Percutaneous penetration and metabolism of 2-butoxyethanol. 2004

David J Lockley, and Douglas Howes, and Faith M Williams
Skin Toxicology Unit, Department of Environmental Medicine, University of Newcastle-upon-Tyne, NE2 4HH, UK. David.Lockley@Unilever.com

2-Butoxyethanol (2-BE) is widely used as an industrial solvent, which may result in human dermal exposure within the workplace. This study compares in vivo and in vitro skin absorption of 2-BE using similar application regimes and determines the potential of skin to metabolise this chemical prior to entering the systemic blood circulation. Following topical application of undiluted [1-14C] 2-BE to occluded rat skin in vivo, 28% of the dose was absorbed after 24 h. The major routes of excretion included the urine (19%), expiration as carbon dioxide (6%) and faeces (0.4%) whilst little of the dose remained in the carcass (1.3%). Free 2-BE (0.5%), butoxyacetic acid (8%), glucuronide conjugate (3%), sulphate conjugates (0.7%) and ethylene glycol (0.6%) were detected in urine. Permeation rates of 2-BE through unoccluded rat dermatomed skin (16%) were greater than rat whole skin (8%) whilst absorption through human dermatomed skin (4%) was lower than the rat. Absorption of undiluted 2-BE through occluded rat dermatomed skin in vitro (18%) most accurately predicted absorption through rat skin in vivo. However, 2-BE absorption (23%) was enhanced by application in methanol. Distribution analysis and microautoradiography demonstrated the lack of 2-BE accumulation within the skin in vitro or in vivo. This was reflected in the absence of first pass metabolism of 2-BE during percutaneous penetration through viable human or rat skin in vitro or rat skin in vivo, despite rat skin cytosol having the potential to metabolise 2-BE. In conclusion, the in vitro system provided a reasonable estimate of dermal absorption in vivo for the rat. Therefore, by extrapolation of the comparative in vitro data for human and rat skin in vitro, dermal absorption of 2-BE in man was about one-fifth of that in the rat. However, the rapid penetration through skin in vitro prevented local metabolism and systemic exposure after skin contact with 2-BE in vivo was likely to be to the parent compound. Thus, in vitro skin systems can be used to model dermal absorption of volatile glycol ethers, to predict how much compound enters the circulation and allows the toxicologist to evaluate the body burden of a chemical and potential systemic toxicity.

UI MeSH Term Description Entries
D008297 Male Males
D008658 Inactivation, Metabolic Reduction of pharmacologic activity or toxicity of a drug or other foreign substance by a living system, usually by enzymatic action. It includes those metabolic transformations that make the substance more soluble for faster renal excretion. Detoxication, Drug, Metabolic,Drug Detoxication, Metabolic,Metabolic Detoxication, Drug,Detoxification, Drug, Metabolic,Metabolic Detoxification, Drug,Metabolic Drug Inactivation,Detoxication, Drug Metabolic,Detoxication, Metabolic Drug,Detoxification, Drug Metabolic,Drug Inactivation, Metabolic,Drug Metabolic Detoxication,Drug Metabolic Detoxification,Inactivation, Metabolic Drug,Metabolic Drug Detoxication,Metabolic Inactivation
D002250 Carbon Radioisotopes Unstable isotopes of carbon that decay or disintegrate emitting radiation. C atoms with atomic weights 10, 11, and 14-16 are radioactive carbon isotopes. Radioisotopes, Carbon
D005026 Ethylene Glycols An ethylene compound with two hydroxy groups (-OH) located on adjacent carbons. They are viscous and colorless liquids. Some are used as anesthetics or hypnotics. However, the class is best known for their use as a coolant or antifreeze. Dihydroxyethanes,Ethanediols,Glycols, Ethylene
D005243 Feces Excrement from the INTESTINES, containing unabsorbed solids, waste products, secretions, and BACTERIA of the DIGESTIVE SYSTEM.
D006801 Humans Members of the species Homo sapiens. Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D000279 Administration, Cutaneous The application of suitable drug dosage forms to the skin for either local or systemic effects. Cutaneous Drug Administration,Dermal Drug Administration,Drug Administration, Dermal,Percutaneous Administration,Skin Drug Administration,Transcutaneous Administration,Transdermal Administration,Administration, Dermal,Administration, Transcutaneous,Administration, Transdermal,Cutaneous Administration,Cutaneous Administration, Drug,Dermal Administration,Drug Administration, Cutaneous,Skin Administration, Drug,Administration, Cutaneous Drug,Administration, Dermal Drug,Administration, Percutaneous,Administrations, Cutaneous,Administrations, Cutaneous Drug,Administrations, Dermal,Administrations, Dermal Drug,Administrations, Percutaneous,Administrations, Transcutaneous,Administrations, Transdermal,Cutaneous Administrations,Cutaneous Administrations, Drug,Cutaneous Drug Administrations,Dermal Administrations,Dermal Drug Administrations,Drug Administrations, Cutaneous,Drug Administrations, Dermal,Drug Skin Administrations,Percutaneous Administrations,Skin Administrations, Drug,Skin Drug Administrations,Transcutaneous Administrations,Transdermal Administrations
D000818 Animals Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA. Animal,Metazoa,Animalia
D012867 Skin The outer covering of the body that protects it from the environment. It is composed of the DERMIS and the EPIDERMIS.
D012869 Skin Absorption Uptake of substances through the SKIN. Absorption, Skin,Intracutaneous Absorption,Intradermal Absorption,Percutaneous Absorption,Transcutaneous Absorption,Transdermal Absorption,Absorption, Intracutaneous,Absorption, Intradermal,Absorption, Percutaneous,Absorption, Transcutaneous,Absorption, Transdermal,Absorptions, Intracutaneous,Absorptions, Intradermal,Absorptions, Percutaneous,Absorptions, Skin,Absorptions, Transcutaneous,Absorptions, Transdermal,Intracutaneous Absorptions,Intradermal Absorptions,Percutaneous Absorptions,Skin Absorptions,Transcutaneous Absorptions,Transdermal Absorptions

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