Drug-Drug Interaction Initiative to provide pharmacists with reliable drug interaction messaging

Whenever you pick up a prescription at your community pharmacy, the information is entered into a computer database, which immediately checks the new prescription against your current medications and alerts pharmacists about possible interactions between drugs.

However, these warnings sometimes can be redundant, irrelevant or outdated, causing concern among pharmacists, patients and researchers. Pharmacists are faced with sorting through many possible interactions to determine which ones are important and likely to occur.

In order to address this ongoing problem, the United States Pharmacopeia (USP) began the Drug-Drug Interaction Initiative (DDII). Its goal is to provide pharmacists with reliable drug interaction messaging, based on new industry standards for evaluation of interactions.

The development and testing of these new standards is very important, because currently the relative significance of some drug interaction warnings is not evident to pharmacists, said Hazel Seaba (left), University of Iowa College of Pharmacy professor (clinical) and director of the Division of Drug Information Service.

"Many systems currently in place give warnings on all possible interactions and potential interactions," Seaba said. "The problem is that some of these may have no clinical significance. Multiple warnings for trivial, potential interactions tend to mask more serious warnings."

The new methodology for evaluating interactions, currently being tested by Seaba and colleagues, was developed by the USP's Therapeutic Decision Making Expert Committee, chaired by Elizabeth Chrischilles (left), Ph.D., professor of epidemiology in the UI College of Public Health.

The new methodology is being tested in two stages. First are the database and reports being developed by Seaba and colleagues, which will compile relevant literature and summarize the level of evidence for a drug interaction. When this is completed, the Expert Committee will review the work and make recommendations about which drug interactions should be included in pharmacy computer databases. That decision will be based on not only the level of evidence but also the seriousness of the potential clinical outcome as well as available therapeutic alternatives, Chrischilles noted.

The new methodology strives to classify drug-drug interactions that pose the greatest risk. Currently, the methodology is being tested on five specific interactions. A hierarchy of evidence on which to evaluate these drugs is being established.

Seaba and her team are researching all published evidence on these interactions to evaluate their validity and relevance.

Once the strength and reliability of such evidence is determined, a new database of interactions could be put into place in community pharmacies, providing up-to-date and accurate information on drug-drug interactions.

A new database would provide pharmacists with better information on which to base their advice for patients. A project like this one will need continual updating, Seaba said, because new drugs are continuously being developed and prescribed.

"With each new drug comes a new possible interaction," she said.

Whether this work results in few irrelevant warnings from pharmacists' computer systems is, to some extent, a matter of expectations, Chrischilles said.

"While drug information and database vendors need to do a better job of being sure that the drug-drug interactions they review are 'important,' pharmacists should realize that, fortunately, most of the time a computer-generated warning does not mean there is a definite problem," Chrischilles said. "Rather, these warnings are intended to prevent problems that can happen in a minority of patients. Clinical judgment will be needed to evaluate whether the risk of a bad outcome is warranted by the benefits likely to be obtained in an individual patient's case."

The DDII is being led by USP, the Academy of Managed Care Pharmacy, the American Pharmacists Association, the American Society for Automation in Pharmacy, the National Association of Chair Drug Stores, the National Community Pharmacists Association and the Pharmaceutical Care Management Association.

University of Iowa Health Science Relations, 5135 Westlawn, Iowa City, Iowa 52242-1178

David Pedersen, [email protected]