Registration Dossier

Administrative data

Endpoint:
specific investigations: other studies
Type of information:
experimental study
Adequacy of study:
supporting study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
test procedure in accordance with generally accepted scientific standards and described in sufficient detail

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2010
Report Date:
2010

Materials and methods

Principles of method if other than guideline:
The potential of the test substance to sensitize the heart to a challenge of epinephrine injection was tested in Beagle dogs.
GLP compliance:
yes
Type of method:
in vivo
Endpoint addressed:
other: cardiac sensitization

Test material

Reference
Name:
Unnamed
Type:
Constituent
Test material form:
other: colourless gas
Details on test material:
- Analytical purity: 99.91413%

Test animals

Species:
dog
Strain:
Beagle
Sex:
male

Administration / exposure

Route of administration:
inhalation: gas
Vehicle:
air
Analytical verification of doses or concentrations:
yes
Duration of treatment / exposure:
air approximately 7 minutes
test substance approximately 10 minutes
Frequency of treatment:
one time exposure
Doses / concentrationsopen allclose all
Remarks:
Doses / Concentrations:
70000 ppm [7%]; 80000 ppm [8%]; 90000 ppm [9%]
Remarks:
Doses / Concentrations:
71477 ppm with SD of 3238; 82286 ppm with SD of 571; 90416 ppm with SD of 1179
No. of animals per sex per dose:
6 dogs exposed to 70000 ppm
1 dog exposed to 90000 ppm
1 dog exposed to 80000 ppm

Results and discussion

Details on results:
After exposure to 70000 ppm test substance, 2 of the 6 animals displayed continuous convulsions and excessive salivation and one animal had dilated pupils in both eyes.

After exposure to 90000 ppm test substance, intermittent and then continuous convulsions, excessive salivation, and dilated pupils of both eyes were noted for this animal. Exposure was terminated due to the severity of the observed clinical signs. No other animal was exposed to the test substance at 90000 ppm due to the adverse reaction shown.

After exposure to 80000 ppm test substance, intermittent and then continuous convulsions and excessive salivation were noted for this animal. Exposure was terminated due to the severity of the observed clinical signs. No other animal was exposed to the test substance at 80000 ppm due to the adverse clinical observations noted.

Due to the lack of PVCs with confluency, ventricular tachycardia, and fibrillation following the exposure of 70000 ppm test substance where animals were challenged with epinephrine, it was determined that exposure at this level did not result in cardiac sensitization. Because the epinephrine challenge was unable to be administered following exposure of 80000 and 90000 ppm, the potential for cardiac sensitization at these exposure levels was unable to be assessed.

Applicant's summary and conclusion

Conclusions:
The study and the conclusions which are drawn from it fulfil the quality criteria (validity, reliability, repeatability).
The no-observed-effect concentration (NOEC) for cardiac sensitization was 70000 ppm test substance.
Executive summary:

The objective of this study was to evaluate the cardiac sensitization potential during acute inhalation exposures by assessing the response to various concentrations of the test substance in Beagle dogs. Cardiac sensitization in this context refers to the potential for the test substance to increase the sensitivity of the heart to the pharmacological effects of epinephrine.

 

The test substance was administered to animals via a muzzle only inhalation apparatus as acute exposures (gas) at concentrations of 7%, 9%, and 8% (70000, 90000, and 80000 ppm [parts per million], respectively). One group of up to 6 male dogs per exposure level was used on this study with a minimum of 48 hours between exposure concentrations for each animal. Each dog served as its own control. Baseline responses to the epinephrine challenge doses were collected 5 days prior to exposure to the test substance. A predetermined challenge dose was established during this baseline prior to exposure for each individual animal. Escalating doses of epinephrine (2, 3, 4, 6, or 8 μg/kg) were administered as bolus intravenous (IV) injections (approximately 0.1 mL/kg delivered at a rate of approximately 0.1 mL/sec) until significant or dangerous cardiac effects were noted or the dose of 8 μg/kg elicited no effects, whichever was higher. For the 70000, 90000, and 80000 ppm groups, animals were administered the predetermined challenge dose of 8 μg/kg epinephrine via an appropriate vein beginning approximately 5 minutes prior to exposure to the test substance as well as approximately 5 minutes following exposure to the test substance. Two animals displayed an adverse reaction to the 70000 ppm dose and were replaced for subsequent exposures. The replacement animals were not exposed to the first exposure level of 70000 ppm. One animal displayed a severe adverse reaction to the second exposure level of 90000 ppm; no other animals were exposed to this level. The third exposure level of 80000 ppm was selected and was discontinued after a similar reaction (as that observed for the 90000 ppm exposure) was noted in the only animal to be exposed to this level. No further exposures were conducted. Following the final exposure, all animals were returned to the Test Facility's cardiovascular stock colony. Individual body weights were recorded on exposure days for calculation of epinephrine doses. Electrocardiographic (ECG) data were recorded continuously throughout the pre-exposure period, exposure to the test substance and throughout administration of the challenge epinephrine dose (up to approximately 17 minutes).

 

During the first exposure of 70000 ppm test substance, 2 of the 6 animals displayed continuous convulsions, excessive salivation, and/or dilated pupils following test substance exposure. During the next exposure of 90000 ppm test substance, 1 animal displayed continuous convulsions, excessive salivation, and dilated pupils during test substance exposure. No further animals were exposed to this concentration. During the last exposure of 80000 ppm test substance, the first animal exposed displayed continuous convulsions and excessive salivation during test substance exposure similar to that noted in the 90000 ppm exposure group. No further animals were exposed. All test substance exposures were terminated as soon as convulsions were apparent. There were no signs of cardiac sensitization after exposure to 70000 ppm. However, cardiac sensitization could not be evaluated following exposure to 80000 and 90000 ppm since the adverse clinical signs observed precluded the administration of epinephrine challenge.

 

Based on the results of this study, muzzle-only vapour exposure to 70000 ppm test substance in Beagle dogs followed by intravenous administration of 8 μg/kg epinephrine did not produce evidence of cardiac sensitization. Evaluation for cardiac sensitization was not possible in the 80000 and 90000 ppm test substance exposure groups due to adverse clinical signs that precluded the administration of epinephrine. Therefore, the no-observed-effect concentration (NOEC) for cardiac sensitization was 70000 ppm.