Functional Category
Emollient; emulsifying agent; solubilizing agent; stabilizing agent; sustained-release agent; tablet and capsule lubricant.
Applications in Pharmaceutical Formulation
The many varieties of glyceryl monostearate are used as nonionic emulsifiers, stabilizers, emollients, and plasticizers in a variety of food, pharmaceutical, and cosmetic applications. It acts as an effective stabilizer, that is, as a mutual solvent for polar and nonpolar compounds that may form water-in-oil or oil-in-water emulsions.(1,2) These properties also make it useful as a dispersing agent for pigments in oils or solids in fats, or as a solvent for phospholipids, such as lecithin. Glyceryl monostearate has also been used in a novel fluidized hot-melt granulation technique for the production of granules and tablets.(3) Glyceryl monostearate is a lubricant for tablet manufacturing and may be used to form sustained-release matrices for solid dosageforms.(4–6) Sustained-release applications include the formulation of pellets for tablets(7) or suppositories,(8) and the preparation of a veterinary bolus.(9) Glyceryl monostearate has also been used as a matrix ingredient for a biodegradable, implantable, controlledrelease dosage form.(10) When using glyceryl monostearate in a formulation, the possibility of polymorph formation should be considered. The aform is dispersible and foamy, useful as an emulsifying agent or preservative. The denser, more stable, b-form is suitable for wax matrices. This application has been used to mask the flavor of clarithromycin in a pediatric formulation.(11)
Description
While the names glyceryl monostearate and mono- and diglycerides are used for a variety of esters of long-chain fatty acids, the esters fall into two distinct grades: 40–55 percent monoglycerides The PhEur 6.0 describes glyceryl monostearate 40–55 as a mixture of monoacylglycerols, mostly monostearoylglycerol, together with quantities of di- and triacylglycerols. It contains 40–55% of monoacylglycerols, 30–45% of diacylglycerols, and 5–15% of triacylglycerols. This PhEur grade corresponds to mono- and di-glycerides USP– NF, which has similar specifications (not less than 40% monoglycerides). 90 percent monoglycerides The USP32–NF27 describes glyceryl monostearate as consisting of not less than 90% of monoglycerides of saturated fatty acids, chiefly glyceryl monostearate (C21H42O4) and glyceryl monopalmitate (C19H38O4). The commercial products are mixtures of variable proportions of glyceryl monostearate and glyceryl monopalmitate. Glyceryl monostearate is a white to cream-colored, wax-like solid in the form of beads, flakes, or powder. It is waxy to the touch and has a slight fatty odor and taste.
Stability and Storage Conditions
If stored at warm temperatures, glyceryl monostearate increases in acid value upon aging owing to the saponification of the ester with trace amounts of water. Effective antioxidants may be added, such as butylated hydroxytoluene and propyl gallate. Glyceryl monostearate should be stored in a tightly closed container in a cool, dry place, and protected from light.
Incompatibilities
The self-emulsifying grades of glyceryl monostearate are incompatible with acidic substances.
Safety
Glyceryl monostearate is widely used in cosmetics, foods, and oral and topical pharmaceutical formulations, and is generally regarded as a nontoxic and nonirritant material. LD50 (mouse, IP): 0.2 g/kg(13)