1,3,5-trioxane

Basic toxicokinetics

Administrative data

Endpoint:

basic toxicokinetics

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Acceptable, well-documented publication which meets basic scientific principles

Data source

Reference

Reference Type:

publication

Title:

The disposition and metabolism of 1,3,5-[U-14C]trioxane in male Wistar albino rats.

Author:

Ligocka D, Sapota A, Jakubowski M

Year:

1998

Bibliographic source:

Arch Toxicol 72: 303-308

Materials and methods

Objective of study:

distribution

excretion

metabolism

Test guideline

Test guideline 1

Qualifier:

no guideline available

Test guideline 2

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 417 (Toxicokinetics)

Version / remarks:

(adopted 1984)

Deviations:

yes

Remarks:

(few methodic deviations such as reduced acclimatisation period, however without conspicuous relevance for the validity of the results)

GLP compliance:

no

Test material

Test material information

Constituent 1

Reference substance name:

1,3,5-trioxane

EC Number:

203-812-5

EC Name:

1,3,5-trioxane

Cas Number:

110-88-3

Molecular formula:

C3H6O3

IUPAC Name:

1,3,5-trioxane

Details on test material:

(1) 1,3,5-Trioxane, unlabelled
freshly purified by sublimation
No further data
(2) 14C-labelled Trioxane
chromatographically pure
Specific activity of 3.6 MBq/mmol

Radiolabelling:

yes

Remarks:

14C-labelling

Test animals

Species:

rat

Strain:

Wistar

Sex:

male

Details on test animals or test system and environmental conditions:

Designation: 84 male Wistar albino rats
Source: no data
Mean body weight at test initiation: ca. 220 g +/-10%
Maintenance: individually into glass metabolism cages
Acclimatisation: for 48 h

Administration / exposure

Route of administration:

intraperitoneal

Vehicle:

physiological saline

Details on exposure:

- The 84 animals were placed into two groups; the animals of the first and the second group were administered i.p. 40 mg/kg and 400 mg/kg bw of 14C-trioxane, respectively.
- The 14C-trioxane solution with a specific activity of 870 kBq/ml, was prepared directly before administration by adding an appropriate amount of trioxane without an isotopic marker dissolved in 0.9% NaCl; each animal received 1 ml of the solution;
- Immediately after administration, the rats were placed in individual metabolism cages, which enabled the collection of separate urine and faeces samples;
- The expired air was extracted from the cages with the use of a water pump through three washers, fixed one after another and containing 25 ml of water and 25 ml of ethanolamine. The washers were exchanged every hour during the first 14 h for up to 24 h;
- Blood samples were collected from the tail veins of 12 rats using calibrated, heparinized capillaries at 0-48 h following administration of the compound; 30 µl of blood was collected each time. After centrifugation the value of the haematocrit was checked. The capillary was cut off at the division line; plasma and red blood cells were put separately into scintillation vials. In order to count 14C content in the whole blood, ca. 7 ml of blood/100 g bw was acceptable.
- The animals were sacrificed at specified time intervals; the liver, kidneys, lung, brain, spleen, sciatic nerve and a section of fat tissue from the abdomen were examined.

Duration and frequency of treatment / exposure:

Single application by i.p. injection

Doses / concentrations

Remarks:

Doses / Concentrations:
40, 400 mg/kg bw

No. of animals per sex per dose / concentration:

42 animals/group

Control animals:

no

Results and discussion

Toxicokinetic / pharmacokinetic studies

Details on distribution in tissues:

- When administered at a dose of 40 mg/kg bw, in most of the examined tissues the peak radioactivity was detected 2 h after administration. The highest 14C concentration was noted in the liver, while the lowest was in fat tissue, sciatic nerve and brain.
- When administered at a dose of 400 mg/kg bw, in most of the examined tissues the peak radioactivity was detected 2 h after administration. The highest 14C concentration was noted in plasma, liver and kidney; the lowest concentration was found in fat tissue and brain.
- In tissues, a rapid decline of radioactivity with time could be noted in all tissues. The total amount of the absorbed 14C in the tissues and blood after 72 h following application was not significant and constituted about 1.2% of the initial dose for animals treated with 40 mg/kg bw and 1.5% of the initial dose for animals treated with 400 mg/kg bw.

Details on excretion:

- The exhaled air proved to be the main route of 14C elimination, mainly as 14CO2; this was followed to a lesser extend by urine and faeces.
- When administered at a dose of 40 mg/kg bw,14C was found only in the ethanolamine trapping solution, which indicates that 14CO2 was in fact the only excreted compound; the maximum excretion took place 2 h after administration. The total amount of CO2 expired during the first 24 hours following treatment was 86.6 +/- 3.4% of initial dose. Elimination of trioxane by exhalation during the first 12 hr following the administration of 40 mg/kg bw was rapid with a half-life of 3.5 h. Total recovery in urine was about 3% over 72 hours following treatment, with 2.2% already recovered during the first 24 hours; radioactivity in urine was related to parent compound, as showed by gas chromatography and mass spectrometry (GC-MS). Recovery of radioactivity in faeces did not exceed 0.5%. Total excretion was about 89.5%.
- When administered at a dose of 400 mg/kg bw, trioxane also was mainly eliminated via the expired air; however, the expired radioactivity was related to CO2 at 69.71 +/- 2.35% of initial dose, whereas ca. 8% of the initial dose was identified as unchanged parent compound in exhaled air (24 hours after application). The maximum of excretion was reached after 12 hours following application. About 1.3 % of the 14C was excreted in the urine as unchanged trioxane. Recovery in faeces was 1.3%, however this was probably due to contamination of the faeces samples with urine. Total excretion was about 80%.
- On the basis of the amount of expired 14CO2, a Vmax of 9.32 kg/h and a Km of 17.08 mg/kg were calculated.
- With regards to trioxane elimination from blood plasma for the lower dose, a biphasic process was observed, with half-lives of 4.5 and 72 h. When the higher dose of trioxane was administered the efficiency of 14C binding to the erythrocytes was found to be 10 times higher than the respective value for blood plasma.

Metabolite characterisation studies

Metabolites identified:

not measured

Details on metabolites:

The data obtained confirmed the assumed pattern of metabolic transformation, according to which 1,3,5-trioxane undergoes enzymatic transformation to formaldehyde, with carbon dioxide and water being the final products.

Any other information on results incl. tables

Table 1: Elimination of 14C after single administration of 1,3,5 -[U-14C]trioxane to rats. Values are presented in % of initial dose +/-SEM for n=6 rats.

dose [mg/kg]	expired air 0-24h	urine 0-24h	urine 24-48h	urine 48-72h	faeces 0-72h	total
40	86.7 +/-3.4 (CO2)	2.2 +/-0.1	0.38+/-0.2	0.26+/-0.1	0.5+/-0.1	89.5
400	69.7 +/-2.4 (CO2) 8 +/-0.2 (triox.)	0.97+/-0.1	0.21+/-0.04	0.11+/-0.08	1.3+/-0.1	80.5