Trifluoroiodomethane

Specific investigations: other studies

Link to relevant study record(s)

Reference

Endpoint:

specific investigations: other studies

Remarks:

Acute cardiac sensitization

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

17 Feb 2006 to 23 Mar 2006

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

test procedure in accordance with generally accepted scientific standards and described in sufficient detail

Qualifier:

no guideline available

Principles of method if other than guideline:

The substance was administered via muzzle-only inhalation exposure (vapor) as acute exposures at concentrations of 2.0%, 3.5%, 5.0% and 7.5% (20,000, 35,000, 50,000 and 75,000 ppm, respectively). One group of 6 male dogs was used on this study, which received the 4 doses with intervals of at least 48 hours. Each dog served as its own control. For the 2.0%, 3.5% and 5.0% groups, animals were administered a predetermined dose of epinephrine as a bolus injection via a cephalic vein approximately 5 minutes prior to exposure to the test article. Five minutes after exposure to the test article began, the animals were administered a challenge dose of epinephrine. For the 7.5% group, exposure to the test article was initiated and then 3 doses of epinephrine were administered 5 minutes apart. Following the final exposure, all dogs were returned to stock. All animals were observed twice daily for mortality and moribundity. Clinical examinations were performed prior to initiation of each exposure, continually during the exposure and immediately following each exposure period. Detailed physical examinations were performed and body weights were collected prior to the first day of exposures and at the completion of all exposures. Electrocardiographic data were recorded continuously throughout the pre-exposure epinephrine dosing, exposure to the test gas and for 5 minutes following administration of the challenge epinephrine dose (total of approximately 17 minutes).

GLP compliance:

yes

Type of method:

in vivo

Endpoint addressed:

other: Acute cardiac sensitization

Specific details on test material used for the study:

SOURCE OF TEST MATERIAL
- Identity: Proprietary Refrigerant Blend containing 29.8 to 31.3% CF3I
- Source and lot/batch No.of test material: Honeywell, Buffalo, New York
- Physical appearance: clear gas
- Storage condition of test material: Room temperature

Species:

dog

Strain:

Beagle

Sex:

male

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: WIL Research Laboratories, LLC stock dog colony
- Age at study initiation: 6.5 to 9 months old at the initiation of exposure.
- Weight at study initiation: 7.9 to 10.3 kg
- Housing: The animals were housed individually in clean, stainless steel cages elevated above stainless steel cage pans that were cleaned daily. Animals were maintained in accordance with the Guide for the Care and Use of Laboratory Animals (National Research Council, 1996). The animals were allowed regular opportunity for exercise and social interaction in accordance with the standard operating procedures at WIL Research Laboratories, LLC, and the Animal Welfare Act (9 CFR Part 3).
- Diet: Approximately 400 g of PMI Nutrition International, LLC, Certified Canine LabDiet 5007, was offered 1 to 2 hours per day. Feed was withheld during exposure periods.
- Water: Reverse osmosis-treated (on-site) drinking water, delivered by an automatic watering system, was provided ad libitum throughout the study period. Water was withheld during exposure periods.
- Acclimation period: Animals considered suitable for the study were housed for an appropriate acclimation/pretest period. During this period, each animal was observed twice daily for mortality and changes in general appearance or behavior. Fecal samples were collected prior to the initiation of dose administration and checked for parasites; none were present. Individual body weights were recorded and detailed physical examinations were performed periodically during the pretest period. Food consumption and electrocardiographic data were also recorded for pretest animals prior to the initiation of dose administration. During the acclimation period, each dog was acclimated to exposure/restraint for several 10 to 20 minute periods. At least 10 acclimation sessions/dog were conducted.
- All animals were immunized prior to arrival at WIL Research Laboratories, LLC. The immunizations included rabies, Bordetella, distemper, adenovirus type 2, Leptospira spp, parvovirus, parainfluenza and oral papilloma virus.

