At-Home Test Could Help Protect Against Drug Side Effects

Genetics Make Some People More Vulnerable to Adverse Reactions

By Jim Morelli, RPh
WebMD Medical News

Reviewed by Dr. Michael W. Smith

Sept. 15, 2000 (Atlanta) -- Everyone has a different genetic makeup and thus reacts differently to drugs. That's the basic understanding behind pharmacogenomics -- a field that is one day expected to lead to drugs specifically designed for an individual's genes. That should make drug therapy safer. But until then, consumers will continue to take the same drugs everyone else takes -- and in the process, put themselves at risk for potentially serious side effects.

Now, though, researchers have now come up with a way for people to screen themselves for genetic vulnerability to side effects from certain drugs, using a simple inside-the-cheek swab test. PPGx Inc. of Morrisville, N.C., hopes to bring its version to market this fall. Another system is being tested at Georgetown University Medical Center in Washington. The idea is to pick up genetic danger signs that would indicate, for example, that a drug is likely to be metabolized at a slower-than-desired rate, leading to a toxic accumulation in the blood.

Randall Tackett, PhD, a professor of pharmacology at the University of Georgia in Athens, says the time may have come for such tests. "The thing is, we're using more powerful drugs, combination therapies, and people are on drugs for a longer period of time," he says. "Plus, more drugs are going over-the-counter." All of that spells more potential for drug interactions and side effects.

With the PPGx test, consumers will do the swabbing at home, then send off the sample to a gene-testing laboratory. The test will look for variations in what's known as the P-450 2D6 gene, which can affect the metabolism of about a quarter of prescription drugs now on the market -- including some of the top sellers.

"There is a list of between 30 and 50 drugs for which there is a documented alteration in either the safety or efficacy," depending on whether a person has this genetic vulnerability, says Rick Sheridan, PhD, vice-president for Information Science at PPGx. "It covers a wide variety of drugs, from antidepressants to codeine to the dextromethorphan in Robitussin."

After consumers get a report and analysis from the swab, they'll follow-up -- much as with other home tests -- with a physician, Sheridan says.

"I'm not sure how efficient that will be," Tackett says. "But I think the test would be an important addition for physicians." In fact, if the tests have any impact at all, it would be an important one. One recent analysis puts the number of Americans hospitalized with drug side effects each year at 2 million, with 100,000 of them dying. Larry Sasich of the Public Citizen Health Research Group, which tracks prescription drug problems, says it's likely the number is higher -- given that only hospitalized patients were included in the count.

Sheridan suggests that the aging of the U.S. population could make the side-effect situation even worse. Younger bodies, he argues, can sometimes handle "genetically inappropriate" drugs better than older ones.

Meanwhile, at Georgetown University, researchers are looking down the road toward another type of genetic test -- one that could detect the alteration that makes it more likely for some people to develop potentially fatal irregular heartbeats from certain prescription drugs.

© 2000 WebMD Corporation. All rights reserved.