VIENNA — Transdermal fentanyl brought effective pain relief to patients with advanced knee or hip osteoarthritis in a large randomized, double-blind, placebo-controlled trial, Jozef Vojtassak, M.D., reported at the annual European congress of rheumatology.
Fentanyl patches have previously been shown to be effective for a variety of types of chronic nonmalignant pain, including that associated with osteoarthritis; however, until now the evidence has come largely from open-label studies, according to Dr. Vojtassak of Comenius University, Bratislava, Slovakia.
He reported on 416 patients awaiting knee or hip replacement surgery who were randomized to transdermal fentanyl (Durogesic) or placebo patches in a 6-week double-blind study followed by a week-long taper. All had previously shown an inadequate response to weak opioids. None had received strong opioids within 4 weeks of enrollment.
The starting dose of fentanyl was 25 mcg/hour. It could gradually be raised to 100 mcg/hour as required. Patches were changed every 72 hours. Allowable supplemental pain medication consisted of nonsteroidal anti-inflammatory agents, used by more than two-thirds of patients, and acetaminophen, used at dosages of up to 4 g/day by 27%.
Of note, 57% of participants withdrew from the study prematurely, with roughly equal numbers of dropouts in both study arms. Their reasons for quitting, however, were quite different. Fifteen patients in the fentanyl arm withdrew because of insufficient treatment efficacy, compared with 66 in the placebo group. On the other hand, 62 patients taking fentanyl quit due to adverse events—chiefly nausea and vomiting—compared with 20 patients in the placebo group, he said at the meeting, which was sponsored by the European League Against Rheumatism.
The primary study end point was change in mean pain visual analog scores recorded by patients in a daily pain diary. From a baseline self-rated score of 73 out of a possible 100, fentanyl-treated patients had a mean 23.4-point decrease, significantly better than the 17.9-point reduction with placebo. Morning and evening pain improved by 19%–20% in the fentanyl arm, compared with a 14% improvement with placebo.
Pain on walking was rated 25% better than at baseline in fentanyl-treated patients with knee osteoarthritis, and 15% better in placebo-treated patients. Similarly, fentanyl-treated patients with hip osteoarthritis rated their pain on walking as 20% improved over baseline, which was significantly better than the nearly 13% improvement among controls.
Measures of functional improvement by the Western Ontario and McMaster Universities Osteoarthritis Index trended in favor of the fentanyl group, a benefit that fell just short of statistical significance. The study was sponsored by Janssen Pharmaceutica.