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Toxicological information

Basic toxicokinetics

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Administrative data

basic toxicokinetics in vivo
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: basic data given

Data source

Reference Type:
Distribution and Metabolism of Topically Applied Ethanolamine
Klain, GJ; Reifenrath, WG; Black, KE.
Bibliographic source:
Fundamental and Applied Toxicology 5, S127-S133

Materials and methods

Objective of study:
Test guideline
no guideline followed
Principles of method if other than guideline:
The absorption, distribution and metabolism of topical [14C]-ethanolamine was studied in vivo, using athymic nude mice and human skin grafted onto athymic nude mice.
GLP compliance:

Test material

Constituent 1
Chemical structure
Reference substance name:
EC Number:
EC Name:
Cas Number:
Molecular formula:
Details on test material:
Name if test material: ethanolamine
Analytical purity: 97%
Radiochemical purity: >95%
Specific activity: 4 µCi/mmol
Location of the label: [1,2-14C]ethanolamine HCl

Test animals

other: nude
Details on test animals or test system and environmental conditions:
Source: Harlan Industries (IND, US)
Weight at initiation: 30 g

Mice were grafted with human skin (0.5mm thickness), obtained by dermatome from consenting volunteers following breast surgery.
Grafting was performed using procedure described in Black and Jederberg (Athymic nude mice and human skin grafting. In Models in Dermatology
(L. Maibach, ed.), Vol 1, pp. 228-239. Karger, Basel.1985).

Administration / exposure

Route of administration:
Details on exposure:
Ethanolamine was applied with a microliter syringe at a chemical dose of 4.0 µg and a radioactive dose of 3.6 µCi to a 1.45-cm2 graft area, using ethanol (10 µl) as a vehicle.

The same dose was applied to a similar circular area outlined on the flank skin of nongrafted mice or administered intraperitoneally to another group of nongrafted mice. The mice were immediately placed in all-glass metabolism cages, and expired 14CO2 was collected for 24 hr in 2% aqueous NaOH. Radioactivity in the NaOH solution was periodically determined. Urine was collected for 24 hr in 0.5% HCl.
Duration and frequency of treatment / exposure:
24 h, single exposure
Doses / concentrations
Doses / Concentrations:
chemical dose of 4.0 µg and a radioactive dose of 3.6 µCi to a 1.45-cm2 graft area, using ethanol (10 µl) as a vehicle
No. of animals per sex per dose / concentration:
5 animals in total per treatment group
Control animals:
Positive control reference chemical:
(1) same dose applied to a similar circular area outlined on the flank skin of non-grafted mice
(2) same dose administered intraperitoneally to another group of non-grafted mice.
Details on study design:
Pharmacokinetic study (Adsorption, distribution, excretion).
- Tissues and body fluids sampled; exhaled air; urine; faeces; liver; kidney; lung; brain; heart; muscle.

Results and discussion

Toxicokinetic / pharmacokinetic studies

Details on absorption:
The results indicated that topical applied 2-aminoethanol penetrates the skin and is widely distributed in the body, radioactivity being detected in all the tissues and organs examined. Percutaneous penetration of the skin appears however to be relatively slowly, demonstrated by a marked time lag in the initial appearance of labelled carbon dioxide between topical and intraperitoneal treatment. Radioactivity in expired CO2 was detected 5 min after an intraperitonealadministration of 2-aminoethanol, while no radioactivity in expired air was detected during the first 20 min post-topical application.
Details on distribution in tissues:
24% of the applied radioactive dose was recoved in the liver. Further recovery of the administered radioactive dose was at skin administration site (24.3%), as exhaled CO2(over 18%), in urine (4.6%), in kidneys (2.5%) and in feces (1.8%). Lungs, brain, and the heart contained 0.55, 0.27, and 0.15% of the dose, respectively.
Transfer into organs
Test no.:
Transfer type:
blood/brain barrier
distinct transfer
Details on excretion:
Over 18% of the topical radioactive dose was oxidised to [14C]CO2 and 4.6% was excreted in the urine and 1.8% in faeces over 24h.

Metabolite characterisation studies

Metabolites identified:
Details on metabolites:
The substance is readily metabolized in the skin as well as in other organs and tissues in the mouse. Liver is a major site for metabolism of 2-aminoethanol. Extensive metabolization was indicated by appearance of labelled carbon dioxide in skin and hepatic amino acids, proteins and incorporation into phospholipids, and by recovery of over 18% of radioactive dose as [14]-CO2. Urea, glycine, serine, choline, and uric acid were the urinary metabolites of 2-aminoethanol.

Any other information on results incl. tables

Results details:

Distribution of radioactivity in grafted and ungrafted athymic nude mice 24 h after topical application of ethanolamine (n=5)


Human skin grafted nude mouse

ungrafted nude mouse


0.15 ± 0.02

0.13 ± 0.01


0.27 ± 0.07

0.25 ± 0.04


0.55 ± 0.09

0.63 ± 0.03


2.53 ± 0.15

2.24 ± 0.19


24.30 ± 3.82

25.80 ± 4.1

muscle gastroeneminus

398 ± 49*

427 ± 39*

skin application site

18.4 ± 2.7

12.1 ± 0.93

skin untreated

201 ± 34*

275 ± 24


4.60 ± 0.57

5.20 ± 0.72


1.82 ± 0.21

0.98 ± 0.64

cotton swabs

2.85 ± 0.36

3.28 ± 0.25

data represent means ± SE percentage of administered dose; * dpm/mg tissue

Radioactivity in proteins and amino acids isolated from the liver, human skin grafts and mouse skin after topical application




Mouse skin**

Protein (dpm/mg)

958, 983

241, 199

119, 157

Amino acids***


47.1, 44.6

38.6, 39.4

40.2, 42.8


22.2, 18.3

traces only

traces only

Glutamic acid

10.2, 8.1


15.8, 14.5


2.7, 1.9

6.3, 6.4

5.9, 6.5

Aspartic acid

1.4, 1.1

3.1, 4.1

3.8, 3.2


13.6, 14.9

34.2, 34.9

31.9, 33.1

* individual values from 2 grafted mice

** individual values from 2 grafted mice and two ungrafted mice

*** percentage of radioactivity applied to chromatographic columns

Applicant's summary and conclusion

Interpretation of results (migrated information): no bioaccumulation potential based on study results
Topical administration of ethanolamine penetrates the skin (to similar extents in mice and human sin grafted mice),and is readily metabolised in the skin as well as in other organs and tissues of the mouse. Percutaneous penetration is relatively slow.
Metabolism is most extensive in the liver, where ethanolamine is converted into amino acids serine and choline.