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In-Hospital Switching of Antiplatelet Agents in MI Patients Relatively Common, Driven by Patient Risk, Other Factors

By L.A. McKeown

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Patients who undergo percutaneous coronary intervention (PCI) for acute myocardial infarction (MI) are frequently switched from one ADP receptor inhibitor to another prior to hospital discharge, with factors such as repeat PCI, risk for recurrent thrombotic events, and insurance coverage all influencing the decision, according to a study published online August 5, 2014, in Circulation: Cardiovascular Interventions.  

Methods
Akshay Bagai, MD, MHS, of St. Michael’s Hospital (Toronto, Canada), and colleagues looked at 47,040 MI patients who underwent PCI and received either clopidogrel or prasugrel within 24 hours of admission and at hospital discharge at 361 US hospitals from July 2009 to June 2011. The data, obtained by linking the ACTION Registry–Get With the Guidelines and CathPCI Registry, were used to track temporal trends in switching medications and the factors affecting the decision. 


Overall, 86.1% of patients were treated initially with clopidogrel, while 13.9% initially received prasugrel. Of those started on clopidogrel, 5.2% were switched to and discharged on prasugrel, while 11.5% treated initially with prasugrel were switched to and discharged on clopidogrel.   

To Switch or Not to Switch  

Over the course of the study, the rate of switching from clopidogrel to prasugrel increased from 0 to 7%. The rate of switching from prasugrel to clopidogrel increased initially from 6% to 18%, decreased abruptly in the second quarter of 2010, and then declined gradually to 9% by the end of the study period.

Except at the start of the study, temporal trends in the frequency of switching from clopidogrel to prasugrel were similar for patients presenting with STEMI and NSTE-ACS.    

The rate of switching varied widely across hospitals for both the switch from clopidogrel to prasugrel (range, 0 to 42.9%) and from prasugrel to clopidogrel (range, 0 to 86%).   

Among patients treated initially with clopidogrel, a switch to and discharge on prasugrel was most strongly associated with:

  • In-hospital reinfarction (OR 2.99; 95% CI 2.18-4.12) 
  • Number of PCI procedures (OR 2.41; 95% CI 2.09-2.78)   

These patients also had high angiographic risk characteristics, including intracoronary thrombus, longer lesion length, bifurcating culprit lesion, and multivessel PCI, and more frequent clinical risk characteristics, such as prior PCI and diabetes. Having private health insurance coverage to cover the cost of the newer drug vs no insurance also was associated with a switch to prasugrel (OR 1.20; 95% CI 1.05-1.36), while Medicare or Medicaid coverage was associated with continuation on clopidogrel. Patients at increased bleeding risk—due to older age, previous stroke or TIA, A-fib/flutter, and in-hospital CABG—also were more likely to continue on clopidogrel.    

Among patients treated initially with prasugrel, a switch to and discharge on clopidogrel was most strongly associated with in-hospital bleeding and factors associated with increased bleeding risk.    

On the other hand, continuation and discharge on prasugrel was most strongly tied to health insurance coverage—both private and Medicare or Medicaid. Other factors included:

  • STEMI presentation 
  • Treatment with DES  
  • Preadmission treatment with prasugrel  
  • Increased body weight   

Of those with previous stroke or TIA who were initially treated with prasugrel, 67.2% were continued and discharged on that drug.   

More Education on Bleeding Risk Needed   

“It is reassuring that consistent with the available literature and practice guidelines, for the most

part,… patients with previous stroke or TIA [who were initially given prasugrel] are switched to and discharged on clopidogrel,” the study authors write. However, further educational efforts are needed in this regard, they say, noting that the use of risk prediction models “may allow better selection and tailoring of ADP receptor therapy based on an individual patient’s risk profile.”   

Dr. Bagai and colleagues observe that the overall rate of switching from prasugrel to clopidogrel in the study was high shortly after US Food and Drug Administration approval of the new antiplatelet agent in 2009, “likely because of lack of familiarity with the new drug and concern about availability in outpatient pharmacies.”

An important study limitation, the authors acknowledge, is lack of information from the treating clinicians on the reason for switching agents, as well as information about patient or physician preference, allergies, the use of platelet reactivity testing, loading dose at the time of the switch, timing of switching relative to cardiac catheterization/PCI, and clinical outcomes associated with switching.  

Finally, they observe, switching rates may have increased since the end of the study in June 2011, given the wider availability of novel ADP receptor inhibitors. 

  

Source: 
Bagai A, Wang Y, Wang TY, et al. In-hospital switching between clopidogrel and prasugrel among patients with acute myocardial infarction treated with percutaneous coronary intervention: insights into contemporary practice from the National Cardiovascular Data Registry. Circ Cardiovasc Interv. 2014;Epub ahead of print. 

Disclosures:

  • Dr. Bagai reports no relevant conflicts of interest. 

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