Lanolin alcohols

Lanolin alcohols are obtained by saponification of purified wool grease, a mixture of high molecular esters that is recovered in wool (qv) scouring. Ethoxylation of purified lanolin alcohols yields a full series of lipophilic and hydrophilic nonionic emulsifiers whose largest use is in cosmetic preparations. Manufacturers include Amerchol, Croda, ICI, Henkel Corporation, Westbrook Lanolin, Witco, and Pulcra, SA. 

Cetyl acetate/acetylated lanolin alcohol 1 Emollient... 

Lanolin is a very complex mixture of esters, diesters, and hydroxy esters of high molecular weight lanolin alcohols and lanolin acids. Being a complex natural product, the method of refinement for lanolin is very important, as this determines the composition, properties, and quality of the purified lanolin.1-7 8 It is necessary, therefore, to bear in mind that not all refined lanolins are the same. The incredibly complex composition of lanolin also means that it cannot be synthesized.1... 

The purity of lanolin and standard tests have been described in the European Pharmacopoeia (EP), in The United States Pharmacopoeia (USP), and according to other national standards.13,14 Lanolin is a semisolid with a melting point of approximately 40 6°C and has a molecular weight in the range of 790 to 880 Da. Lanolin is a complex and variable mixture of mainly esters, diesters, hydroxy esters (87.0-93.5%, w/w),7 8 15 lanolin alcohols (6.0-12.5%, w/w), lanolin acids (<0.5%, w/w), and lanolin hydrocarbons (<1.0%, w/w). The latter are also called paraffins and petrolatum by the EP and USP, respectively.13,14 16-18 Approximately 40% of the esters are a-hydroxy esters. Due to the extremely complex nature of lanolin, the true number of different esters present is unknown. Barnett calculated the theoretical number of monoester combinations from random combinations of 69 aliphatic lanolin alcohols, 6 sterols, and 138 saturated lanolin acids to total 10,350.8 This is most probably an underestimate of the total number of esters, as dibasic acids and dihydric alcohols also occur naturally in lanolin.19 Further combinations of cyclic mono- and di-esters may be formed by dehydration and from inter- and intra-esterification due to heating during the manufacturing process.7 8... 

The analysis of lanolin has concentrated on the lanolin alcohols (the unsaponifiable fraction of lanolin) and lanolin acids produced by hydrolysis rather than the esters in lanolin itself.20 Lanolin alcohols belong to three major groups (1) 69 aliphatic alcohols from C12 to C36, (2) sterols (cholesterol and dihydrocholesterol), and (3) trimethyl sterols (lanesterol, dihydrolanesterol, agnosterol, and dihydroagenosterol).21 The latter have been incorrectly termed triterpenoids. The relative proportion of each group is 22% (w/w) aliphatic alcohols, 35% (w/w) sterols, and 38% (w/w) trimethyl sterols.8... 

The nature of the substance that is responsible for sensitization to lanolin is not clear, but it has a high affinity for the natural free alcohols.1 Clark has proposed that the incidence of adverse reactions can be virtually eliminated by reducing the level of lanolin alcohols to no more than 3% (w/w).1 Alternatively, the lanolin alcohols can be intensively purified to eliminate traces of the compounds which may cause sensitization 22... 

Stratum corneum lipids and lanolin share an important physical characteristic in that they can coexist as solids and liquids at physiological temperatures.33 A differential scanning calorimetry thermogram of lanolin is similar to that of stratum corneum lipids, showing two broad (heterogenous) phase transitions with midpoint melting temperatures at 21.9 and 38.3°C.16 The lower temperature peak may represent the transition from a liquid crystal to a gel phase, which has also been described for lanolin alcohols.34... 

Other physical methods of assessment of the stratum corneum, such as corneometry and micropro-filametry, demonstrate a statistically significant effect of lanolin.16 The parameters of skin roughness, Rz and Ra, determined by microprofilametry, can be reduced by 2 mg/cm2 lanolin alcohol or lanolin for at least 8 h after application.16... 

FIGURE 25.1 Lanolin alcohol (Eucerit , Beiersdorf AG, Hamburg, Germany) reduces skin roughness, as measured by microprofilometry. Lanolin alcohol (2 and 4%, w/w LA) in a water-in-oil cream containing petrolatum was applied twice daily to the volar aspect of the arm. (Adapted from Sauermann, G. and Schreiner, V., The Lanolin Book, Beiersdorf AG, Hamburg, 1999. With permission.)... 

