UNC Health Care

Some popular non-aspirin pain drugs may slow tendon healing, new study finds

Some popular anti-inflammatory drugs slow tendon healing in laboratory animals when taken immediately after surgery, according to research conducted at the University of North Carolina at Chapel Hill.

“Pain control is one of the biggest issues sports medicine physicians confront after an injury or after surgery,” said Dr. Scott T. Ferry, a resident physician at UNC Hospitals. “There is a lot of interest in not using large doses of narcotics, so we often use Tylenol or some of the other anti-inflammatory medications to help control pain. Consequently, it is important to know if any of these medications delay or prevent healing.”

Ferry is presenting an abstract on the UNC research during the American Orthopaedic Society for Sports Medicine’s Specialty Day session at the American Academy of Orthopaedic Surgeons’ annual meeting on Saturday (March 25) in Chicago. He is the abstract’s lead author.

“Rats treated immediately following surgical repair with COX-2 inhibitors, including Celecoxib (Celebrex) and Valdecoxib (Bextra), had weaker tendons, and a higher percentage of tendons did not heal compared to the control group,” Ferry said.

COX-2 inhibitors block an enzyme called cyclooxygenase-2 (COX-2) that is associated with pain and inflammation. They are the latest nonsteroidal anti-inflammatory drugs, or NSAIDs. COX-2 inhibitors are generally regarded as having the same effectiveness against pain and swelling of inflammation as the older NSAIDs but without the increased risk of gastrointestinal side effects, including stomach ulcers, which have been linked to NSAID use.

“We also studied several commonly used nonselective COX inhibitors, which inhibit both the COX-1 and COX-2 enzymes. With these type of NSAIDs, such as naproxen (Aleve) and piroxicam (Feldene), the tendons were slightly weaker, but not nearly as marked as with the COX-2 inhibitor-treated group,” Ferry said.

Previous studies have demonstrated that some pain relievers are detrimental to bone healing when given immediately after injury or surgery. In addition, research led by Dr. Laurence E. Dahners, a professor in the UNC School of Medicine’s department of orthopaedics, found that COX-2 inhibitors slowed ligament healing. Ferry and his colleagues, which included Dahners as second author, tested the same principle for tendon healing to the bone.

The other authors are Hessam M. Afshari, a research assistant; and Dr. Paul S. Weinhold, an associate professor in the departments of orthopaedics and biomedical engineering and principal investigator of the project.

Ferry and colleagues evaluated patellar tendon strength and healing following tendon rupture and repair in 164 rats to determine the effect of commonly prescribed analgesics on the tendon healing.  The patellar tendon connects the kneecap (patella) to the shinbone (tibia).  After surgery, the rats were divided into six treatment groups receiving celecoxib, naproxen, piroxicam, acetaminophen, ibuprofen or valdecoxib in their rat chow. The seventh group received no medication and served as the control.

The researchers found that COX-2 inhibitors appeared to interfere with patellar tendon healing. This was demonstrated by the following incidence of tendon repair suture failures: control (0 failures out of 23 specimens), acetaminophen (0/24), celecoxib (6/22), ibuprofen (0/23), naproxen (3/24), piroxicam (4/24) and valdecoxib (10/24).

The decreased maximum load and ultimate stress in the specimens that did not fail also pointed to slow healing. To a lesser degree, similar changes were seen with the nonselective COX inhibitors piroxicam and naproxen. Ibuprofen and acetaminophen did not appear to inhibit healing strength.

The researchers concluded that both selective and nonselective COX inhibitors should be used judiciously in the early period for injuries where tendons attach to bones. Ferry said he is avoiding prescribing the COX inhibitors immediately following surgery. “Narcotic medications definitely play a role after injury and after surgery,” he said.

Funding for the study was provided by McNeil Consumer & Specialty Pharmaceuticals, which manufactures several popular nonprescription pain medicines, including Tylenol, Imodium and Motrin.