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 21.2 to 21.7
- Humidity (%): 32.8 to 52.5
- Air changes (per hr): 10
- Photoperiod (hrs dark / hrs light): 12/12

Route of administration:

inhalation: vapour

Vehicle:

air

Details on exposure:

GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: Each animal was exposed individually using a muzzle-only exposure apparatus operated under dynamic conditions to supply the target concentration of the test article vapor and a minimum oxygen content of 19%. The mask used in the muzzle-only exposure system is a WIL-designed and manufactured, dual-port mask constructed of Neoprene®, nylon straps and “hook-and-loop” fastening material. Exposures were conducted using a muzzle-only system consisting of a mask connected to 3-way valve connected to a gas bag containing the appropriate test article mixture.
- Method of holding animals in test chamber: Each dog was comfortably restrained using a canvas sling with the appropriate ECG (limb) leads attached.
- Source and rate of air: The control atmosphere (the first 7 minutes of each exposure) was filtered air supplied from an in-house source.
- Method of conditioning air: Oxygen was added to each gas bag as needed to maintain oxygen content above 19%.

TEST ATMOSPHERE
- Prior to each exposure, samples were analyzed from each bag using a gas chromatographic method to assure that the atmosphere was at the target concentration.

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

- Prior to each exposure, samples were analyzed from each bag using a gas chromatographic method to assure that the atmosphere was at the target concentration.

Duration of treatment / exposure:

10 minutes for the 2, 3.5 and 5% dose-groups and 20 min for 7.5%

Frequency of treatment:

- One exposure/ dose (4 treatments in total), separated by a minimum of 48 hours.
- One pre-exposure dose and one challange dose of Epinephrine (3 challange doses for the 7.5% dose).

Post exposure period:

at least 48 hours between the doses, 7 days after the final dose.

Dose / conc.:

20 000 ppm

Remarks:

Equivalent to 2%

Dose / conc.:

35 000 ppm

Remarks:

Equivalent to 3.5%

Dose / conc.:

50 000 ppm

Remarks:

Equivalent to 5%

Dose / conc.:

75 000 ppm

Remarks:

Equivalent to 7.5%

No. of animals per sex per dose:

- 20000, 35000, 50000 ppm: 6
- 75000 ppm: 5

Control animals:

yes

Details on study design:

This species and breed of animal is recognized as appropriate for cardiac function studies. The beagle dog was used because it is a widely used breed for which significant historical control data are available. The number of animals selected was the minimum needed to yield scientifically meaningful data.

ORGANISATION AND TREATMENT REGIMEN
Prior to exposure (during the pre-study acclimation period), an individual response to intravenous epinephrine administration was established for each individual dog using epinephrine doses starting at 2 μg/kg and increasing to 3, 4, 6 or 8 μg/kg, if necessary. The epinephrine doses were administered as a bolus injection (<5 seconds) via the cephalic vein. Time between escalating doses of epinephrine was at least 5 minutes or until the ECG returned to baseline. During this phase of the study, the dogs were exposed to air only via the muzzle-only exposure apparatus. The information gathered was used to select dogs for use on study and to establish the specific level of epinephrine each dog would receive during the test article exposure phase of the study. The epinephrine level selected for an individual dog was the highest dose level tested during the pre-study evaluation that did not elicit significant ECG findings (e.g., PVC).

Examinations:

CLINICAL OBSERVATIONS AND SURVIVAL
All animals were observed twice daily, once in the morning and once in the afternoon, for mortality and moribundity. Clinical examinations were performed on each dog prior to initiation of each exposure, continually during the exposure period and following each exposure upon return to their home cages. Detailed physical examinations were conducted on all animals on the day prior to the first day of exposure and on the last exposure day.

BODY WEIGHTS
Individual body weights were recorded on the first day of exposure and on the last day of exposure. Body weight changes were calculated for the corresponding intervals.

