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Solubility: freely soluble in benzene, chloroform, ether, and petroleum spirit; sparingly soluble in cold ethanol (95%), more soluble in boiling ethanol (95%); practically insoluble in water.

Stability and Storage Conditions

Lanolin may gradually undergo autoxidation during storage. To inhibit this process, the inclusion of butylated hydroxyto- luene is permitted as an antioxidant. Exposure to excessive or prolonged heating may cause anhydrous lanolin to darken in color and develop a strong rancidlike odor. However, lanolin may be sterilized by dry heat at 1508C. Ophthalmic ointments containing lanolin may be sterilized by filtration or by exposure to gamma irradiation.(1)

Lanolin should be stored in a well-filled, well-closed container protected from light, in a cool, dry place. Normal storage life is 2 years.

Incompatibilities

Lanolin may contain prooxidants, which may affect the stability of certain active drugs.

400 Lanolin

Method of Manufacture

Lanolin is a naturally occurring wax-like material obtained from the wool of sheep, Ovis aries Linne´ (Fam. Bovidae).

Crude lanolin is saponified with a weak alkali and the resultant saponified fat emulsion is centrifuged to remove the aqueous phase. The aqueous phase contains a soap solution from which, on standing, a layer of partially purified lanolin separates. This material is then further refined by treatment with calcium chloride, followed by fusion with unslaked lime to dehydrate the lanolin. The lanolin is finally extracted with acetone and the solvent is removed by distillation.

Safety

Lanolin is widely used in cosmetics and a variety of topical pharmaceutical formulations.

Although generally regarded as a nontoxic and nonirritant material, lanolin and lanolin derivatives are associated with skin hypersensitivity reactions and the use of lanolin in subjects with known sensitivity should be avoided.(2,3) Other reports suggest that ‘sensitivity’ arises from false positives in patch testing.(4) However, skin hypersensitivity is relatively uncom- mon;(5) the incidence of hypersensitivity to lanolin in the general population is estimated to be around 5 per million.(6)

Sensitivity is thought to be associated with the content of free fatty alcohols present in lanolin products rather than the total alcohol content.(7) The safety of pesticide residues in lanolin products has also been of concern.(8,9) However, highly refined ‘hypoallergenic’ grades of lanolin and grades with low pesticide residues are commercially available.(10) See also Section 18.

Handling Precautions

Observe normal precautions appropriate to the circumstances and quantity of material handled.

Regulatory Status

Included in the FDA Inactive Ingredients Guide (ophthalmic, otic, topical, and vaginal preparations). Included in nonpar- enteral medicines licensed in the UK. Included in the Canadian List of Acceptable Non-medicinal Ingredients.

Related Substances

Cholesterol; hydrogenated lanolin; lanolin, hydrous; lanolin alcohols; modified lanolin.

See also Section 18.

Hydrogenated lanolin

Synonyms: adeps lanae hydrogenatus; hydrogenated wool fat.

Acid value: 41.0

Hydroxyl value: 140–180 Melting point: 45–558C Saponification value: 48.0

Water: 43.0%

Comments: some pharmacopeias, such as the PhEur 2005, contain a monograph for hydrogenated lanolin. This material is a mixture of higher aliphatic alcohols and sterols obtained from the direct, high-pressure, high-temperature hydrogenation of lanolin during which the esters and acids present are reduced to the corresponding alcohols. Hydro- genated lanolin may contain a suitable antioxidant; the

PhEur 2005 specifies not more than 200 ppm of butylated hydroxytoluene.

Modified lanolin

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.

Comments

Lanolin (the anhydrous material) may be confused in some instances with hydrous lanolin since the USP formerly contained monographs for ‘lanolin’ and ‘anhydrous lanolin’ in which the name ‘lanolin’ referred to the material containing 25–30% w/w of purified water. However, in the USP 28 the former lanolin monograph (hydrous lanolin) is deleted and the monograph for anhydrous lanolin is renamed ‘lanolin’.

Since lanolin is a natural product obtained from various geographical sources, its physical characteristics such as color, consistency, iodine value, saponification value, and hydroxyl value may vary for the products from different sources. Consequently, formulations containing lanolin from different sources may also have different physical properties.

A wide range of grades of lanolin are commercially available that have been refined to different extents in order to produce hypoallergenic grades or grades with low pesticide contents.

