindicated.

"The study found a very low rate of recognition of these particular interactions," says Malone, "and some of these interactions are very common."

Use of several of the contraindicated drug pairs could be dangerous. For example, taking sildenafil (Viagra®) and nitrates, such as isosorbide mononitrate, can be life-threatening.

According to Malone, the research indicates that health professional programs are not doing enough to teach students about potential drug-drug interactions. Consequently, patients should be sure to tell their pharmacist of all the medications they are taking.

The University of Arizona College of Pharmacy