ELECTROCARDIOGRAPHIC EXAMINATIONS
Electrocardiograms (ECG) were recorded with a Burdick electrocardiograph. Modified leads I, II and III were used for electrocardiogram collection; ECG electrodes were placed on each limb. For the 2.0%, 3.5% and 5.0% test article exposures, ECG were recorded continuously throughout the pre-exposure epinephrine dosing, exposure to the test gas and for 5 minutes following administration of the challenge epinephrine dose (total of approximately 17 minutes). For the 7.5% test article exposure, ECG were collected for the entire exposure period (total of approximately 21 minutes). The points at which epinephrine was administered and when exposure to the test article was initiated were clearly marked on each ECG recording.
ECG recordings taken during exposure to the test article and after administration of the challenge epinephrine dose were compared to the ECG recordings made after administration of the pre-exposure epinephrine dose that was given in the absence of test article.

Details on results:

CLINICAL OBSERVATIONS AND SURVIVAL
All animals survived to study termination. There were no test article-related clinical observations. All clinical findings in the test article-treated groups were limited to single animals, were not observed consistently and/or were common findings for laboratory dogs of this age and breed.

BODY WEIGHTS
Body weights were unaffected by test article administration. There were no remarkable changes over the course of the study.

ELECTROCARDIOGRAPHIC EXAMINATIONS
Positive cardiac responses were noted for 0/6, 1/6 and 3/6 animals in the 20,000, 35,000 and 50,000 ppm groups, respectively. In the 75, 000 ppm group where the challenge doses of epinephrine were administered in ascending order, positive responses were noted for 0/5 animals at 0.2 μg/kg, 1/5 animals at 1.0 μg/kg and 2/4 animals at 2.0 μg/kg. The 2.0 μg/kg challenge dose of epinephrine was not administered to one animal due to the magnitude of effect noted following administration of the 1.0 μg/kg challenge dose. Positive responses were noted as occurrences of ventricular fibrillation, premature ventricular contractions or ventricular tachycardia.

Conclusions:

Based on the results of this study, muzzle-only vapor exposure to 35,000, 50,000 and 75,000 ppm Proprietary Refrigerant Blend in beagle dogs followed by administration of epinephrine resulted in episodes of premature ventricular contractions indicative of cardiac sensitization. Therefore, the no-observed-effect level (NOEL) was 20,000 ppm when maximum epinephrine injections were administered. In the study, at 75,000 ppm, a dose level of 0.2 μg/kg of epinephrine also did not cause cardiac arrhythmia.

Executive summary:

The objective of this study was to evaluate the cardiac sensitization potential of the test substance during acute inhalation exposure to various concentrations of the test article. The test article contained 29.8 to 31.3% CF3I. Cardiac sensitization refers to the potential for the test article to increase sensitivity of the heart to the pharmacological effects of epinephrine. The substance was administered via muzzle-only inhalation exposure (vapor) as acute exposures at concentrations of 2.0%, 3.5%, 5.0% and 7.5% (20,000, 35,000, 50,000 and 75,000 ppm, respectively). One group of 6 male dogs was used on this study. Each dog served as its own control. For the 2.0%, 3.5% and 5.0% groups, animals were administered a predetermined dose of epinephrine as a bolus injection via a cephalic vein approximately 5 minutes prior to exposure to the test article. Five minutes after exposure to the test article began, the animals were administered a challenge dose of epinephrine. For the 7.5% group, exposure to the test article was initiated and then 3 doses of epinephrine were administered 5 minutes apart. Following the final exposure, all dogs were returned to stock. All animals were observed twice daily for mortality and moribundity. Clinical examinations were performed prior to initiation of each exposure, continually during the exposure and immediately following each exposure period. Detailed physical examinations were performed and body weights were collected prior to the first day of exposures and at the completion of all exposures. Electrocardiographic data were recorded continuously throughout the pre-exposure epinephrine dosing, exposure to the test gas and for 5 minutes following administration of the challenge epinephrine dose (total of approximately 17 minutes).

