Q: I have a formulation that calls for “polyoxyl 40 hydrogenated castor oil.” What is that? Can I make a substitution?
A: This chemical is included in the National Formulary. It is a white-to-yellowish semisolid paste at 20°C; it melts at 30°C, has a faint but characteristic odor, and is nearly tasteless in aqueous solution. It results from the reaction of 1 mole of hydrogenated castor oil with ethylene oxide (40-45 moles). It is one of a series of chemicals that are complex mixtures of hydrophilic and hydrophobic components. This moiety is a commonly used emulsifier, mostly unaffected by the salts in hard water. One brand was found to prolong the dissolution time of digoxin tablets. Acute and chronic toxicity studies show this material to be essentially nontoxic and nonirritant, but some adverse reactions of unknown mechanism have been reported. It is stored in well-filled, airtight containers, where it is protected from light in cool, dry places. Synonyms include glycerol polyethyleneglycol oxystearate, hydrogenated castor oil POE-40, and PEG-40 hydrogenated castor oil. Brand names include Cremophor RH 40, Croduret 40, and Eumulgin HRE 40. The material is included in the FDA Inactive Ingredients Guide for use in intravenous injections and ophthalmic solutions. It also is found in a brand of cyclosporine capsules and can be used to solubilize other drugs. It has been used to solubilize vitamins and essential oils. Polyoxyl 40 hydrogenated castor oil 25% will solubilize vitamin A palmitate 88 mg/mL or vitamin A propionate 160 mg/mL. It can be used to emulsify fatty acids and alcohols. Hydroalcoholic preparations of this material produce foam, which can be reduced by adding polypropylene glycol 2000. It is almost tasteless when used in oral preparations.