US Pharm. 2014 ;39(6):54-55.



Method of Preparation: Calculate the quantity of each ingredient for the amount to be prepared. Accurately weigh or measure each ingredient. Mix together the methyl salicylate, menthol, and thymol to form a liquid. Gently heat the anhydrous lanolin just until it liquefies. Incorporate the vitamin E acetate, olive oil, glycerin, and coconut oil (previously heated gently until fluid) and mix well. Remove the liquid mixture from heat, incorporate the aromatic mixture, let cool, and mix well. Package and label.

Use: This preparation has been used in the treatment of podiatric disorders.

Packaging: Package in tight, light-resistant containers.

Labeling: Keep out of reach of children. Discard after ____ [time period]. For external use only.

Stability: A beyond-use date of up to 6 months may be used for this preparation.1

Quality Control: Quality-control assessment can include theoretical weight compared with actual weight, specific gravity, color, texture, appearance, feel, rheologic properties, and physical observations.2

Discussion: Vitamin E is a term applied to a large number of natural and synthetic compounds, the most important of which are the tocopherols. Vitamin E is practically odorless and tasteless. The alpha tocopherol acetates occur as clear, yellow, or greenish yellow, viscous oils. The esters are stable to air and light, but are unstable to alkali.1 ,3

Olive oil is a pale yellow or light greenish yellow, oily liquid with a slight, characteristic odor and taste. It is slightly soluble in alcohol. Olive oil has a specific gravity between 0.910 and 0.915.1,4

Coconut oil is the refined, fixed oil of the seeds of Cocos nucifera Linné (fam. Palmae). It occurs as a clear, white to light yellow or tan, viscous liquid. Coconut oil is very slightly soluble in alcohol and practically insoluble in water. Its melting point is between 23°C and 26°C.1

Glycerin (1,2,3- propanetriol, glycerol) occurs as a clear, colorless, odorless, viscous, hygroscopic liquid with a specific gravity of about 1.25 and a melting point of 17.8°C. It is miscible with water, methanol, and 95% ethanol, practically insoluble in oils and chloroform, and slightly soluble in acetone.5

Methyl salicylate (C8H8O3, MW 152.15) occurs as a colorless, yellowish, or reddish liquid with the characteristic odor and taste of wintergreen. It is slightly soluble in water and soluble in alcohol and glacial acetic acid. Methyl salicylate has a specific gravity between 1.170 and 1.185, and its refractive index is between 1.535 and 1.538 at 20°C.1 ,6

Menthol (C10H20O, MW 156.27) occurs as colorless, hexagonal crystals, usually needlelike or in fused masses, or as a crystalline powder. It has a pleasant, peppermint-like odor. Menthol is slightly soluble in water and highly soluble in alcohol. It is freely soluble in fixed and volatile oils, and it melts between 41°C and 44°C.7

Thymol (C10H14O, MW 150.22) occurs as colorless, often large, crystals or as a white, crystalline powder with an aromatic, thymelike odor and a pungent taste. It is very slightly soluble in water and freely soluble in alcohol and olive oil. Thymol is used as an antifungal and antibacterial agent, commonly in a 0.2%-1.0% concentration.8

Lanolin, anhydrous (wool fat), occurs as a yellow, tenacious, unctuous mass with a slight, characteristic odor. It is insoluble in water and sparingly soluble in cold ethanol (95%). When melted, lanolin is a clear or almost clear, yellow liquid. Its melting point is about 38°C to 44°C. Lanolin is used as a hydrophobic emollient vehicle.9

REFERENCES

1. U.S. Pharmacopeia 36/National Formulary 31. Rockville, MD: U.S. Pharmacopeial Convention, Inc; 2013:335-398,1253,1266-1267,1272,1275,1293,1295-1296.
2. Allen LV Jr. Standard operating procedure for performing physical quality assessment of ointments/creams/gels. IJPC. 1998 ;2:308-309.
3. Sweetman SC. Martindale: The Complete Drug Reference. 35th ed. London, England: Pharmaceutical Press; 2007:1828-1830.
4. Reilly WJ Jr. Pharmaceutical necessities. In: Gennaro AR, ed. Remington: The Science and Practice of Pharmacy. 19th ed. Easton, PA: Mack Publishing Co; 1995:1400.
5. Alvarez-Nunez FA, Medina C. Glycerin. In: Rowe RC, Sheskey PJ, Quinn ME, eds. Handbook of Pharmaceutical Excipients. 6th ed. Washington, DC: American Pharmaceutical Association; 2009:283-286.
6. Reynolds JEF, ed. Martindale: The Extra Pharmacopoeia. 30th ed. London, England: Pharmaceutical Press; 1993:24.
7. Langdon BA, Mullarney MP. Menthol. In: Rowe RC, Sheskey PJ, Quinn ME, eds. Handbook of Pharmaceutical Excipients. 6th ed. Washington, DC: American Pharmaceutical Association; 2009:433-435.
8. Harvey SC. Topical drugs. In: Osol A, ed. Remington’s Pharmaceutical Sciences. 16th ed. Easton, PA: Mack Publishing Co; 1980 : 1112.
9. Bonner MC. Lanolin. In: Rowe RC, Sheskey PJ, Quinn ME, eds. Handbook of Pharmaceutical Excipients. 6th ed. Washington, DC: American Pharmaceutical Association; 2009:378-380.

To comment on this article, contact rdavidson@uspharmacist.com.