Systematic review of the nutritional supplements dimethyl sulfoxide (DMSO) and methylsulfonylmethane (MSM) in the treatment of osteoarthritis.

Conventional treatment of osteoarthritis (OA) with non-steroidal anti-inflammatory drugs is associated with serious gastrointestinal side effects and in view of the recent withdrawal of some cyclo-oxygenase-2 inhibitors, identifying safer alternative treatment options is needed. The objective of this systematic review is to evaluate the existing evidence from randomised controlled trials of two chemically related nutritional supplements, dimethyl sulfoxide (DMSO) and methylsulfonylmethane (MSM) in the treatment of OA to determine their efficacy and safety profile. The electronic databases [Cochrane Library, Medline, Embase, Amed, Cinahl and NeLH (1950 to November 2007)] were searched. The search strategy combined terms: osteoarthritis, degenerative joint disorder, dimethyl sulfoxide, DMSO, methylsulfonylmethane, MSM, clinical trial; double-blind, single blind, RCT, placebo, randomized, comparative study, evaluation study, control. Inclusion and exclusion criteria were applied. Data were extracted and quality was assessed using the JADAD scale. Six studies were included [evaluating a total of 681 patients with OA of the knee for DMSO (N=297 on active treatment); 168 patients for MSM (N=52 on active treatment)]. Two of the four DMSO trials, and both MSM trials reported significant improvement in pain outcomes in the treatment group compared to comparator treatments, however, methodological issues and concerns over optimal dosage and treatment period, were highlighted. No definitive conclusion can currently be drawn for either supplement. The findings from all the DMSO studies need to be viewed with caution because of poor methodology including; possible unblinding, and questionable treatment duration and dose. The data from the more rigorous MSM trials provide positive but not definitive evidence that MSM is superior to placebo in the treatment of mild to moderate OA of the knee. Further studies are now required to identify both the optimum dosage and longer-term safety of MSM and DMSO, and definitive efficacy trials.