Monothioglycerol

• USP–NFMonothioglycerol

Thioglycerol; 1-thioglycerol; α-monothioglycerol; 3-mercapto-1,2-propanediol; 3-sulfanylpropane-1,2-diol

3-Mercaptopropane-1,2-diol · [96-27-5]

UNII AAO1P0WSXJ · PubChem CID 7291

C3H8O2S · 108.16

Antioxidant, chelating agent

Typical concentrations: — · Dosage forms: Sterile (parenteral/ophthalmic)

Used as an antioxidant and stabiliser in parenteral preparations, usually at 0.1–1.0% w/v. It has also been used in some topical and cosmetic products.

A colourless or pale yellow, viscous, hygroscopic liquid with a slight sulfidic odour.

Specific gravity

1.241–1.250 at 25 °C

Refractive index

1.521–1.526 at 20 °C

pH

3.5–7.0 (10% w/v aqueous solution)

Solubility

miscible with water and ethanol (95%); practically insoluble in ether

Oxidises on exposure to air, especially in alkaline solution and in the presence of metal ions. Store in an airtight container, protected from light, in a cool place.

Incompatible with oxidising agents. As a thiol it can react with metal ions and form disulfides, and may interact with drugs or proteins containing disulfide bonds.

Prepared by reacting 3-chloro-1,2-propanediol (or glycidol) with a source of hydrogen sulfide, such as sodium hydrogen sulfide.

Used in parenteral products at low concentrations without significant toxicity being reported. The neat liquid is irritant to skin and eyes, and skin sensitisation has been reported.

Irritant: wear gloves and eye protection and handle in a well-ventilated area to avoid the odour and vapour.

Included in the FDA Inactive Ingredient Database (intramuscular, intravenous and subcutaneous injections).

Thioglycolic acid; cysteine; sodium metabisulfite; sodium formaldehyde sulfoxylate; methionine.

Its antioxidant activity is consumed as it oxidises, so headspace oxygen should also be minimised (for example by nitrogen flushing) and the residual level monitored on stability.