Piroxicam 0.5% and Dexpanthenol 5% Topical Gel

US Pharm. 2013;38(6):66-67.

Method of Preparation: Calculate the quantity of each ingredient for the amount to be prepared. Accurately weigh or measure each ingredient. Heat the propylene glycol to 70°C to 80°C. Add the piroxicam and dexpanthenol; mix well. Add the ethanol and Pluronic F127; mix well. Add about 25 mL of the water as hot water (70°C), adjust the pH with trolamine to about 7, and add the remaining water to the final weight of 100 g. Cool to room temperature and allow the bubbles to escape. Adjust the pH to about 8; then package and label.

Use: Piroxicam and dexpanthenol gel has been used for its antipruritic and anti-inflammatory properties.

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 can include theoretical weight compared with actual weight, pH, specific gravity, active drug assay, color, clarity, texture–surface, texture–spatula spread, appearance, feel, rheologic properties, and physical observations.²

Discussion: Piroxicam (Feldene, C₁₅H₁₃N₃O₄S, MW 331.35) occurs as an off-white to light tan or light yellow, odorless powder. It forms a monohydrate that is yellow. Piroxicam is very slightly soluble in water, dilute acids, and most organic solvents. It is slightly soluble in alcohol and in aqueous alkaline solutions.¹

Propylene glycol (C₃H₈O₂) occurs as a clear, colorless, viscous, practically odorless liquid with a sweet taste somewhat resembling glycerin. It has a specific gravity of 1.038 g/mL and is miscible with 95% ethanol, glycerin, and water. Propylene glycol is used as a humectant, preservative, and solvent or cosolvent.³

Dexpanthenol (C₉H₁₉NO₄, MW 205.25) occurs as a clear, viscous, somewhat hygroscopic liquid with a slight, characteristic odor. It is freely soluble in water, alcohol, and propylene glycol and slightly soluble in glycerin. Some crystallization may occur upon standing. Dexpanthenol should be stored in airtight containers. It has been used topically in 2% to 5% concentrations in the treatment of various minor skin disorders.⁴

Alcohol (ethyl alcohol, ethanol, grain alcohol, C₂H₅OH, MW 46.07) is a clear, colorless, mobile and volatile liquid with a slight, characteristic odor and a burning taste. It is used as an antimicrobial preservative, as a disinfectant, and as a solvent in injectable and oral liquids and topical products. Alcohol USP refers to 95% ethanol, and dehydrated alcohol refers to 99.5% alcohol. Alcohol’s specific gravity is between 0.812 and 0.816, and its boiling point is 78.15°C. It is miscible with glycerin and water and should be stored in a cool place.⁵

Trolamine (TEA, triethanolamine) is an alkalizing and emulsifying agent. It occurs as a variable mixture of alkanolamines and is a clear, colorless to pale yellow-colored, viscous liquid with a slight ammoniacal odor. Its specific gravity is about 1.120 to 1.128 g/mL and it has a pH of 10.5 in a 0.1N aqueous solution. Trolamine is highly hygroscopic, melts at 20°C to 21°C, and boils at 335°C. It is miscible with water, 95% ethanol, methanol, and acetone, and it is soluble in chloroform.⁶

The poloxamers, including Pluronic F127, 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. They are available in different grades, either liquids or solids, and the average molecular weight ranges from 2,090 to 14,600. The poloxamers generally are white-colored, waxy, free-flowing granules or cast solids that are practically odorless and tasteless. The pH of a 2.5% w/v aqueous solution is in the range of 6.0 to 7.4. The poloxamers are stable and aqueous solutions are stable in the presence of acids, alkalis, and metal ions, but the aqueous solutions support mold growth. Poloxamer 407 (Pluronic F127) is generally available in powdered form. It either is odorless or may have a very mild odor. Poloxamer 407 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; 2012:334-386,1137,4340-4341.
2. Allen LV Jr. Standard operating procedure for performing physical quality assessment of ointments/creams/gels. IJPC. 1998;2:308-309.
3. Weller PJ. Propylene glycol. In: Rowe RC, Sheskey PJ, Quinn ME, eds. Handbook of Pharmaceutical Excipients. 6th ed. Washington, DC: American Pharmaceutical Association; 2009:592-594.
4. Sweetman SC, ed. Martindale: The Complete Drug Reference. 35th ed. London, England: Pharmaceutical Press; 2007:2142.
5. Fenton ME. Alcohol. In: Rowe RC, Sheskey PJ, Cook WG, Fenton ME, eds. Handbook of Pharmaceutical Excipients. 7th ed. Washington, DC: American Pharmaceutical Association; 2012:19-22.
6. Goskonda SR. Triethanolamine. In: Rowe RC, Sheskey PJ, Cook WG, Fenton ME, eds. Handbook of Pharmaceutical Excipients. 7th ed. Washington, DC: American Pharmaceutical Association; 2012:865-867.
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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