NEWARK, N.J., May 21 (UPI) -- A class of painkillers known as COX-2 inhibitors or "superaspirin" -- which include the popular brands Vioxx and Celebrex -- may impair bone healing after a fracture, a new study warned Tuesday.
The drugs are commonly prescribed to reduce pain in patients following broken bone surgery or other procedures that require bone growth to heal, such as hip replacements and certain dental procedures.
"People probably shouldn't take these drugs if they have a bone fracture or some other bone-healing phenomena going on," J. Patrick O'Connor, author of the study, told United Press International.
O'Connor, assistant professor in the departments of orthopedics and microbiology and molecular genetics at the University of Medicine and Dentistry of New Jersey, said he gave Vioxx or Celebrex to rats and monitored bone healing.
"Both drugs significantly negatively affected fracture healing," he said.
The drugs, commonly prescribed to treat arthritis pain and other so-called muscoskeletal injuries -- which involve muscles, bones and joints -- inhibit an enzyme called cylooxygenase-2 or COX-2, which seems to play a role in bone healing.
In an additional experiment, the gene controlling COX-2 was de-activated in mice. As a result, "fracture healing was dramatically impaired," O'Connor said.
"If you stop COX-2 activity, you're going to stop fracture healing," O'Connor said.
Thomas Einhorn, chair of the department of orthopedic surgery at the Boston University School of Medicine, who wrote an editorial accompanying the study, told UPI, "This is the tip of the iceberg."
Einhorn said, "This is the first in about a dozen other articles soon to come out that show very much the same thing," noting his own lab has two studies in progress that also show that COX-2 inhibitors interfere with bone healing.
He pointed out, however, "millions of people have taken (these drugs)... and in orthopedic surgery, we haven't seen a lot of problems with healing," so it may be premature to directly connect the study's findings, obtained from animals, to humans.
Still, it would be unethical to conduct studies in humans to determine if the findings hold true, Einhorn said. So, "the safe thing to do is to err on the side of caution, which would be not to use these drugs during fracture healing, but there's no reason not to go back to them after the fracture is healed."
He added his interpretation of the data is the drugs only delay the healing process. They do not stop it completely. "I wouldn't necessarily worry that these drugs are going to prevent fractures from healing," he said.
O'Connor believes COX-2 inhibitors completely shut down the healing process. He noted physicians at his University have stopped prescribing the drugs for their bone-fracture patients based on his study.
Alternative painkillers that do not impair bone healing include Tylenol and codeine, Einhorn said.
Both Merck, of Whitehouse Station, N.J., the manufacturer of Vioxx, and Pharmacia, of Peapack, N.J., the manufacturer of Celebrex, downplayed the findings of the study.
"It's an animal study ... and it's hard to correlate those results with clinical results you'd see in humans," Pharmacia spokeswoman Stephanie Fagan told UPI. She said there are no studies in humans to date to indicate "that (COX-2 inhibitors) impair bone healing."
Pharmacia has another COX-2 inhibitor on the market called Bextra, and it is currently conducting a study to determine if the drug interferes with bone healing, Einhorn added.
Merck spokesperson Chris Fanelle maintained "there's nothing in our labeling to suggest that there would be any concern" over giving Vioxx to a patient with a bone fracture.
The study appears in the June issue of the Journal of Bone and Mineral Research.
(Reported by UPI Medical and Health Correspondent Steve Mitchell in Washington)