Many people reach for a painkiller when they have a headache or when their arthritis is acting up, but what if you're already taking aspirin every day? For people taking daily aspirin therapy to reduce their risk of heart attack and stroke, a recent study shows that regular use of other common painkillers might interfere with the benefits of the aspirin.
Aspirin, considered the wonder drug of the century, has been used for more than a hundred years taken to reduce pain. It belongs to a class of drugs known as non-steroidal anti-inflammatory drugs, or NSAIDs. In recent years, aspirin was found to impair platelets, the cells that are involved in clotting blood. This action helps minimize risk for heart attack and stroke by preventing blood vessels from being blocked when the cells clump together, cutting off the blood supply to the heart or brain.
While aspirin is capable of blocking an important enzyme and disabling platelets for good, other NSAIDs can only block the enzyme temporarily.
In the study, which was published in the September 9 issue of the journal Circulation, researchers used data from the Physician's Health Study, a randomized trial of more than 22,000 men that found daily aspirin led to a 44 percent reduction in first heart attack. Researchers examined those participants who used non-aspirin NSAIDs occasionally, defined as less than 60 days a year, and those who used them regularly. They found that men who used non-aspirin NSAIDs regularly did not experience a reduction in heart attacks. (The study did not look at COX-2 inhibitors, a newer class of anti-inflammatory drugs.)
Below, lead author Tobias Kurth, MD, ScD, an instructor of medicine at Harvard Medical School and a researcher in the division of preventive medicine at the Brigham and Women's Hospital in Boston, discusses the study findings and potential options for people on aspirin therapy who need painkillers for other problems.
When is daily aspirin therapy usually recommended?
Daily aspirin therapy is used in both primary and secondary prevention. If you never had a cardiovascular event, but have some risk factors, then daily aspirin therapy to reduce risk of first heart attack is called primary prevention. Secondary prevention is if you are taking daily aspirin therapy after having had a cardiovascular event, such as a heart attack.
It has been known for many years that aspirin is effective in preventing a second event. For primary prevention, if you have a number of risk factors, then daily aspirin is currently recommended to prevent first heart attack.
The American Heart Association recommends 75 mg to 165 mg of aspirin daily for primary prevention, and a daily dose of 75 mg to 325 mg daily for secondary prevention.
Who is a good candidate for daily aspirin therapy?
Someone who is at high risk for cardiovascular disease is generally a good candidate. Risk factors for heart attack include high blood pressure, cholesterol and family history of heart attack or diabetes.
Of course, people who do not tolerate aspirin, who have allergic reactions or have had bleeding events such as gastrointestinal bleeding, should not take aspirin. Bleeding events can occur with aspirin therapy because one of the ways aspirin works is by inhibiting the aggregation of platelets blood cells that assist in clotting.
How does aspirin reduce risk?
Aspirin interacts with an enzyme called cyclooxygenase-1, the so-called COX-1 enzyme. By doing so, it irreversibly inhibits the aggregation of platelets. An aggregation of the platelets can cause clotting in the arteries, which can lead to a heart attack or an ischemic stroke. So if you take aspirin and this aggregation is inhibited, you're less likely to have such events.
How do the other NSAIDs work?
There are several different so-called NSAIDs, including aspirin and ibuprofen. These drugs are also working on the COX enzyme. In the COX family, there are several forms of this enzyme and, with aspirin and other NSAIDs, COX-1 and 2 play a role. COX-2 is involved in the pain pathway. There is a newer generation of NSAIDs that only interact with COX-2, and not with COX-1. Virtually none of our participants took COX-2 inhibitors, however, because the study took place before these drugs were on the market. [Since the publication of this article, the COX-2 inhibitor Vioxx has been taken off of the market because of links to increased heart attack and stroke risk, and the safety of other COX-2 inhibitors has been called into question.]
Why do some NSAIDs inhibit aspirin?
Both aspirin and other non-aspirin NSAIDs can work on the COX-1 enzyme. But, the enzyme can probably be blocked only by either aspirin OR another NSAID. Unlike aspirin, however, other NSAIDs impair platelet function for just a limited time, and the platelets regain function after these NSAIDs leave the body. Thus, if both medications are taken together, other NSAIDs may interfere with aspirin's effect on COX-1.
What did your study find?
First, the overall study found that aspirin was highly effective to prevent first heart attack, with a 44 percent risk reduction. The most stable result of our study is that occasional users of NSAID, which are probably most users of NSAIDs, are not affected by an interaction of aspirin and other NSAIDs. Our studies suggest that those who take other NSAIDs regularly do not have the beneficial effect of aspirin, which does not mean that there is an increased risk of heart attack compared to taking nothing, but just that aspirin is not as efficient if you take the other NSAIDs regularly.
What are the options for people who take daily aspirin and have chronic pain?
That is very difficult to answer at this point. But one study suggested that if you take your aspirin somewhat before your NSAID, the interaction might not occur. When you take your aspirin before, the aspirin has time to work on the COX-1 enzyme. Then when you take your other NSAID, it won't interact with aspirin because the COX-1 is already being blocked by aspirin.
So if you take the aspirin and then somewhat later, let's say around two hours or so take the NSAID for pain, you might avoid the problem. We need more information, but to the best of my knowledge, that might be a solution.
Is it known if certain NSAIDs inhibit aspirin less than or more than others?
In our study, we had no information about specific NSAIDs. In the first two studies that came out, this effect was only shown for ibuprofen, but not for other NSAIDs.
Should someone experiencing pain stop taking aspirin therapy temporarily?
No, that's not a good idea. Even if, in theory, that effect might be gone if you're taking an NSAID, you still want to continue to take the aspirin.
If you have to take aspirin and another NSAID regularly, I think the best recommendation is to talk to the treating physician about this issue. See if you should take your aspirin prior to the NSAID.
©2007 Healthology, Inc.