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T
he right dose for the right patient: That’s the goal of all pharmacists and physicians. And now, the University of Illinois Hospital & Health Sciences System is pioneering the use of genetics to make that personalized-health aim a reality.
Cavallari, along with Edith Nutescu, PharmD, the founder of the University of Illinois Hospital & Health System’s Antithrombosis Clinic, are the clinical directors behind the health system’s new Warfarin Pharmacogenetics Service, which launched in mid-August.
In its work with new patients taking warfarin (a drug used to treat blood clots and prevent strokes), UI Health is the first in the nation to automatically use pharmacogenetics — the science that predicts a response to drugs based upon a person’s genetic makeup — to prescribe the correct dosage. The project is a collaboration between the University of Illinois at Chicago colleges of Pharmacy and Medicine.
When patients are first prescribed warfarin under the new service, the computer system automatically triggers a laboratory order for warfarin pharmacogenetics and a pharmacy consultation. A small sample of the patient’s blood is drawn and sent to the medical laboratory, where the DNA is isolated and processed on an FDA-cleared genotyping platform. Results for the VKORC1 and eight variations of the CYP2C9 genes are usually available within a mere six to eight hours.
Each year, more than 2 million people are prescribed warfarin, the most widely prescribed oral anticoagulant drug in North America. But determining the right dose, especially the initial critical doses, can be difficult because of variable factors including a patient’s diet, age and the use of other medications. Warfarin is the leading cause of adverse drug reactions among older people in the United States. Patients who take a dose larger than they can tolerate are at risk of life-threatening bleeding. Those who receive too low a dose are at risk of equally dangerous blood clots. The process of personalizing optimal warfarin dosages is based upon data from numerous studies which show that a patient’s variants of the genes CYP2C9 and VKORC1 affect why people process the drug differently. “These two genes explain about 30 percent of the variability in dose that we see in patients,” says Larisa Cavallari, PharmD, an associate professor. “Without using genotype information, it can take weeks or months to figure out the correct warfarin dosage.”
The Pharmacogenetics Consult Service provides a patient assessment and a genotype-guided warfarin dose recommendation to the medical team via a consult note in the patient’s electronic medical record. Patients are then monitored with blood tests to ensure that the dosage is correct. The pharmacogenetics service follows up until the patient is discharged from the hospital, and even after for those receiving care at the university’s Antithrombosis Clinic. Rather than starting all patients on the same initial dose, genotyping personalizes the warfarin dosage for each patient, helping to prevent both overdoses and underdoses of warfarin. Studies have shown that patients who used genotypeguided warfarin dosing had significantly fewer serious adverse events (including hemorrhage, thrombosis and death) during the initial three months of therapy compared with control groups. “Not basing a person’s treatment on one standard is better for the patient,” says Vanessa Flores, a UI Health employee and a patient with a blood clotting disorder, who has been treated for deep Catalyst – Fall 2013 – pharmalumni.uic.edu |
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