Gene Test Promises to Find Right Drug, Right Dose The wrong prescription and dose can mean ineffective drugs and harmful side effects. A new test, part of the growing science of pharmacogenetics, is designed to help doctors figure out which drugs and doses are right for their patients.
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Gene Test Promises to Find Right Drug, Right Dose

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Gene Test Promises to Find Right Drug, Right Dose

Gene Test Promises to Find Right Drug, Right Dose

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JOHN YDSTIE, host:

This is MORNING EDITION from NPR News. I'm John Ydstie.

RENEE MONTAGNE, host:

And I'm Renee Montagne.

In Your Health today, we begin with genetics. The Mayo Clinic has announced that it's selling a new test that will help doctors figure out who will benefit from certain drugs. NPR's Joanne Silberner reports that pharmacogenetic testing is already helping many people.

JOANNE SILBERNER reporting:

Finding the right drug and the right dose for almost any disease is part of the art of medicine. But a few years ago that art wasn't working for Marla Flood's son Jacob. Jacob has autism and, his mother says, a long history of biting, hitting, kicking and scratching.

Ms. MARLA FLOOD (Parent): We have probably tried every drug there is for the treatment of his aggressiveness, his obsessive type behaviors. He's always had a negative reaction to them, either an increase in his aggression or just some side effects that were very harmful to him.

SILBERNER: His doctor at Cincinnati Children's Hospital, autism expert, Patty Manning-Courtney, says she'd seen it before.

Dr. PATTY MANNING-COURTNEY (Autism Specialist, Cincinnati Children's Hospital): Occasionally, there were patients who didn't respond, who got worse on medication, and that's actually not that uncommon of a scenario in children with autism, and it's a lot of trial and error practice with medicines.

SILBERNER: Jacob Flood was put on Risperdal, a powerful antipsychotic that helps many children with autism and behavior problems. But it hurt Jacob, says his mother.

Ms. FLOOD: Jake started having tremors. He would just shake all over, unable to focus. I would give him his medications. He would sit down on my lap and just be a zombie. That's the only way I can really describe what he looked like.

SILBERNER: Jacob's hospital is a pioneer in the new field of pharmacogenetic testing. It offers tests for two genes that control how the body metabolizes 25 percent of all drugs, including some used for autism. The genes produce enzymes that break down the drugs. And sure enough, when Dr. Patty Manning ordered the tests on Jacob…

Dr. COURTNEY-MANNING: We got the testing obtained and the results came back that he was an intermediate metabolizer for one enzyme system and a slow metabolizer for another, placing him in that small but significant minority of patients who metabolize differently.

SILBERNER: In other words, a normal dose of Risperdal was actually an overdose for Jacob. So Marla Flood agreed to start her son back on the drug at an extra low dose.

Ms. FLOOD: Now he is not near as aggressive as he has been. I don't have bruises on me now.

SILBERNER: The promise of pharmacogenetic testing is that people will get the right dose of the right drug. Sometimes the test show a drug doesn't work. For example, when it comes to Codeine, 7 percent of whites and 2 percent of blacks can't metabolize it. All people get are the side effects and none of the pain relief.

There are commercial pharmacogenetic tests available. Only one is approved by the Food and Drug Administration. Tests cost about $300 to $600, and are often covered by insurance. Some university hospitals do their own testing, and the Mayo Clinic offers some tests nationally. Pharmacogenetics pioneer David Flockhart of Indiana University says the question is who should be tested and when.

Mr. DAVID FLOCKHART (Pharmacogenetics Pioneer, Indiana University): Well, you can argue that everybody should at birth, and we may eventually end up there.

SILBERNER: Flockhart says it will take more research before doctors embrace tests. So what if you're currently taking a drug that doesn't seem to be doing anything, or worse, it's only creating bad side effects. Flockhart says, talk to your doctor.

Mr. FLOCKHART: We're getting better at this, and patients are their own best advocates. So I think it's very reasonable for people to say, is there any way to predict whether or not I'm getting the side effects from this drug or whether or not it will work, because I know there are tests coming along.

SILBERNER: Other experts, including Russ Altman of Stanford University, say pharmacogenetics is such a new science that most doctors didn't learn about it in medical school. And he says clinicians have to find a laboratory that offers the tests and learn how to read the results.

The FDA already recommends doctors consider a gene test before prescribing certain drugs for breast and colon cancers, as well as the attention deficit hyperactivity drug, Strattera.

Joanne Silberner, NPR News.

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