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Basic toxicokinetics

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Administrative data

Endpoint:
basic toxicokinetics in vivo
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Well-documented publication which meets basic scientific principles

Data source

Reference
Reference Type:
publication
Title:
The pharmacokinetics of diethanolamine in Sprague-Dawley rats following intravenous administration
Author:
Mendrala AL, et al.
Year:
2001
Bibliographic source:
Food and Chemical Toxicology, 39, 931-939

Materials and methods

Objective of study:
toxicokinetics
Test guideline
Qualifier:
no guideline followed
Principles of method if other than guideline:
The pharmacokinetics of DEA at high and low dose was determined in rats administered 14C-labelled DEA via intravenous injection.
GLP compliance:
no

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
- Name of test material (as cited in study report): Diethanolamine
- Analytical purity: 99.3%
- Radiochemical purity: 97.4%
- Specific activity: 15 mCi/mmol
- Locations of the label (if radiolabelling): 14C (specific location not further specified)
Radiolabelling:
yes
Remarks:
14C

Test animals

Species:
rat
Strain:
Sprague-Dawley
Sex:
female
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Charles river laboratory (Kingston NY, USA)
- Age at study initiation: 11-weeks
- Weight at study initiation: 247-271
- Housing: singly
- Individual metabolism cages: yes
- Diet: lab diet PMI Nutrition international ad libitum
- Water: ad libitum
- Acclimation period: at least 7 days


ENVIRONMENTAL CONDITIONS
- Temperature (°C): 21-23
- Humidity (%): 40-70
- Photoperiod (hrs dark / hrs light): 12/12

Administration / exposure

Route of administration:
intravenous
Vehicle:
physiological saline
Duration and frequency of treatment / exposure:
single exposure
Doses / concentrations
Remarks:
Doses / Concentrations:
10 and 100 mg/kg bw
No. of animals per sex per dose:
10 females
Control animals:
no
Details on study design:
- Dose selection rationale: Doses were selected based on the finding that administration of 500 mg/kg via iv injection was lethal to rats (data not presented) while a dose of 100 mg/kg iv was well tolerated. The low dose level was selected as a dose level that was less than the lowest dose used in an oral subchronic toxicity study of DEA that caused minimal anemia and kidney histopathology in female rats (Melnick et al., 1994).
Details on dosing and sampling:
PHARMACOKINETIC STUDY (Distribution, excretion)
- Tissues and body fluids sampled: urine, faeces, blood, plasma, serum or other tissues (blood, liver, kidneys, heart, brain, stomach and samples of perirenal fat and skin); cage wash
- Time and frequency of sampling: urine/feces: 12 h intervals up to 96 hours; blood samples collected at: 5, 10, 15, 30 min and 1, 2, 4, 6, 12, 24, 36, 48, 60, 72 and 84 h post-dosing. Tissues, including liver, kidneys, heart, brain, stomach, peri-renal fat, and skin, were collected at 96 hours after administration.

Results and discussion

Toxicokinetic / pharmacokinetic studies

Details on absorption:
The tissues contained 69% of the administered radioactivity at the low dose and 57% at the high dose.
Details on distribution in tissues:
The largest portion (35%, low dose; 28%, high dose) was detected in the carcass. In the tissues examined, the highest levels were retained in liver (21 %, high dose; 17%, low dose) and kidneys (7%, high dose; 5%, low dose). Red blood cells also showed a tendency for a gradual accumulation of radioactivity between 6 and 96 hours after administration.
Details on excretion:
About 25% (low dose) and 36% (high dose) of the administered radioactivity was excreted in the urine as parent compound. The calculated clearance of DEA from blood was 84 ml/h/kg bw for the low dose and 242 ml/h/kg bw for the high dose. The dose dependency of the distribution and elimination of DEA was considered as an indication for saturation of bioaccumulation at the higher dose level of 100 mg/kg bw.

