LOS ANGELES — Approximately 75% of patients receiving dual antiplatelet therapy with a P2Y12 inhibitor are receiving the wrong dose, according to findings in an abstract presented at the American Heart Association Scientific Sessions 2012.
“There’s a sweet spot, an appropriate range for each patient, but we found that not many people are falling into that range,” study researcher Brent Muhlestein, MD, of the Intermountain Medical Center Heart Institute, said in a press release.
Guidelines for the use of platelet-function testing developed by the Intermountain Healthcare department of cardiovascular medicine recommend changing medication dosing or type to reach a target of 100 P2Y12 reaction units (PRUs) to 200 PRUs, as measured by the VerifyNow assay. Muhlestein and colleagues used this platelet-function test to evaluate 521 patients (mean age, 68 years; 66% men) receiving DAPT with clopidogrel (Plavix, Sanofi-Aventis) or prasugrel (Effient, Daiichi Sankyo/Eli Lilly) and determine whether their doses were appropriate for reaching the target PRU range.
Mean PRU levels for those receiving clopidogrel (n=381) were 211.5. Of these patients, 17.3% had PRU levels <100; 25.5% had levels between 100 and 200; and 57.2% had PRU levels of >200, according to the abstract. For patients receiving prasugrel (n=140), mean PRU levels were 107.6. Among these patients, 55.7% had PRU levels <100; 22.9% had PRU levels between 100 and 200; and 21.4% had PRU levels of >200.
These results suggest, according to the abstract, that only about 25% of patients were initially within target range.
“We showed that by performing a simple blood test to see whether or not the blood is clotting properly, we can determine whether patients are getting an appropriate, individualized dose of the medications. The test is easy to perform, but not widely used,” Muhlestein, who presented the data, said.
The researchers also found that baseline variables of age, sex, hypertension, hyperlipidemia, HF, renal failure and prior cardiac history or other nonplatelet-related medications were not predictive of PRU levels.
“That means there’s not an easy way to predict how a person will react to these drugs. But the blood test is very effective,” Muhlestein said.
For more information:
Bair TL. Abstract #17054. Presented at: the American Heart Association Scientific Sessions 2012; Nov. 3-7, 2012; Los Angeles.
Disclosure: The researchers report no relevant financial disclosures.