Randomized Controlled Trial
Tramadol hydrochloride extended-release once-daily in the treatment of osteoarthritis of the knee and/or hip: a double-blind, randomized, dose-ranging trial.
Am J Ther. 2011 May 1;18(3):216-26.
Randomized Controlled Trial
Analgesic efficacy and safety of tramadol/ acetaminophen combination tablets (Ultracet) in treatment of chronic low back pain: a multicenter, outpatient, randomized, double blind, placebo controlled trial.
J Rheumatol. 2004 Dec 1;31(12):2454-63.
Randomized Controlled Trial
Comparative clinical trial of S-adenosylmethionine versus nabumetone for the treatment of knee osteoarthritis: an 8-week, multicenter, randomized, double-blind, double-dummy, Phase IV study in Korean patients.
Clin Ther. 2009 Dec 1;31(12):2860-72.