The present study, using I4C-DMSO, established the systemic and local load and distribution of topically applied DMSO in adjuvant arthritic rats. Under equivalent conditions, the antiinflammatory effects (systemic and local) of topical DMSO treatments were compared with a topical treatment of a control vehicle or of indomethacin, a known effective antiinflammatory agent. No significant systemic or local antiinflammatory effect of topical DMSO was seen in the adjuvant arthritic rats. Indomethacin, applied topically, had a significant systemic antiinflammatory effect; however, no significant local antiinflammatory effect of indomethacin was observed.Dimethylsulfoxide (DMSO) has been and still is a controversial chemical with respect to its medical usage in inflammatory diseases. Its chemical properties, multiple usage, toxicology, absorption, distribution, and metabolism have been reported (1,2). Indomethacin, in contradistinction to DMSO, is a proven nonsteroidal antiinflammatory agent. Its chemical properties, clinical pharmacology, usage, and effectiveness have been described (3,4).Injection of killed and dried Mycobacterium butyricum suspended in oil produces adjuvant disease in rats. This disease resembles rheumatoid arthritis (RA) and Reiter's syndrome in a number of clinical and pathologic characteristics (5-9). Several experiments have been conducted on the antiinflammatory action of DMSO in adjuvant arthritis in rats. One report suggests that DMSO, whether applied topically (on the neck or the paw) or orally, produces a significant reduction in paw volume due to inflammation, suggesting the effect may be systemic (10). Others have reported a more pronounced effect of DMSO when applied locally by topical application than when given orally, suggesting there may be a significant local antiinflammatory effect (1 1,12). In single-blind tests in RA patients, there was a decrease in pain and increase in joint range of motion in one study (13) but not in another (14), and in neither study was there a significant effect on joint swelling (13,14). In a doubleblind study in RA patients, no benefit of DMSO over placebo treatment was seen (15).To further evaluate the local and systemic antiinflammatory effects of DMSO, we undertook the following study in which groups of rats with adjuvant arthritis were topically administered DMSO, indomethacin, or a control preparation, and the results analyzed.
MATERIALS AND METHODSPreparation of Freund's adjuvant. Modified Freund's adjuvant (MFA) was prepared by mixing 8 mg of pulverized, dried, heat-kiiled Mycohactcriidm bldfyrjc,,m (Lot #663075, Difco Laboratories, Detroit, MI) per ml of mineral oil (USP #350) in an Omni mixer (DuPont Instruments, Newtown, CT) for approximately 45 minutes, until a smooth, semiprepared immediately prior to the injection into the rat. During the entire injection period, the MFA mixture was constantly stirred.