Registration Dossier

Administrative data

Endpoint:
basic toxicokinetics
Type of information:
experimental study
Adequacy of study:
key study
Study period:
1991-09-18 to 1991-11-15
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Study follows GLP and internationally accepted test method guideline.

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
1991
Report Date:
1991

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
EPA OPP 85-1 (Metabolism and Pharmacokinetics)
Deviations:
no
GLP compliance:
yes

Test material

Reference
Name:
Unnamed
Type:
Constituent
Type:
Constituent
Details on test material:
NON-RADIOLABELLED MATERIAL
- Name of test material: nonradiolabeled DMH
- Physical state: white crystalline solid
- Analytical purity: >99.5%
- Lot/batch No.: 40-683, Ref F9431299.
- Stability under test conditions: considered stable under conditions of storage and use
- Storage condition of test material: stored in the refrigerator at 5 ºC

RADIOLABELLED MATERIAL
- Name of test material (as cited in study report): radiolabelled DMH or 14C-DMH
- Analytical purity: 99.55 %
- Lot/batch No.: 2742-080
- Specific activity: 26.3 mCi/mmol
- Locations of the label (if radiolabelling): 14C radiolabelling at carbon in position 5.
Radiolabelling:
yes
Remarks:
DMH radiolabelled with Carbon-14

Test animals

Species:
rat
Strain:
other: Charles River-CD rats (Crl:CD Br)
Sex:
male/female
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Charles River Breeding Laboratories, Kingston, NY
- Age at study initiation: 8 weeks
- Weight at study initiation: females: 166-184 g - males: 268-284 g
- Fasting period before study: 18 hours.
- Housing: individual hanging metal cages
- Individual metabolism cages: no
- Diet: ad libitum
- Water: ad libitum
- Acclimation period: 2-3 weeks

ENVIRONMENTAL CONDITIONS
- Temperature (°F): 63-71 °F
- Humidity (%): 25-72%
- Air changes (per hr): at least seven per hour
- Photoperiod (hrs dark / hrs light): 12 hours dark / 12 hours light

Administration / exposure

Route of administration:
other: Oral (gavage) and intraveneous (I.V.)
Vehicle:
other: Sterile water for injection USP for oral administration and saline for I.V. administration
Details on exposure:
PREPARATION OF DOSING SOLUTIONS:
Oral dose:
Radiolabeled dosing solutions were preapred by mixing a weighed amount of nonradiolabeled DMH with an appropriate amount of 14C-DMH in a glass vial. Sterile water for injection, USP was added to acheieve the desired final concentrations. The nonlabeled dosing solution used in the repeated low-dose oral experiment was prepared by mixing a weighed amount of non-radiolabeled DMH with an appropriate volume of sterile water. The dosing solution was made up once to dose on days 1 through 7 and a second time to dose on days 8 through 14.

IV dose:
The dosing solution preparation was identical to the oral dosing solution preparation except normal saline (0.9% Sodium Chloride) was used instead of sterile water.


VEHICLE
- Amount of vehicle: 5 mL of dosing solution per kg/bw for low dose (100 mg/kg) and 10 mL/kg in single oral high-dose group (1000 mg/kg). A dose volume of 2.5 mL/lg for IV administration was used.
- Lot/batch no: Sterile water (McGaw, Inc., Lot No. JDJ039A Exp. 7/91), 0.9% sodium chloride (Kendall McGaw, Lot #JDJ035A)



