US Pharm. 2016;41(4):43-44.
Method of Preparation: Calculate the quantity of each ingredient for the amount to be prepared. Accurately weigh or measure each ingredient. Sprinkle and disperse the xanthan gum onto about 25 mL of purified water previously heated to 70°C; set aside. Mix the mupirocin, benzyl alcohol, cetomacrogol 1000, cetyl alcohol, phenoxyethanol, and stearyl alcohol to the mineral oil previously heated to about 70°C. Pour the oil phase into the aqueous phase with constant mixing to form an emulsion. Remove from heat and cool with intermittent stirring. Add sufficient purified water to final weight and mix well. Package and label.
Use: Mupirocin 2% cream is used as a topical antibacterial agent for skin infections.
Packaging: Package in tight, light-resistant containers.
Labeling: Keep out of reach of children. Discard after ____ [time period].
Stability: A beyond-use date may be assigned based on the current edition of USP <795>.1
Quality Control: Quality-control assessment can include theoretical weight compared with actual weight, pH, specific gravity, active drug assay, color, texture-surface, texture-spatula spread, appearance, feel, rheologic properties, and physical observations.2
Discussion: Bactroban cream is not commercially available and has been discontinued by some manufacturers, so it can now be compounded to be used as prescribed. Mupirocin calcium is applied topically to the skin as a cream containing 2% mupirocin in an oil-in-water–based vehicle.
Mupirocin calcium (Bactroban, C52H86CaO18.2H2O, MW 1075.34) has a narrow spectrum of activity, primarily against gram-positive bacteria. It is used as a topical antibacterial agent in skin infections, especially impetigo, and in nasal carriage of methicillin-resistant Staphylococcus aureus. Mupirocin calcium occurs as a white to off-white, crystalline solid. It is very slightly soluble in water.1
Benzyl alcohol (C7H8O, MW 108.14) is an antimicrobial preservative, disinfectant, and solvent. Benzyl alcohol is a clear, colorless, oily liquid that has a faint, aromatic odor and a sharp, burning taste. It is soluble 1 g in 25 mL of water at room temperature and is miscible with ethanol.3
Cetomacrogol 1000 (Ceteth 20, polyoxyethylene glycol 1000 monocetyl ether) occurs as a white, waxy solid with a bland, characteristic odor that is dispersible in hot water. It has a specific gravity of 1.02 and is used as an emulsifier.4
Cetyl alcohol (C16H34O, MW 242.44) occurs as waxy, white flakes, granules, cubes, or castings. It has a faint characteristic odor and bland taste and is used as an emulsifying agent. Cetyl alcohol is freely soluble in 95% ethanol and ether and is practically insoluble in water.5
Mineral oil (heavy mineral oil, liquid paraffin, liquid petrolatum, paraffin oil, white mineral oil) is a transparent, colorless, viscous liquid that is practically tasteless and odorless when cold; when warm, it has a faint odor. It is used as an emollient, solvent, lubricant, therapeutic agent, and oleaginous vehicle. Mineral oil is practically insoluble in 95% ethanol, glycerin, and water.6
Phenoxyethanol (C8H10O2, MW 138.16) is a colorless, slightly viscous liquid that is slightly soluble in water, peanut oil, and olive oil. Phenoxyethanol is miscible with alcohol and glycerin.1 Stearyl alcohol (1-octadecanol, C18H38O, MW 270.49) occurs as unctuous, white flakes or granules with a faint, characteristic odor and a bland, mild taste. It is soluble in alcohol and insoluble in water.1
Xanthan gum (corn sugar gum) is a high-molecular-weight polysaccharide gum that occurs as a cream or white-colored, odorless, free-flowing, fine powder. It is soluble in cold or warm water. Xanthan gum is used as a stabilizing agent and, in suspensions, as a viscosity-increasing agent.7
REFERENCES
1. U.S. Pharmacopeia/National Formulary [current revision]. Rockville, MD: U.S. Pharmacopeial Convention, Inc; March 2016.
2. Allen LV Jr. Standard operating procedure for performing physical quality assessment of ointments/creams/gels. IJPC. 1998;2:308-309.
3. Storey RA. Benzyl alcohol. In: Rowe RC, Sheskey PJ, Cook WG, Quinn ME, eds. Handbook of Pharmaceutical Excipients. 7th ed. Washington, DC: American Pharmaceutical Association; 2012: 68-70.
4. Ash M, Ash I. Handbook of Pharmaceutical Additives. 3rd ed. Endicott, NY: Synapse Information Resources, Inc; 2007:522-523.
5. Unvala HM. Cetyl alcohol. In: Rowe RC, Sheskey PJ, Quinn ME, eds. Handbook of Pharmaceutical Excipients. 6th ed. London, England: Pharmaceutical Press; 2009:155-156.
6. Sheng JJ. Mineral oil. In: Rowe RC, Sheskey PJ, Quinn ME, eds. Handbook of Pharmaceutical Excipients. 6th ed. London, England: Pharmaceutical Press; 2009:445-447.
7. Shah HC, Singh KK. Xanthan gum. In: Rowe RC, Sheskey PJ, Quinn ME, eds. Handbook of Pharmaceutical Excipients. 6th ed. London, England: Pharmaceutical Press; 2009:782-785.
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