Metabolite characterisation studies

Metabolites identified:
not measured

Any other information on results incl. tables

Results summary:

Tissues, including liver, kidneys, heart, brain, stomach, perirenal fat, and skin contained 69% of the administered radioactivity at the low dose and 57% at the high dose 96h after dosing.

The largest portion (35%, low dose; 28%, high dose) was detected in the carcass. In the tissues examined, the highest levels were retained in liver (17%, high dose; 21%, low dose) and kidneys (5%, high dose; 7%, low dose).

Red blood cells also showed a tendency for a gradual accumulation of radioactivity between 6 and 96 hours after administration.

About 25% (low dose) and 36% (high dose) of the administered radioactivity was excreted in the urine as the parent compound.

The calculated clearance of DEA from blood was 84 ml/h per kilogram bw for the low dose and 242 ml/h per kg bw for the high dose.


Detailed results:
The mean recoveries of administered radioactivity were 95-96% for both the 10 and 100 mg/ kg dose levels. At 96 h post-dosing, an average of approximately 69 and 57% of the radioactivity administered was recovered in the tissues for the 10 and 100 mg/kg dose levels, respectively. The majority of this radioactivity was associated with the carcass (35 and 28% for the 10 and 100 mg/kg dose levels, respectively).

The liver and the kidneys accounted for the next highest percentage of the administered dose. About 5% of the administered dose was associated with the skin at both dose levels and less than 1% of the administered dose was associated with brain, fat, heart and stomach at either dose level.

The livers contained the highest concentrations of radioactivity at both dose levels, followed by the kidneys containing slightly lower concentrations compared to the livers. Concentrations of radioactivity found in the kidneys and liver were approximately 5- to 20-fold higher than the concentrations found in all other tissues measured.

The major route of excretion of radioactivity was via the urine with an average of about 25 and 36% of the administered dose excreted in the urine by 96 h post dosing for the 10 and 100 mg/kg dose levels, respectively. Urinary excretion of radioactivity was rapid at the high dose level with approximately 23% of the administered dose recovered in the first 12 h post-dosing. At the 10 mg/kg dose level, only 8.5% of the administered radioactivity was excreted in the first 12 h post-dosing. There was a faster elimination of radioactivity via the urine following the 100 mg/kg dose level when compared to the 10 mg/kg dose level.

A rapid initial urinary elimination phase was observed, followed by slow elimination of radioactivity via the urine through 96 h post-dosing. The initial urinary elimination half-lives were estimated to be 3.5 and 2.4 h for the 10 and 100 mg/kg doses, respectively.

The peak concentrations of plasma 14C-DEA-derived radioactivity at both dose levels were found at 5 min post-dosing and elimination of the radioactivity from the plasma occurred in a bi-exponential manner.

The peak concentrations of RBC 14C-DEA-derived radioactivity at both dose levels were also found at 5 min post-dosing, although the concentrations of radioactivity in the RBC were approximately 2-fold higher than plasma concentrations through 6 h post-dosing.

At both dose levels, the concentrations of radioactivity in the RBC initially declined rapidly, but starting at 6-12 h post-dosing the RBC gradually accumulated radioactivity. The concentration of radioactivity in both plasma and RBC was roughly proportional across dose levels at all times post-dosing. The concentrations of both 14C in plasma and DEA in blood decreased in a bi-exponential manner and were well described by a two-compartment pharmacokinetic model.

Clearance of radioactivity from plasma was calculated to be approximately 50 ml/h/kg at the low dose, increasing almost 2-fold to approximately 93 ml/h/kg at the high dose. Radioactivity remained detectable at 96 h post-dosing in the plasma of both the low and high dose groups, at which time the animals were euthanized.

The plasma area under curves (AUC) were not proportional to dose. A 5-fold increase in plasma AUC across the dose groups contrasted with the 10-fold increase in dose. Half-lives of approximately 10 min for the alpha-elimination (initial) phase for the low dose increases slightly to approximately 16 min for the high dose c-elimination phase. A slower beta-elimination (terminal) phase of 14C elimination became apparent after approximately 4 h. The terminal half-life of beta-elimination was estimated as 270 h for the low dose and faster at 113 h for the high dose.

