COMPOUNDING HOTLINE

Author: Martin A. Erickson III, RPh

Q: How would you compound the following prescription: ketoprofen 5% organogel; dispense 30 g, using the following ingredients: ketoprofen, alcohol, lecithin, isopropyl, myristate, pluronic F-127, potassium sorbate, and purified water?

A: Nonsteroidal anti-inflammatory drugs (NSAIDs) commonly are used for the treatment of various neuropathies. Extemporaneously compounded preparations of these products typically contain a penetration enhancer to improve transdermal absorption of the medication. One such penetration enhancer is formed when isopropyl palmitate is used to dissolve lecithin (50:50). The preparation is available commercially as "lipoil."(It is often colloquially referred to as "motor oil" because of its color and consistency, but please avoid putting it in an engine crankcase.) This solvent-solute system is combined with the NSAID and frequently with other anesthetics or agents that affect other neurotransmitter sites in a gel or vanishing cream base.

One of the most common gel bases is poloxamer 407NF, trademarked as Pluronic F127NF powder and available commercially as Polox 10%, 20%, and 30%. The gel has inverse temperature- viscosity behavior: it is a liquid at refrigerated temperatures and becomes more viscous with increasing temperatures. This characteristic, combined with the protectant-humectant effect of a Tegaderm or OpSite overlay, provides a convenient vehicle for application of the lipoil combined with an active ingredient(s). The process of combining lipoil with the active ingredient should include a small amount of appropriate solvent to make a smooth paste with the comminuted powder(s), followed by high shear mixing (typically by passing the lipoilpoloxamer- active through an interconnected Luer-Lok to Luer- Lok syringe combination several times to achieve homogeneity).

The lipoil-poloxamer combination is known colloquially as "PLO" or "Pluronic-Lecithin-Organogel." Polox is preserved with potassium sorbate; lipoil has sorbic acid. Each of these products can be compounded extemporaneously. It is necessary to allow the poloxamer powder to remain in water in a refrigerated place for at least 24 hours. Lecithin:isopropyl palmitate 50:50 requires about the same amount of time to form a solution.

Supplies:

Beaker
Rubber spatula
Balance
Graduated cylinder

Procedure:

  1. Accurately weigh/measure each of the ingredients.
  2. Wet ketoprofen with a suitable solvent (ethoxydiglycol). Note: ketoprofen will not dissolve?make a smooth paste.
  3. Add 24 mL of lipoil to the above ingredients. Mix well.
  4. Add sufficient Polox gel to make 100 mL (density of the product ~1).
  5. Mix thoroughly.
  6. Package and label.

Notes:

Preserve Polox gel 20% in refrigerator for liquid consistency. Store finished preparation at room temperature.

E-mail your compounding questions to compounding@pharmacytimes.com

Mr. Erickson is director of professional affairs at Gallipot Inc.