Benzocaine 2% and Vitamins A and D Ointment

US Pharm. 2012;37(11):37-38.

Method of Preparation: Calculate the quantity of each ingredient for the amount to be prepared. Accurately weigh/measure each ingredient. Pulverize the benzocaine to a fine powder; mix with about 20 g of white petrolatum. Pulverize the vitamin D to a fine powder, add to mixture, and mix well. Incorporate the vitamin A into the anhydrous lanolin. Combine the two mixtures; mix well. Add sufficient white petrolatum to final weight; mix well. Package and label.

Use: Benzocaine and vitamins A and D ointment may be used to treat burns, sunburn, windburn, and minor skin irritations. The formula may be modified for individual patient needs.

Packaging: Package in tight, light-resistant containers.¹

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

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, pH, specific gravity (SG), active drug assay, color, texture–surface, texture–spatula spread, appearance, feel, rheologic properties, and physical observations.²

Discussion: This preparation is similar to a formerly available commercial product (Morusan) containing benzocaine 2%, cod liver oil concentrate, lanolin, and petrolatum. This formula lacks the odor of cod liver oil, as vitamins A and D are used in their USP form.

Benzocaine (ethyl aminobenzoate, C₉H₁₁NO₂, MW 165.19) occurs as small, white crystals or as a white, crystalline, odorless powder. A topical anesthetic of the ester type with low systemic toxicity, it exhibits local anesthetic properties when placed on the tongue. It is stable in air and is slightly soluble in water (1:2,500), freely soluble in alcohol (1:5-8) and ether (1:4), and sparingly soluble in almond and olive oils (1:30-50). It dissolves in dilute acids. Protect it from light and store in tight containers.³

Vitamin A consists of retinol or its esters formed from edible fatty acids, principally acetic and palmitic acids. It is used to treat vitamin A deficiencies and various skin disorders. In liquid form, it occurs as a light yellow to red oil that may solidify upon refrigeration. It is insoluble in water and glycerin, and soluble in dehydrated alcohol and vegetable oils. Store in airtight containers (preferably in an atmosphere of an inert gas) and protect from light.⁴

Vitamin D (ergocalciferol, Deltalin, Drisdol, Calciferol, C₂₈H₄₄O, MW 396.65) occurs as white, odorless crystals that are soluble in alcohol and fatty oils, but insoluble in water. It is a vitamin D analogue used as a dietary supplement and to treat rickets, hypophosphatemia, hypoparathyroidism, and various skin disorders. It is affected by air and light and should be stored at room temperature.³

Lanolin (wool fat), a yellow, tenacious, unctuous mass with a slight, characteristic odor, is obtained from sheep’s wool and cleaned, decolorized, and deodorized. It is widely used in cosmetics and topical formulations and is useful when an aqueous ingredient must be incorporated into an oleaginous base, as it can readily absorb about equal its own weight of water. Insoluble in water, it mixes without separation with about twice its weight of water. It is sparingly soluble in cold ethanol (95%) and freely soluble in chloroform and ether. When melted, it is a clear or almost clear yellow liquid. It melts at about 38°C to 44°C and has a density of about 0.94 g/mL. It may undergo autoxidation during storage, so not more than 0.02% of a suitable antioxidant may be added. It produces emollient preparations that penetrate the skin and can facilitate drug absorption. Store anhydrous lanolin in light-resistant, well-closed containers that are well filled to minimize degradation. When exposed to heat, it may darken and develop a strong rancid-like odor. When used in sterile products, it can be dry-heat sterilized at 150°C.⁵

White petrolatum (white petroleum jelly, white soft paraffin) is a white-colored, translucent, soft, unctuous mass that is inert, odorless, and tasteless. A mixture of semisolid saturated hydrocarbons obtained from petroleum, it is used primarily in topical pharmaceutical formulations in emollient creams, topical emulsions, and topical ointments. It has an SG of about 0.815 to 0.880 and melts between 38°C and 60°C. It is practically insoluble in ethanol, glycerin, and water, but is soluble in chloroform and most fixed and volatile oils. It is stable, but upon exposure to light it may discolor due to oxidation of some impurities in the product. Oxidation can be minimized by adding a suitable antioxidant, such as butylated hydroxyanisole, butylated hydroxytoluene, or alpha-tocopherol. Heating white petrolatum above its melting range (about 70°C) for extended times should be avoided, but it can be sterilized by dry heat.⁶

REFERENCES

1. U.S. Pharmacopeia 35/National Formulary 30. Rockville, MD: U.S. Pharmacopeial Convention, Inc; 2012:334-386.
2. Allen LV Jr. Standard operating procedure for performing physical quality assessment of ointments/creams/gels. IJPC. 1998;2:308-309.
3. Allen LV Jr, ed. Remington: The Science and Practice of Pharmacy. 22nd ed. Philadelphia, PA: Pharmaceutical Press;1253-1255,1427.
4. Sweetman SC, ed. Martindale: The Complete Drug Reference. 35th ed. London, England: Pharmaceutical Press; 2007:1808-1812.
5. Shah HC, Singh KK. Lanolin. In: Rowe RC, Sheskey PJ, Cook WG, Fenton ME, eds. Handbook of Pharmaceutical Excipients. 7th ed. Washington, DC: American Pharmaceutical Association; 2012:429-431.
6. Lambert WJ. Petrolatum. In: Rowe RC, Sheskey PJ, Cook WG, Fenton ME, eds. Handbook of Pharmaceutical Excipients. 7th ed. Washington, DC: American Pharmaceutical Association; 2012:547-549.

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