By Don Bottoni, RPh, FACA, PCCA Clinical Compounding Pharmacist

Dimethyl sulfoxide (DMSO) is an interesting substance, and it has many uses in the pharmacy world. It is classified as an aprotic solvent, which means that it does not contain any hydrogen atoms and is not capable of being a proton donor. This property makes it an ideal solvent in which most chemicals are stable. It is miscible with many other solvents as well, including water. It has a high boiling point, so it will not rapidly evaporate at room temperature. It can freeze at temperatures around 68° F. If a pharmacy receives a shipment of DMSO that contains crystals, simply place the container in a warm water bath, and the crystals will dissolve. It is best not to use the DMSO until the crystals have dissolved and the container is shaken well. If the crystals are not dissolved, the liquid portion can contain a higher concentration of impurities.

Among other applications, DMSO has historically been used in compounded creams and gels as a permeation enhancer, though modern compounding bases such as Lipoderm® and PermE8® Anhydrous Gel provide superior delivery without some of the harsh properties of DMSO. Despite its prevalence, however, not all DMSOs are created equal, and there are a couple easy ways to determine if yours might be of questionable quality.

Test 1
Does the DMSO you are using have an odor? If it does, it may mean that you are using an inferior quality product. There are several grades of this chemical that are used in different industries and for various purposes, including analytical applications and the manufacturing of semiconductor devices. However, a high-quality, USP-grade DMSO — which is what we must use in pharmacy compounding — should be virtually odorless.

Test 2
Recently, we have heard from some compounders that crystals are forming when they add their DMSO to water. DMSO is a nontoxic solvent obtained as a by-product of the paper-making industry, and lower grades of it may contain other distillates and contaminants that are not freely soluble in water. Therefore, if your DMSO is forming crystals when you add it to water, it may be because of a higher level of impurities. This should not happen with a high-quality, USP-grade DMSO.

Many years ago, PCCA set the standard by finding the highest grade chemicals for the compounding pharmacies we work with. This means we offer USP-grade DMSO that contains few if any impurities and is almost odorless. It does not form crystals when added to water. This high purity may help reduce any irritations when used in topical preparations as well. We compounders are mandated by USP to use the highest grade chemicals possible. Using USP-grade DMSO helps to ensure that you are following USP guidelines and that you are compounding a quality product.

PCCA members can learn more by reading the document Not All DMSOs Are the Same on our Members-Only Website. They can also see more details on the proper thawing procedure for DMSO.

Don Bottoni, RPh, FACA, joined the staff of PCCA in January 2010 after 40 years of practice in independent pharmacies. He graduated from Texas Tech University in 1966 with a BA in chemistry and The University of Texas College of Pharmacy with a BS in pharmacy in 1969. Don’s areas of interest include nutrition, sterile compounding, bioidentical hormone replacement therapy and men’s health. Don has been a presenter at many PCCA International Seminars and at University of Texas continuing-education seminars, and he taught several classes on nutrition for PCCA in the mid-1990s.