HOMOGENEITY AND STABILITY OF TEST MATERIAL:
Th radiolabeled purity of the 100 mg/kg and 1000 mg/kg oral dosing solutions was determined by HPLC to be greater than 99% on the day of dosing. The stability of 14C-DMH in corn oil was determined to be at least eight days by HPLC.
Duration and frequency of treatment / exposure:
Four experiments were conducted as part of the study which involved the administration of 14C-DMH at a single oral dose; at a repeated oral low dose; at a single oral high-dose; and at a single intravenous low-dose.
Rats in the repeat oral low-dose were administered non-radiolabelled DMH daily at a dose level of 100 mg/kg/day for days 1-7 and 80 mg/kg/day for days 8-14 by gavage prior to a single dose of 14C-labelled DMH.
All other regimens were provided as a single dose.
Doses / concentrations
Remarks:
Doses / Concentrations:
Single oral high dose: 1000 mg/kg
Single oral low dose: 100 mg/kg
Repeated oral low dose: 100 mg/kg (days 1-7) then 80 mg/kg (days 8-15) and radiolabelled material for the last dose only.
Intraveneous (I.V.): 100 mg/kg
No. of animals per sex per dose:
5/sex/group
Control animals:
no
Details on dosing and sampling:
PHARMACOKINETIC STUDY (Absorption, distribution, excretion)
- Tissues and body fluids sampled: urine, faeces, cage washes, blood, gastrointestinal tract (stomach, small intestine, large intestine, GI tract contents), bone, brain, fat, gonads (testes, seminal vesicles, prostate, ovaries, uterus); heart; kidneys; liver; lings; muscle; spleen; pancreas; skin; hair and residual carcass).

- Time and frequency of sampling:
Urine, faeces, and washings of urine/faeces separators were collected at the following intervals: 0-4 , 4-8, 8-12, 12-24, 24-36, 36-48, 48-72, 72-96, 96-120, 120-144 and 144-168 hours.
Blood, tissues and organs were harvested 7 days (168 h) after administration of 14C-DMH

METABOLITE CHARACTERISATION STUDIES
- Tissues and body fluids sampled: urine and faeces
- Time and frequency of sampling: samples were collected over the following time intervals: 0-6, 6-24, 24-48 and 48-72 hours.
- From how many animals: 5/sex
- Method type for identification: HPLC

Results and discussion

Preliminary studies:
Prior to undertaking this study, a preliminary study was undertaken to determine if 14C-CO2 would be evolved in the expired air following oral dose administration (BTC project number P01979). No significant amount of 14C-CO2 was evolved.

Toxicokinetic / pharmacokinetic studies

Details on absorption:

Test substance DMH was adsorbed completely and readily.
Details on distribution in tissues:
Tissue residues expressed as ppm 14C-DMH equivalents and percent of administered dose were very low and with the exception of the single oral high-dose group, were similar for all dosage regimens. The slightly higher tissue residue levels in a few tissues in the single oral high-dose group were considered to be a reflection of the higher dose administered to the animals in this group.
Only in hair and possibly fat, were residue levels above those found in plasma found with any regularity. The slightly higher residue levels in fat were not of the magnitude to suggest significant bioaccumulation. The residue levels in hair may indicate some preference for 14C-DMH to accumulate in this matrix or may be an artefact of trying to determine 14C residue levels in extremely small samples.
Details on excretion:
Regardless of dosing regimes, more than 90% of the dosed radioactivity in both male and female rats was excreted, unchanged, in the urine (90.50-96.25%) while less than 1.37% was excreted in the faeces. Most of the radioactivity recovered in the urine was excreted within the first 12 hours. Urinary half lives were superimposable, with values of 3.0-3.25h (males) and 2.4-2.8 h (females).

Metabolite characterisation studies

Metabolites identified:
no

Any other information on results incl. tables

Table 1: Mean total recovery of radioactivity expressed as a percentage of administered dose (%)

 

Males

Females

Dose level

Single oral low dose

Single oral high dose

Repeat oral low dose

Single IV low dose

Single oral low dose

Single oral high dose

Repeat oral low dose

Single IV low dose

Urine

 

94.18

 

90.50

 

95.68

 

95.34

 

93.34

 

93.37

 

96.25

 

93.80

 

Faeces

 

0.74

 

1.00

 

0.88

 

1.23

 

0.72

 

0.76

 

1.37

 

0.66

 

Carcass and tissue

0.03

 

0.16

 

0.01

 

0.12

 

0.03

 

0.01

 

0.11

 

0.04

 

Total14C

 

94.96

 

91.65

 

96.57

 

96.69

 

94.09

 

94.14

 

97.73

 

94.51

 

Applicant's summary and conclusion

Conclusions:
Interpretation of results (migrated information): no bioaccumulation potential based on study results
The data from the study demonstrated that 14C-DMH is well absorbed and rapidly and quantitatively excreted, unchanged, in the urine following oral or intravenous administration. There was no evidence for significant tissue accumulation.