From the Journals

Kidney function may help docs pick antiplatelet mix after stroke



Renal function should be considered when determining whether to pick ticagrelor-aspirin or clopidogrel-aspirin as the antiplatelet therapy for patients with minor stroke, according to new research.

The study, which was conducted in 202 centers in China and published in Annals of Internal Medicine, indicates that when patients had normal kidney function, ticagrelor-aspirin, compared with clopidogrel-aspirin, substantially reduced the risk for recurrent stroke within 90 days of follow-up.

However, this effect was not seen in patients with mildly, moderately or severely decreased kidney function.

Rates of severe or moderate bleeding did not differ substantially between the two treatments.

Results gleaned from CHANCE-2 data

The researchers, led by Anxin Wang, PhD, from Capital Medical University in Beijing, conducted a post hoc analysis of the CHANCE-2 (Clopidogrel in High-Risk Patients with Acute Nondisabling Cerebrovascular Events-II) trial.

The trial included 6,378 patients who carried cytochrome P450 2C19 (CYP2C19) loss-of-function (LOF) alleles who had experienced a minor stroke or transient ischemic attack.

Patients received either ticagrelor-aspirin or clopidogrel-aspirin, and their renal function was measured by estimated glomerular filtration rate. The authors listed as a limitation that no data were available on the presence of albuminuria or proteinuria.

The researchers investigated what effect renal function had on the efficacy and safety of the therapies.

Differences in the therapies

Clopidogrel-aspirin is often recommended for preventing stroke. It can reduce thrombotic risk in patients with impaired kidney function, the authors noted. Ticagrelor can provide greater, faster, and more consistent P2Y12 inhibition than clopidogrel, and evidence shows it is effective in preventing stroke recurrence, particularly in people carrying CYP2C19 LOF alleles.

When people have reduced kidney function, clopidogrel may be harder to clear than ticagrelor and there may be increased plasma concentrations, so function is important to consider when choosing an antiplatelet therapy, the authors wrote.

Choice may come down to cost

Geoffrey Barnes, MD, MSc, associate professor of vascular and cardiovascular medicine at University of Michigan Medicine in Ann Arbor, said in an interview that there has been momentum toward ticagrelor as a more potent choice than clopidogrel not just in populations with minor stroke but for people with MI and coronary stents.

He said he found the results surprising and was intrigued that this paper suggests looking more skeptically at ticagrelor when kidney function is impaired.

Still, the choice may also come down to what the patient can afford at the pharmacy, he said.

“The reality is many patients still get clopidogrel either because that’s what their physicians have been prescribing for well over a decade or because of cost issues, and clopidogrel, for many patients, can be less expensive,” Dr. Barnes noted.

He said he would like to see more study in different populations as the prevalence of people carrying CYP2C19 allele differs by race and results might be different in a non-Asian population. That allele is thought to affect how clopidogrel is metabolized.

Study should spur more research

Nada El Husseini, MD, associate professor of neurology and Duke Telestroke Medical Director at Duke University Medical Center, Durham, N.C., said the study is hypothesis generating, but shouldn’t be thought of as the last word on the subject.

She pointed out some additional limitations of the study, including that it was a post hoc analysis. She explained that the question researchers asked in this study – about effect of kidney function on the safety and efficacy of the therapies – was not the focus of the original CHANCE-2 study, and, as such, the post hoc study may have been underpowered to answer the renal function question.

The authors acknowledged that limitation, noting that “the proportion of patients with severely decreased renal function was low.”

Among 6,378 patients, 4,050 (63.5%) had normal kidney function, 2,010 (31.5%) had mildly decreased function, and 318 (5.0%) had moderately to severely decreased function.

The study was funded by the Ministry of Science and Technology of the People’s Republic of China, the Beijing Municipal Science and Technology Commission, the Chinese Stroke Association, the National Science and Technology Major Project and the Beijing Municipal Administration of Hospitals Incubating Program). Salubris Pharmaceuticals contributed ticagrelor and, clopidogrel at no cost and with no restrictions. Dr. Wang reported no relevant financial relationships. Dr. Barnes and Dr. El Husseini reported no relevant financial relationships.

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