US Pharm. 2018;43(3):42-43.
Method of Preparation: Calculate the quantity of each ingredient for the amount to be prepared. Accurately weigh or measure each ingredient. Dissolve the amitriptyline hydrochloride (HCl) in the alcohol. Mix the baclofen, ketamine HCl, and ketoprofen with the ethoxy diglycol to form a smooth paste; then incorporate the amitriptyline HCl solution and mix well. Incorporate the lecithin:isopropyl palmitate solution and mix well. Add the Pluronic F127 30% gel in portions with a shear mixing method to final volume. Package and label.
Use: This preparation has been used in the treatment of neuropathic pain conditions.
Packaging: Package in tight, light-resistant containers.1
Labeling: Keep out of reach of children. Use only as directed. For external use only.
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, texture-surface, texture-spatula spread, appearance, feel, rheologic properties, and physical observations.2
Discussion: Amitriptyline HCl (Elavil, C20H23N.HCl, MW 313.86) is a dibenzocycloheptene-derivative tricyclic antidepressant. It occurs as white or practically white, odorless or practically odorless, crystalline powder or small crystals. Amitriptyline HCl is freely soluble in water and alcohol.1,3,4
Baclofen (Lioresal, C10H12ClNO2, MW 213.66) occurs as a white to off-white, crystalline powder that is odorless or practically odorless. It is slightly soluble in water. Baclofen is used as a skeletal muscle relaxant.1,3
Ketamine HCl (C13H16ClNO.HCl, MW 274.2) is used as an anesthetic and analgesic. It occurs as a white, crystalline powder with a slight characteristic odor. Ketamine HCl is soluble 1 g in 4 mL of water, in 14 mL of alcohol, and in 60 mL of absolute alcohol.1,4
Ketoprofen (C16H14O3, MW 254.28) occurs as a white or almost white, odorless or almost odorless, crystalline powder. It is practically insoluble in water but is freely soluble in alcohol and ether.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 miscible with glycerin and water.5
Ethoxy diglycol (C6H14O3, CH2OHCH2OCH2CH2OC2H5, MW 134.20) also goes by the name of diethylene glycol monoethyl ether, diethylene glycol ethyl ether, Carbitol, and Transcutol. It occurs as a colorless liquid with a mild, pleasant odor. Ethoxy diglycol is hygroscopic and is miscible with water and with common organic solvents.6
Lecithin (egg lecithin, soybean lecithin, vegetable lecithin) derived from vegetable sources has a bland or nut-like taste and varies from brown to light yellow semiliquids or powders. It is practically insoluble in polar solvents and in cold vegetable and animal oils. Lecithin is soluble in aliphatic and aromatic hydrocarbons, mineral oil, and fatty acids.7
Isopropyl palmitate (C19H38O2, MW 298.51) is a colorless, mobile liquid with a very slight odor. It is soluble in castor oil, cottonseed oil, alcohol, and mineral oil. Isopropyl palmitate is insoluble in water, glycerin, and propylene glycol.8
Poloxamer 407 (Pluronic F127) is generally available in powdered form. It either is odorless or may have a very mild odor. It is freely soluble in water, alcohol, and isopropyl alcohol.9
1. U.S. Pharmacopeia/National Formulary [current revision]. Rockville, MD: U.S. Pharmacopeial Convention, Inc; February 2018.
2. Allen LV Jr. Standard operating procedure for performing physical quality assessment of ointments/creams/gels. IJPC. 1998;2:308-309.
3. McEvoy GK, ed. AHFS Drug Information 2016. Bethesda, MD: American Society of Health-System Pharmacists; 2016:1489-1493,2499-2500.
4. Brayfield A, ed. Martindale: The Complete Drug Reference. 38th ed. London, England: Pharmaceutical Press; 2014:79-80,401-107,1905-1906.
5. Quinn ME. Ethanol. In: Sheskey PJ, Cook WG, Cable CG, eds. Handbook of Pharmaceutical Excipients. 8th ed. London, England: Pharmaceutical Press; 2017:356-359.
6. Ash M, Ash I. Handbook of Pharmaceutical Additives. 3rd ed. Endicott, NY: Synapse Information Resources; 2007:604.
7. Shah HC, Singh KK. Lecithin. In: Sheskey PJ, Cook WG, Cable CG, eds. Handbook of Pharmaceutical Excipients. 8th ed. London, England: Pharmaceutical Press; 2017:538-541.
8. Quinn ME. Isopropyl palmitate. In: Sheskey PJ, Cook WG, Cable CG, eds. Handbook of Pharmaceutical Excipients. 8th ed. London, England: Pharmaceutical Press; 2017:497-498.
9. Pirjanian A, Alvarez-Nunez F. Poloxamer. In: Sheskey PJ, Cook WG, Cable CG, eds. Handbook of Pharmaceutical Excipients. 8th ed. London, England: Pharmaceutical Press; 2017:688-693.
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