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Trial of tramadol/acetaminophen tablets for osteoarthritis pain in subjects receiving a COX-2 nonsteroidal antiinflammatory drug.

Emkey, et al1 describe the effectiveness and safety of tramadol combined with acetaminophen as treatment for symptomatic osteoarthritis (OA) of the knee or hip in patients already receiving a cyclooxygenase-2 (COX-2) selective drug. The study conclusions have deficiencies, in our opinion, that we believe warrant comment. Having a drug combination of 2 analgesics, tramadol and acetaminophen, as the treatment arm makes it very difficult to sort out which one of the 2 was beneficial. This is gently commented on in an accompanying editorial2. We understand that the study was supported by the manufacturer of the drug combination, but a third arm with either acetaminophen or tramadol alone would help focus on which drug was contributing the most to the analgesia and the side effects. We were also concerned about the short duration of the study in patients with chronic joint pain. Three months, the duration of this study, is not a very long time for patients with chronic pain. We were especially concerned about adverse events and we conclude that the addition of tramadol/acetaminophen combination to a COX-2 drug might not be safe. After all, in Table 3, fully 18 out of 153 patients receiving the drug combination had somnolence, 23 had nausea, 20 complained of constipation, 10 had fatigue, 4 experienced vomiting, and 10 had dizziness. These reported adverse events were much less common in the placebo group. We understand that some of these reported events might be very mild and several may be occurring in the same patients. The average age of the study patients was only 61 years and it is likely that in an older population of patients with OA, side effects such as somnolence, for instance, might occur even more frequently and be more severe. Our patients with chronic OA are generally older than 61 years. Neither the authors1 nor Dr. Altman2 mention the cost of this drug combination. The mean tramadol/acetaminophen use was 4.1 tablets in the study. At our university pharmacy, 100 Ultracet® tablets retail for $115, or more than $4 a day for the average patient in this study. Of course this is in addition to the COX-2 drug. We don’t mean to be critical about this helpful study that was performed well. A trial of tramadol with acetaminophen might be helpful in OA pain, but side effects and cost are important issues that need to be discussed more fully, and longer term use of this drug combination is needed to verify efficacy.