Figure 1: DMSO gel viscosity as a function of polymer loading. (MARTIN POOLE/GETTY IMAGES)
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For highly viscous gel products, loading levels of 1.5–2.0 wt% are required, and it may be helpful to warm the product (~50
°C) during the mixing process. Carbomer-type thickening agents (e.g., Carbopol) are especially recommended for use with DMSO
for their high clarity and gel stability. Figure 1 provides viscosity data at varying loading levels for Carbopol 941.
Table IV: Miscellaneous excipient solubilities in dimethyl sulfoxide.*
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Carbohydrates and miscellaneous excipients.
Some carbohydrates are freely soluble in DMSO (e.g., β- and D-lactose, sucrose). Table IV provides solubility data for various
polymeric excipient products, carbohydrates, and some miscellaneous materials.
Consideration of packaging components.
DMSO interacts physically with many polymeric materials (swelling, dissolution). As such, high-density polyethylene, high-density
polypropylene, and polytetrafluoroethylene are the only materials suitable for packaging a product containing high levels
of DMSO. Product formulations using DMSO with other cosolvents or ingredients should perform package testing to confirm compatibility.
Product odor.
Dimethyl sulfoxide, USP, PhEur is a highly pure pharmaceutical product and does not have the odor that has been associated
with some industrial materials. When purified, DMSO is essentially odorless.
Regulatory affairs
Compendial status and manufacturing aspects.
Three monographs exist in the 2005 USP–NF that reference DMSO (19). These are dimethyl sulfoxide gel, dimethyl sulfoxide irrigation, and dimethyl sulfoxide topical
solution. A monograph is established in the European Pharmacopoeia under dimethyl sulfoxide (20).
Dimethyl sulfoxide USP, PhEur is manufactured in the US under Q7 good manufacturing guidelines established by the International
Conference on Harmonization (ICH) for APIs. These guidelines have been adopted by FDA. The chemistry, manufacturing, and
controls (CMC) of DMSO are described in a type II drug master file on file with FDA and Health Canada. Applicants may reference the drug master file through its holder, Gaylord Chemical Co. LLC. Dimethyl sulfoxide USP, PhEur
is certified kosher parve.
Dimethyl sulfoxide USP, PhEur does not hold generally regarded as safe (GRAS) status as defined in sections 201(s) and 409
of the US Federal Food, Drug, and Cosmetic Act. As such, the product is not intended for food use and is subject to premarket
review in food applications. DMSO has no existing food applications.
As provided in its "Q3C Impurities: Residual Solvents" guidelines, ICH further designates DMSO a Class 3 residual solvent
when used in the manufacture of pharmaceutical products. Class 3 solvents are those considered to represent a low toxic potential
(21).
Historical aspects.
Any discussion of DMSO in pharmaceutical applications would be incomplete without mentioning the "wonder drug" status defined
for DMSO in the public and lay press in the 1960s and 1970s (22). As important, the public's fascination with—and in some
cases, abuse of—DMSO has undoubtedly influenced the approval process for formulated drug products that contain it.
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