The clearance of DEA from blood was calculated to be approximately 84 ml/h/kg at the low dose, increasing almost threefold to approximately 242 ml/h/kg at the high dose. The blood-DEA AUCs were not proportional to dose. A 3.5-fold increase in plasma AUC across the dose groups contrasted with the 10-fold increase in dose.

For blood DEA, half-lives of approximately 6 min for the alpha-elimination phase for the low dose increased to approximately 35 min for the high dose. A slower beta-elimination phase of 14C elimination became apparent after approximately 4 h.

The urinary concentrations of DEA were 18.9, 6.35, 1.92 and 2.14 µg/g for the 0-12, 36-48, 60-72 and 84-96 h collection intervals, respectively, at the 10 mg/kg dose level. A disproportionate increase in the urinary excretion of DEA relative to the increase in dose was observed at 0-12 h post dosing for the 100 mg/kg dose level where the urinary concentrations of DEA were determined 40-fold higher than at 10 mg/kg. At subsequent intervals at the 100 mg/kg dose level, the urinary concentrations of DEA were determined to be 43.2, 18.8 and 19.9 pg/g for the 36-48h, 60-72h and 84-96 h collection intervals, respectively, which were roughly proportional to the urinary concentrations found at the lower dose level. Based an the concentration of radioactivity in the pooled urine samples the DEA excreted in the urine at both 10 and 100 mg/kg comprised a majority of the urinary radioactivity ranging from 49 to 83% at the intervals analyzed.


Distribution of radioactivity recovered after iv administration of 14C-DEA

Organ

% administered

µg equivalents DEA/g tissue

10 mg/kg

100 mg/kg

10 mg/kg

100 mg/kg

Urine and cage rinse

25.05 ±3.35

36.27 ±1.18

Faeces

1.17  ± 0.19

1.50  ± 0.43

Final cage wash

0.56  ± 0.36

0.34  ± 024

Tissues

69.72  ± 2.93

56.72  ± 1.65

Brain

0.41 ± 0.06

    0.38  ± 0.01

1.92 ± 0.23

19.17 ± 1.86

Carcass

34.55  ± 4.29

28.24  ± 1.37

1.52 ± 0.18

13.60 ± 1.01

Fat

0.04 ±0.02

0.02 ±0.02

1.18 ± 0.36

9.27 ± 2.94

Heart

0.23 ±0.05

0.21 ±0.03

2.03 ± 0.27

22.29 ± 3.23

Kidneys

7.18 ±1.14

4.87 ±0.80

26.20 ± 4.22

199.16 ± 25.17

Liver

20.89 ±2.77

17.14 ±2.10

15.19 ± 2.70

136.66 ± 18.35

Stomach

0.80 ±0.12

0.67 ±0.08

2.65 ± 0.35

23.11 ± 8.92

Skin

5.12 ±0.63

5.18 ±0.65

2.49 ± 0.14

24.43 ± 1.65

Total
recovery

96.00 ±3.41

94.83 ±0.92

 %, values represent mean ± SD for 5 rats.


Radioactivity excreted in the urine after iv administration of 14C-DEA

Time (h)

% Administration radioactivity

10 mg/kg

100 mg/kg

0-12

8.50 ± 0.77

23.09 ± 1.68

12-24

3.16 ± 0.58

2.69 ± 0.61

24-36

1.27 ± 0.74

0.85 ± 0.14

36-48

2.77 ± 0.90

2.4 ± 0.44

48-60

2.45 ± 1.11

1.6 ± 0.38

60-72

2.61 ± 0.91

2.12 ± 0.43

72-84

1.81 ± 0.31

1.41 ± 0.42

84-96

2.48 ± 0.88

2.12 ± 0.16

total

25.05 ± 3.35

36.27 ± 1.18

Values represent mean ± SD for 5 rats.

Applicant's summary and conclusion