Navigation Links
'Resistance' to low-dose aspirin therapy extremely rare
Date:12/5/2012

PHILADELPHIA Roughly one-fifth of Americans take low-dose aspirin every day for heart-healthy benefits. But, based on either urine or blood tests of how aspirin blocks the stickiness of platelets blood cells that clump together in the first stages of forming harmful clots up to one third of patients are deemed unlikely to benefit from daily use. Such patients are called "aspirin resistant." Clots are the main cause of most heart attacks and strokes.

In people who have suffered a heart attack, low-dose aspirin reduces the chances of a second event by about one fifth, making it perhaps one of the most cost-effective drugs currently prescribed. Although consumed widely by the worried well, the relative usefulness of low-dose aspirin in patients who have never had a heart attack is more controversial. According to previous primary prevention studies, low-dose aspirin reduces this group's very low risk of a first attack by about the same number of serious stomach bleeds it causes.

In a study of 400 healthy volunteers published online this week in Circulation, the journal of the American Heart Association, scientists from the Perelman School of Medicine at the University of Pennsylvania, went looking for people who are truly resistant to the benefits of aspirin, such as might result from a particular genetic makeup. They failed to find one case of aspirin resistance; rather, they found "pseudoresistance," due to the coating found on most brands of aspirin, often preferred by patients for the protection it is claimed to provide the stomach. What's more, a urine biomarker of platelet stickiness was not able to find which volunteers were even pseudoresistant.

The study was led by Tilo Grosser MD, research assistant professor of Pharmacology, Susanne Fries, MD, research assistant professor of Pharmacology, and Garret FitzGerald, MD, FRS, director of the Institute for Translational Medicine and Therapeutics.

"When we looked for aspirin resistance using the platelet test, it detected it in about one-third of our volunteers," said Grosser. "But, when we looked a second time at the incidence of aspirin resistance in the volunteers, the one-third that we measured who was now resistant was mostly different people. Nobody had a stable pattern of resistance that was specific to coated aspirin."

Presently a blood test using a specific device can be used in the doctor's office to diagnose "aspirin resistance." Alternatively, an FDA-approved urine test is available for an indirect marker of platelet stickiness. Either can be used to determine if a patient is likely to benefit from aspirin. However, neither approach was supported by the Penn study. The blood test picked up pseudoresistance, while the urine test failed even to segregate these individuals from those clearly responsive to aspirin.

To address the reason for this pseudoresistance, the researchers compared test results of coated aspirin with the same dose of regular uncoated aspirin in volunteer subgroups for coated versus immediate-release, uncoated aspirin. Resistance was absent in the group that took the uncoated aspirin.

The coating delayed absorption compared to immediate-release, uncoated aspirin. This led to a false impression of aspirin resistance in people taking coated aspirin. Platelets of such patients remained sensitive to aspirin when examined in a test tube, so they were not truly resistant to the action of aspirin.

Uncoated, immediate-release aspirin is generic and cheap - less than 1 cent per pill but most low-dose aspirin taken in the U.S. is the more expensive, coated, branded variety. Although supposedly easier on the stomach, coating of aspirin has never been shown to reduce the likelihood of serious stomach bleeds compared to the same dose of uncoated aspirin.

"These studies question the value of coated, low-dose aspirin," notes FitzGerald. "This product adds cost to treatment, without any clear benefit. Indeed, it may lead to the false diagnosis of aspirin resistance and the failure to provide patients with an effective therapy. Our results also call into question the value of using office tests to look for such resistance."


'/>"/>

Contact: Karen Kreeger
karen.kreeger@uphs.upenn.edu
215-349-5658
University of Pennsylvania School of Medicine
Source:Eurekalert  

Related medicine news :

1. New drug overcomes resistance in patients with rare sarcoma
2. Drug resistance biomarker could improve cancer treatment
3. Many Americans Still in the Dark About Antibiotic Resistance
4. Understanding antibiotic resistance using crystallography and computation
5. Recent findings may help to fight melanomas resistance to chemotherapy
6. Scripps Research Institute receives $20 million to shed light on HIV drug resistance
7. UCI researchers find cause of chemotherapy resistance in melanoma
8. Mutation breaks HIVs resistance to drugs
9. Protein linked to therapy resistance in breast cancer
10. New Strep Throat Guidelines Tackle Antibiotic Resistance
11. Environmental Gene-Swapping May Play Part in Antibiotic Resistance
Post Your Comments:
*Name:
*Comment:
*Email:
Related Image:
'Resistance' to low-dose aspirin therapy extremely rare
(Date:10/13/2017)... ... October 13, 2017 , ... ... process to promote standards of excellence for the field of eating disorders, announces ... 22 – 25, 2018 in Orlando, Florida at the Omni Resort at ChampionsGate. ...
(Date:10/13/2017)... ... October 13, 2017 , ... Lori R. Somekh, founder of the ... a national organization of elder law and special needs planning attorneys. “Membership in ElderCounsel ... also provides a forum to network with elder law attorneys nationwide,” said Somekh. ...
(Date:10/13/2017)... ... 2017 , ... The Visiting Nurse Association (VNA) of Somerset Hills is proud ... and unique items from across the nation, this holiday-themed event will raise funds and ... the VNA. The boutique will be open Saturday, November 4 (10:00 a.m. – ...
(Date:10/13/2017)... ... October 13, 2017 , ... Yisrayl Hawkins, Pastor and Overseer at ... of the most popular and least understood books in the Holy Scriptures, Revelation. The ... that have baffled scholars for centuries. Many have tossed it off as mere rubbish, ...
(Date:10/13/2017)... ... ... “The Journey: From the Mountains to the Mission Field”: the story of a ... “The Journey: From the Mountains to the Mission Field” is the creation of published ... all ages and currently teaches a class of ladies at her church, which she ...
Breaking Medicine News(10 mins):
(Date:10/5/2017)... 5, 2017  In response to the nationwide ... Maxillofacial Surgeons (AAOMS) released prescribing recommendations that urge ... used as a first-line therapy to manage a ... Recognizing the value and importance ... "Opioid Prescribing: Acute and Postoperative Pain Management" stresses ...
(Date:10/2/2017)... , Oct. 2, 2017  Eli Lilly and Company ... results for the third quarter of 2017 on Tuesday, ... call on that day with the investment community and ... The conference call will begin at 9 a.m. ... access a live webcast of the conference call through ...
(Date:9/28/2017)... Cohen Veterans Bioscience and Early Signal Foundation announce a ... sensors for real-time monitoring of patients with trauma-related and ... focused on disruptive health solutions for rare disorders and ... record and integrate behavioral, cognitive, physiological and contextual data. ... ...
Breaking Medicine Technology: