IN-VITRO SKIN PENETRATION OF MONOETHANOLAMINE AND DIETHANOLAMINE USING EXCISED SKIN FROM RATS, MICE, RABBITS, AND HUMANS

Monoethanolamine (MEA; CAS No. 141-43-5) and diethanolamine (DEA; CAS No. 111-42-2) are used in a number of cosmetic formulations. Therefore , dermal absorption is an important route of potential human exposure to these compounds. Because of this, the skin penetration characterist ics of these two alkanolamines were evaluated using an established in vitro technique. Full-thickness skin preparations from female CD rats, CD-1 mice, New Zealand White rabbits, and female mammoplasty patients were used. Using a dynamic, flow-through design, skin penetration app aratus, undiluted and aqueous solutions of [C-14]MEA and [C-14]DEA wer e applied to skin preparations from each species in an ''infinite dose '' manner at target doses of 4 mg/cm(2) and 20 mg/cm(2), respectively. The time course of C-14 penetration was then measured for 6 h. The re sults showed that undiluted MEA penetrated animal skin better than did undiluted DEA, but was approximately the same for human skin. For the aqueous applications of MEA and DEA, the penetration was similar to e ach species, except for rabbit skin, in which the permeability appeare d to be less for aqueous MEA than it was for aqueous DEA. Comparing un diluted and water diluted doses of each compound, the results showed t hat there was generally less skin penetration of the undiluted materia l than that for the diluted test substances. Therefore, the total abso rbed dose of MEA or DEA would be less for cutaneous exposures to undil uted MEA or DEA as compared to similar exposures to water solutions of either compound. A comparison of permeability constants among the spe cies tested suggests that the general rank order of skin penetration f or both chemicals, undiluted or diluted, as mouse > rabbit > rat > hum an skin. Therefore, the results from this in vitro study suggest that the potential percutaneous absorption of MEA or DEA would be less for humans than it would be for rats, rabbits, and mice.