Method of Preparation: Calculate the quantity of each ingredient for the amount to be prepared. Accurately weigh or measure each ingredient. Blend together the citric acid solution, disodium phosphate solution, and polyethylene glycol (PEG) 400. Add the povidone-iodine and mix well. Add the mineral oil and mix well. Cool to 5°C to 8°C; add the Pluronic F127 and mix until dissolved. Keep cool until air bubbles disappear. Package and label.
Use: Povidone-iodine 10% gel-cream is used as a topical antibacterial and antifungal.
Packaging: Package in tight, light-resistant containers.
Labeling: For external use only. Keep out of reach of children. Discard after ____ [time period].
Stability: A beyond-use date of up to 30 days may be used for this preparation.1
Quality Control: Quality-control assessment may include theoretical weight compared with actual weight, pH (about 4.5), specific gravity, active drug assay, color, texture–surface, texture–spatula spread, appearance (brown cream), feel, rheologic properties, and physical observations (viscosity of about 113,000 mPa·s).2
Discussion: Povidone-iodine (Betadine) is a complex of iodine with povidone. It contains not less than 9.0% and not more than 12.0% of available iodine, calculated on the dried basis. It occurs as a yellowish-brown to reddish-brown, amorphous powder with a slight, characteristic odor. Its solution is acid to litmus. Povidone-iodine is soluble in water and in alcohol. It loses not more than 8.0% of its weight upon drying. It is an external antiseptic with a broad microbicidal spectrum against bacteria, fungi, viruses, protozoa, and yeasts. This gel has about 1.0% available iodine.1
Citric acid (citric acid monohydrate, C6H8O7.H2O) occurs as colorless or translucent crystals or as a white, crystalline, efflorescent powder that is odorless and has a strong, tart, acidic taste. The pH of a 1% w/v aqueous solution is about 2.2. One gram is soluble in less than 1 mL of water and 1.5 mL of ethanol.3
Sodium phosphate, dibasic, is available in an anhydrous form (MW 141.96) and as a dihydrate (MW 177.98), heptahydrate (MW 268.03), and dodecahydrate (MW 358.08). It is used as a buffering agent and a sequestering agent. The dodecahydrate occurs as colorless or transparent crystals; the hydrated forms are efflorescent, especially the dodecahydrate. The typical pH of a 1% aqueous solution of the anhydrous form is about 9.1. Sodium phosphate, dibasic, is highly soluble in water (dodecahydrate, 1 in 3), but is practically insoluble in ethanol.4
PEG (Carbowax, polyoxyethylene glycol) is an addition polymer of ethylene oxide and water. PEG 400 is a clear, colorless or slightly yellow-colored, viscous liquid with a slight, characteristic odor and a bitter, slightly burning taste. PEG 400 is miscible in all ratios with other PEGs and is soluble in acetone, alcohols, glycerin, and glycols.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 has a specific gravity of 0.845 to 0.905. It is practically insoluble in 95% ethanol, glycerin, and water. Mineral oil is miscible with volatile and fixed oils, with the exception of castor oil. To promote miscibility/solubilization, a small amount of a suitable surfactant may be added. When it is exposed to heat and light, mineral oil undergoes autocatalytic oxidation, resulting in the formation of peroxides. Stabilizers, such as butylated hydroxyanisole, butylated hydroxytoluene, and alpha-tocopherol, may be used as antioxidants to retard the oxidative process.6
The poloxamers are a series of closely related block copolymers of ethylene oxide and propylene oxide that are used as emulsifying agents, solubilizing agents, and wetting agents. Pluronic F127 occurs as a white-colored, waxy powder that is practically odorless and tasteless. The pH of a 2.5% w/v aqueous solution is in the range of 6.0 to 7.4. It melts at about 56°C and is freely soluble in water, alcohol, and isopropyl alcohol.7
REFERENCES
1. U.S. Pharmacopeia 35/National Formulary 30. Rockville, MD: U.S. Pharmacopeial Convention, Inc; 2012:334-386,1140,4381-4383.
2. Allen LV Jr. Standard operating procedure for performing physical quality assessment of ointments/creams/gels. IJPC. 1998;2:308-309.
3. Amidon GE. Citric acid monohydrate. In: Rowe RC, Sheskey PJ, Cook WG, Fenton ME, eds. Handbook of Pharmaceutical Excipients. 7th ed. Washington, DC: American Pharmaceutical Association; 2012:193-196.
4. Kearney AS. Sodium phosphate, dibasic. In: Rowe RC, Sheskey PJ, Cook WG, Fenton ME, eds. Handbook of Pharmaceutical Excipients. 7th ed. Washington, DC: American Pharmaceutical Association; 2012:752-754.
5. Wallick D. Polyethylene glycol. In: Rowe RC, Sheskey PJ, Quinn ME, eds. Handbook of Pharmaceutical Excipients. 6th ed. Washington, DC: American Pharmaceutical Association; 2009:517-522.
6. Sheng JJ. Mineral oil. In: Rowe RC, Sheskey PJ, Quinn ME, eds. Handbook of Pharmaceutical Excipients. 6th ed. Washington, DC: American Pharmaceutical Association; 2009:445-447.
7. Collett JH. Poloxamer. In: Rowe RC, Sheskey PJ, Quinn ME, eds. Handbook of Pharmaceutical Excipients. 6th ed. Washington, DC: American Pharmaceutical Association; 2009:506-509.
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