Many lanolin derivatives are also commercially available that have properties similar to those of the parent material and include: acetylated lanolin; ethoxylated or polyoxyl lanolin (water-soluble); hydrogenated lanolin; isopropyl lanolate; lanolin oil; lanolin wax; liquid lanolin; and water-soluble lanolin.

A specification for anhydrous lanolin is contained in the Food Chemicals Codex (FCC), where it is described as being used as a masticatory substance in chewing gum base. The EINECS number for lanolin is 232-348-6.

Specific References

Smith GG, Fonner DE, Griffin JC. New process for the manufacture of sterile ophthalmic ointments. Bull Parenter Drug Assoc 1975; 29: 18–25.

Anonymous. Lanolin allergy. Br Med J 1973; 2: 379–380.

Breit J, Bandmann H-J. Dermatitis from lanolin. Br J Dermatol

1973; 88: 414–416.

Kligman AM. The myth of lanolin allergy. Contact Dermatitis

1998; 39: 103–107.

Wakelin SH, Smith H, White IR, et al. A retrospective analysis of contact allergy to lanolin. Br J Dermatol 2001; 145(1): 28–31.

Clark EW. Estimation of the general incidence of specific lanolin allergy. J Soc Cosmet Chem 1975; 26: 323–335.

Clark EW, Cronin E, Wilkinson DS. Lanolin with reduced sensitizing potential: a preliminary note. Contact Dermatitis 1977; 3(2): 69–74.

Copeland CA, Raebel MA, Wagner SL. Pesticide residue in lanolin [letter]. J Am Med Assoc 1989; 261: 242.

Cade PH. Pesticide residue in lanolin [letter]. J Am Med Assoc

1989; 262: 613.

Steel I. Pure lanolin in treating compromised skin. Manuf Chem

1999; 70(9): 16–17.

Lanolin 401

General References

Barnett G. Lanolin and derivatives. Cosmet Toilet 1986; 101(3): 23–44. Osborne DW. Phase behavior characterization of ointments containing lanolin or a lanolin substitute. Drug Dev Ind Pharm 1993; 19:

1283–1302.

Smolinske SC. Handbook of Food, Drug, and Cosmetic Excipients.

Boca Raton, FL: CRC Press, 1992: 225–229.

PhEur: Alcoholes adipis lanae USPNF: Lanolin alcohols

Synonyms

Alcoholia lanae; alcolanum; Argowax; Hartolan; lanalcolum;

Ritawax; wool wax alcohols.

Chemical Name and CAS Registry Number

Lanolin alcohols [8027-33-6]

Empirical Formula and Molecular Weight

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.

Structural Formula

See Section 4.

Functional Category

Emulsifying agent; ointment base.

Applications in Pharmaceutical Formulation or Technology

Lanolin alcohols is used in topical pharmaceutical formulations and cosmetics as a hydrophobic vehicle with emollient proper- ties, 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 by the addition of 5% lanolin alcohols. Such emulsions do not crack upon the addition of citric, lactic, or tartaric acids.

Description

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

Pharmacopeial Specifications

See Table I.

Table I: Pharmacopeial specifications for lanolin alcohols.

Test PhEur 2005 USPNF 23

Identification + +

Characters + —

Melting range 5588C 5568C

Acidity and alkalinity + +

Clarity of solution + —

Loss on drying 40.5% 40.5%

Residue on ignition 40.1% 40.15%

Copper — 45 ppm

Acid value 42.0 42.0

Hydroxyl value 120–180 —

Peroxide value 415 —

Saponification value 412 412

Water absorption capacity + —

Butylated hydroxytoluene 4200 ppm —

Content of sterols (as cholesterol) 530.0% 530.0%

Typical Properties

Solubility: freely soluble in chloroform, dichloromethane, ether, and light petroleum; soluble 1 in 25 parts of boiling ethanol (95%); slightly soluble in ethanol (90%); practically insoluble in water.

Stability and Storage Conditions

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.

Incompatibilities

Incompatible with coal tar, ichthammol, phenol, and resorci- nol.

Method of Manufacture

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

Safety

Lanolin alcohols is widely used in cosmetics and topical pharmaceutical formulations and is generally regarded as a nontoxic material. However, lanolin alcohols may be irritant to the skin and hypersensitivity can occur in some individuals.(1)

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