A recent study from the University of Bern in Switzerland finds that acetaminophen, taken alone, is an ineffective treatment for osteoarthritis, no matter the dose. In fact, the researchers found it to be only marginally better than a placebo.
Matt Lambie, Pharm.D., the Pharmacy Clinical Manager at Indian River Medical Center, is not surprised by these results. He says, “There was a meta-analysis published in 2014 that also showed acetaminophen was ineffective for knee, hip and lower back pain, the primary cause of which is osteoarthritis.” (In laymen’s terms, a meta-analysis uses a statistical approach to combine results from multiple studies to develop a more accurate conclusion.)
Acetaminophen is the active ingredient in hundreds of over-the-counter medicines (the best known of which is Tylenol) that are commonly touted as first-line treatments for osteoarthritis.
The Swiss researchers set out to determine which medications are most effective for treating osteoarthritis pain. They analyzed the data of 74 studies conducted over a 35-year period; the studies included nearly 59,000 patients with osteoarthritis, and compared the effects of 22 different medications at various doses.
The study, published in the UK medical journal The Lancet, showed that while some doses of acetaminophen provided patients with a slight improvement, the effect did not reach what is called the “minimum standards of clinical effectiveness,” defined as the smallest change in a treatment outcome that a patient would deem important. In other words, acetaminophen really didn’t help patients with osteoarthritis.
According to the research, what did help those patients was diclofenac, a non-steroidal anti-inflammatory drug (NSAID), at a daily dose of 150 mg; its common brand names – available by prescription and over-the-counter – are Voltaren, Cataflam and Zipsor. Diclofenac’s effectiveness was found to be greater than the maximum doses of other NSAIDs frequently used for the treatment of osteoarthritis, including ibuprofen (Motrin, Advil) celecoxib (Celebrex) and naproxen (Aleve).
IRMC’s Lambie says that diclofenac’s effectiveness is driven by its pharmacology – it blocks the effect of cyclo-oxygenase (COX) enzymes, which in turn reduces the production of other pain-causing chemicals called prostaglandins. “Other NSAIDs target just one type of COX enzyme,” Lambie says. “Diclofenac targets both types, and it tends to be more potent.”
Study leader Dr. Sven Trelle says, “NSAIDs are usually only used to treat short-term episodes of pain in osteoarthritis, because the side effects are thought to outweigh the benefits when used longer-term. Because of this, acetaminophen is often prescribed to manage long-term pain instead of NSAIDs. However, our results suggest that acetaminophen at any dose is not effective in managing pain in osteoarthritis.”
Osteoarthritis is the most common form of arthritis, affecting an estimated 27 million Americans, primarily those over the age of 65. In the condition, there is a breakdown of joint cartilage (the connective tissue that covers the end of the bones, acting as a cushion), which causes the bones to rub together, resulting in inflammation, stiffness and pain. Although osteoarthritis can affect any joint in the body, the hands, knees, hips and spine are most commonly affected.
The Mayo Clinic lists the following factors that increase the risk of developing osteoarthritis:
• Older age. The risk of osteoarthritis increases with age.
• Sex. Women are more likely to develop osteoarthritis, although it isn’t clear why.
• Obesity. Carrying extra body weight contributes to osteoarthritis in several ways, and the more you weigh, the greater your risk. Increased weight puts added stress on weight-bearing joints, such as your hips and knees. In addition, fat tissue produces proteins that may cause harmful inflammation in and around your joints.
• Joint injuries. Injuries, such as those that occur when playing sports or from an accident, may increase the risk of osteoarthritis. Even injuries that occurred many years ago and have seemingly healed can increase your risk of osteoarthritis.
• Certain occupations. If your job includes tasks that place repetitive stress on a particular joint, that joint may eventually develop osteoarthritis.
• Genetics. Some people inherit a tendency to develop osteoarthritis.
• Bone deformities. Some people are born with malformed joints or defective cartilage, which can increase the risk of osteoarthritis.
Although people with osteoarthritis should avoid high-impact exercise, some forms of exercise can be beneficial, including flexibility exercises, endurance or aerobic exercises, and strengthening exercises. It’s important for those with osteoarthritis to consult with their doctor before embarking on any exercise routine.
Lambie says acetaminophen has been the recommended regimen for osteoarthritis for many years, but – in part because of studies like the one from the University of Bern – guidelines will likely be revamped. He suggests people suffering from osteoarthritis talk to their doctor about their treatment options, including the use of an NSAID.
“There needs to be a balance between risk and benefit,” he says.
Indian River Medical Center’s main phone number is 772-567-4311.