Aspirin appears to be just as good as more expensive, more potent
blood-thinning medication for preventing blood clots after hip replacement
surgery, according to new research.
People who get artificial hips are at risk of serious blood clots, such as
deep vein thrombosis and pulmonary embolism, after the surgery. To prevent them,
doctors usually prescribe blood-thinning (anticoagulant) medications, such as
low-molecular-weight heparin, which is given by injection, or the newer drug,
rivaroxaban (brand name Xarelto), a pill.
But that old medicine-cabinet standby, aspirin, also has blood-thinning
properties. And the Canadian researchers wondered if this simple, inexpensive
drug could also prevent blood clots after a major surgery.
They compared the drugs for four weeks, following 10 days of treatment with
heparin immediately post-surgery.
The investigators found the two medications were similarly effective and
safe. Where the medicines differ significantly is in cost.
Low-cost and effective
"Low-molecular-weight heparin and the newer blood thinner, Xarelto, are
similarly priced; they're several hundred-fold more expensive than aspirin,"
said the study's lead author, Dr David Anderson, a professor and head of the
department of medicine at Dalhousie University in Halifax, Nova Scotia.
"Given the low cost of aspirin and its convenience, it's a reasonable
alternative to low-molecular-weight heparin when used in the manner designed in
this trial," said Anderson.
Another expert said the study results, published in the
Annals of Internal Medicine, support previous observations. "After
initial treatment with an anticoagulant, then giving aspirin to these patients
for the prevention of [serious blood clots] is as good," said Jawed Fareed,
professor of pharmacology and pathology and director of the homeostasis and
thrombosis research unit at Loyola University Medical Center in Maywood,
For the study, Anderson and his colleagues recruited 778 patients undergoing
elective hip replacement surgery between 2007 and 2010. All received 10 days of
heparin (dalteparin) following surgery. After that, they were randomised into
one of two groups for four more weeks of blood-thinning therapy. Half continued
receiving heparin injections, while the other half took low-dose (81 milligrams)
Five people on dalteparin and one on aspirin developed a blood clot. The
absolute difference between the two therapies was 1%. Bleeding events serious
enough to require treatment occurred in five people on dalteparin, and two on
Anderson said the difference in bleeding events wasn't statistically
significant, but there was a trend toward aspirin being the safer alternative.
However, it's too soon to tell definitively whether aspirin might cause less
bleeding, he said.
Anderson said the researchers had to stop the study early because they
weren't able to recruit the desired number of patients. While the study was
under way, Xarelto was approved, and because it's a pill instead of an
injectable like dalteparin (brand name Fragmin), it became difficult to find
volunteers for the multiple injection part of the trial.
Duplicating the study
The researchers are now duplicating the study, but comparing Xarelto to
aspirin this time. They're also including people having knee replacement
surgery, and they're only using five days of initial treatment with the more
"If aspirin turns out to be as good as Xarelto, given the number of joint
[replacement] surgeries done in North America, it could save the health care
system millions if it's proven to be at least as effective," said Anderson.
Fareed said he would not use aspirin immediately after the surgery. "But once
that initial phase settles down, I think aspirin is a good option. And, I'm
confident that the bleeding will be less with aspirin," said Fareed.
He said doctors may not turn to aspirin right away, and would probably wait
until medical groups write new guidelines suggesting aspirin as the standard of
care. But it's certainly a topic that patients could bring up with their doctor
before surgery, he suggested.
"I think we have demonstrated that a very simple, inexpensive oral therapy
appears to be as good as a more expensive, more potent, less convenient
anticoagulant agent for the prevention of blood clots following total hip
replacement," concluded Anderson.
The US Agency for Healthcare Research and Quality has more on preventing