Lanolin and lanolin alcohols are excellent emulsifiers, giving oil-in-water emulsions, and can be combined with additional emulsifiers such as cetearyl alcohol to improve stability.8 The ability of anhydrous lanolin and especially lanolin alcohols to form stable emulsions with up to 300% (w/w) of water distinguishes lanolin from petrolatum in its physical properties.1 The chemical compositions of lanolin and petrolatum are also very different, as petrolatum is composed completely of hydrocarbons.16 Lanolin alcohols and petrolatum can be combined to form cholesterized petrolatum, which also has the capacity to form emulsions. For example, a mixture of 65% (w/w) lanolin, 20% (w/w) water, and 15% (w/w) petrolatum can incorporate an equivalent weight of water without changing its consistency.15,52... 

The ability of lanolin alcohols to deliver active substances to the skin is partly due to their surface activity.15 Lanolin alcohols, which contain a high proportion of cholesterol, have a high surface activity and are able to reduce the interfacial tension of a mineral oil-water system from 52.5 to 5.0 dyn/cm.8,53 Even at low levels, cholesterol can reduce the interfacial tension of emulsions and dispersed systems.8,54... 

The extremely large number of lanolin derivatives has been reviewed by Barnett8 and Steel.16 Lanolin derivatives can be formed by acetylation, ethoxylation, propoxylation, alkoxylation, and isobutylation of hydroxy groups, as well as hydroxylation of the double bond in the sterol ester component. Hydrolysis of lanolin can also produce lanolin alcohols and lanolin acids, which like lanolin can be ethoxylated, acetylated, and hydoxylated. 

Sauermann, G. and Schreiner, V., The skin caring effects of topical products containing lanolin alcohols, in The Lanolin Book, Beiersdorf AG, Hamburg, 1999, p. 217. 

Iyer, B.V. and Vasavada, R.C., Evaluation of lanolin alcohol films andkinetics of release of triamcinolone acetonide release, J. Pharm. Sci., 68, 782, 1979. 

Topicort Desoximetasone, 0.25% White petrolatum USP, isopropyl myristate NF, lanolin alcohols NF, mineral oil USP, cetostearyl alcohol NF... 

Nonmedicated ointments are indicated for moderate to severe dry eye, especially with lagophthalmos, persistent inferior corneal stippling, or severe epithelial compromise. Esters of latty acids with long-chain alcohols, such as petrolatum, mineral oil, lanolin, and lanolin alcohols, serve as lubricants and create a lipid layer, retarding evaporation. Although these preparations (Table 14-2) melt at the temperature of the ocular tissue and disperse with the tear fluid, they appear to be retained longer than other ophthalmic vehicles. Because of their molecular... 

Lacri-Lube NP 55.5% White petrolamm 32% mineral oil 2% petrolatum/lanolin alcohol None... 

Lacri-Lube S.O.E 56.8% White petrolamm 42.5% mineral oil lanolin alcohols Chlorobutanol... 

Fatty alcohols Benzyl alcohol, butyl alcohol, cetostearyl alcohol, cetyl alcohol, cetyl esters wax, lanolin alcohols, octyldodecanol, oleyl alcohol, and stearyl alcohol... 

Lanolin alcohol Allergic contact eczema (SEDA-21, 501)... 

Comments some pharmacopeias, such as the USP 28, contain a monograph for modified lanolin. This material is lanolin that has been processed to reduce the contents of free lanolin alcohols and detergent and pesticide residues. It contains not more than 0.25% w/w of water. The USP 28 specifies that it may contain not more than 0.02% w/w of a suitable antioxidant. 

Cholesterol hydrogenated lanolin lanolin, hydrous lanolin alcohols modified lanolin. 

Lanolin alcohols is a crude mixture of steroidal and triterpene alcohols, including not less than 30% cholesterol, and 10-13% isocholesterol. The USPNF 23 permits the inclusion of up to 0.1% w/w of a suitable antioxidant, while the PhEur 2005 specifies that lanolin alcohols may contain up to 200 ppm of butylated hydroxytoluene as an antioxidant. 

Lanolin alcohols is used in topical pharmaceutical formulations and cosmetics as a hydrophobic vehicle with emollient properties, e.g., in preparations for dry skin and dry eyes. It is also used in the preparation of water-in-oil creams and ointments at concentrations as low as 2% w/w. The proportion of water that can be incorporated into petrolatum is increased threefold hy the addition of 5% lanolin alcohols. Such emulsions do not crack upon the addition of citric, lactic, or tartaric acids. 

Lanolin alcohols is a pale yellow to golden brown-colored solid that is plastic when warm hut hrittle when cold. It has a faint characteristic odor. See also Section 4. 

Lanolin alcohols may gradually undergo autoxidation during storage. Store in a well-closed, well-filled container, protected from light, in a cool, dry place. Normal storage life is approximately 2 years. 

Lanolin alcohols is prepared by the saponification of lanolin followed by separation of the fraction containing cholesterol and other alcohols. 

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