Dimethyl sulfoxide, commonly known as DMSO, is a colorless liquid. It can dissolve a broad spectrum of polar and nonpolar compounds, and mix with water and many organic solvents, making it a versatile tool. DMSO also readily penetrates biological membranes without causing damage, leading to widespread interest in its applications.
Understanding DMSO’s Chemical Identity
DMSO carries the chemical formula (CH₃)₂S=O, identifying it as an organosulfur compound. It functions as a polar aprotic solvent, meaning it can dissolve many organic and inorganic chemicals without a transferable proton. DMSO also exhibits a high boiling point of 189 °C (372 °F).
The initial synthesis of DMSO occurred in 1866, attributed to the Russian scientist Alexander Zaytsev. Industrially, DMSO is primarily derived from dimethyl sulfide, which is a byproduct of the kraft paper-making process. This conversion involves the oxidation of dimethyl sulfide with oxygen or nitrogen dioxide. As a general solvent, DMSO finds frequent use in laboratory settings for chemical reactions, especially those involving salts. Its deuterated form, DMSO-d6, is specifically employed in nuclear magnetic resonance (NMR) spectroscopy for dissolving test compounds.
Diverse Applications in Biology and Medicine
DMSO’s amphiphilic nature enables it to interact with both lipid bilayers and aqueous environments, facilitating drug transport across typically impermeable barriers. This allows it to transport various compounds into biological systems.
In biological research, DMSO acts as a cryoprotectant, preventing cell death during freezing by depressing the freezing point of water and promoting vitrification, which inhibits ice crystal formation. It works by replacing intracellular water and forming hydrogen bonds with water molecules, thereby maintaining cellular integrity during freezing and thawing cycles. In polymerase chain reaction (PCR), DMSO inhibits the formation of secondary structures in DNA templates or primers by hydrogen bonding to the major and minor grooves of DNA, thereby destabilizing the double helix. This action is especially useful for DNA templates with high guanine-cytosine (GC) content, where strong hydrogen bonding makes denaturation difficult and encourages interfering secondary structures.
In human medicine, DMSO is recognized for its topical analgesic, anti-inflammatory, and antioxidant properties. It is believed to relieve pain by blocking nerve conduction in peripheral nerve C fibers and by inactivating toxic oxygen radicals produced during tissue injury. The U.S. Food and Drug Administration (FDA) has approved DMSO for the symptomatic relief of interstitial cystitis, a chronic bladder condition. For this application, a 50% DMSO solution is instilled directly into the bladder via a catheter or syringe to reduce inflammation and relax bladder muscles.
DMSO is also incorporated into transdermal drug delivery systems, enhancing the absorption of various therapeutic agents, including anti-inflammatory drugs and antibiotics, into deeper tissues when applied topically. It achieves this by altering the structure of the stratum corneum, the skin’s outermost layer, and increasing drug solubility.
Veterinary medicine utilizes DMSO, particularly as a liniment for horses to reduce swelling, inflammation, and pain associated with injuries like strained muscles or bruises. It can be applied topically or, in systemic cases such as neurological conditions or laminitis, administered intravenously or orally to reduce inflammation and cerebral edema. Its diuretic properties help flush toxins from a horse’s system, useful in cases of poisoning.
Important Safety Considerations
While DMSO has low acute toxicity, with a higher median lethal dose than ethanol, its properties necessitate careful handling. A primary concern stems from its ability to enhance the absorption of substances through the skin. This means that contaminants, toxins, or other medications present on the skin can be carried into the body, potentially leading to unexpected systemic effects.
DMSO can also interact with other medications, increasing their effects. For example, it can enhance the effects of blood thinners, increasing the risk of bruising and bleeding. It can also heighten the effects of steroids, heart medicines, and sedatives. Using DMSO with certain chemotherapy drugs can reduce their effectiveness.
A common and distinctive side effect observed after skin contact with DMSO is a garlic-like taste in the mouth. This taste is attributed to the metabolism of DMSO into other compounds, particularly dimethyl sulfide (DMS), which is then eliminated through the breath and skin. This effect can manifest within minutes of exposure and may persist for several hours.