All animals survived to study termination. There were no test article-related clinical observations. Body weights were unaffected by test article administration. Positive cardiac responses were noted for 0/6, 1/6 and 3/6 animals in the 20,000, 35,000 and 50,000 ppm groups, respectively. In the 75, 000 ppm group where the challenge doses of epinephrine were administered in ascending order, positive responses were noted for 0/5 animals at 0.2 μg/kg, 1/5 animals at 1.0 μg/kg and 2/4 animals at 2.0 μg/kg.

Based on the results of this study, muzzle-only vapor exposure to 35,000, 50,000 and 75,000 ppm Proprietary Refrigerant Blend in beagle dogs followed by administration of epinephrine resulted in episodes of premature ventricular contractions indicative of cardiac sensitization. Therefore, the no-observed-effect level (NOEL) was 20,000 ppm when maximum epinephrine injections were administered. In the study, at 75,000 ppm, a dose level of 0.2 μg/kg of epinephrine also did not cause cardiac arrhythmia.

Description of key information

Based on the results of this study, muzzle-only vapor exposure to 35,000, 50,000 and 75,000 ppm Proprietary Refrigerant Blend in beagle dogs followed by administration of epinephrine resulted in episodes of premature ventricular contractions indicative of cardiac sensitization. Therefore, the no-observed-effect level (NOEL) was 20,000 ppm when maximum epinephrine injections were administered. In the study, at 75,000 ppm, a dose level of 0.2 μg/kg of epinephrine also did not cause cardiac arrhythmia.

Additional information

Acute cardiac sensitization study in Beagle dogs with a test substance containing 29.8 to 31.3% CF3I

The objective of this study was to evaluate the cardiac sensitization potential of the test substance during acute inhalation exposure to various concentrations of the test article (WIL Research 2006). The test article contained 29.8 to 31.3% CF3I. Cardiac sensitization refers to the potential for the test article to increase sensitivity of the heart to the pharmacological effects of epinephrine. The substance was administered via muzzle-only inhalation exposure (vapor) as acute exposures at concentrations of 2.0%, 3.5%, 5.0% and 7.5% (20,000, 35,000, 50,000 and 75,000 ppm, respectively). One group of 6 male dogs was used on this study which received the 4 doses with intervals of at least 48 hours.. Each dog served as its own control. For the 2.0%, 3.5% and 5.0% groups, animals were administered a predetermined dose of epinephrine as a bolus injection via a cephalic vein approximately 5 minutes prior to exposure to the test article. Five minutes after exposure to the test article began, the animals were administered a challenge dose of epinephrine. For the 7.5% group, exposure to the test article was initiated and then 3 doses of epinephrine were administered 5 minutes apart. Following the final exposure, all dogs were returned to stock. All animals were observed twice daily for mortality and moribundity. Clinical examinations were performed prior to initiation of each exposure, continually during the exposure and immediately following each exposure period. Detailed physical examinations were performed and body weights were collected prior to the first day of exposures and at the completion of all exposures. Electrocardiographic data were recorded continuously throughout the pre-exposure epinephrine dosing, exposure to the test gas and for 5 minutes following administration of the challenge epinephrine dose (total of approximately 17 minutes).

All animals survived to study termination. There were no test article-related clinical observations. Body weights were unaffected by test article administration. Positive cardiac responses were noted for 0/6, 1/6 and 3/6 animals in the 20,000, 35,000 and 50,000 ppm groups, respectively. In the 75, 000 ppm group where the challenge doses of epinephrine were administered in ascending order, positive responses were noted for 0/5 animals at 0.2 μg/kg, 1/5 animals at 1.0 μg/kg and 2/4 animals at 2.0 μg/kg.

Based on the results of this study, muzzle-only vapor exposure to 35,000, 50,000 and 75,000 ppm Proprietary Refrigerant Blend in beagle dogs followed by administration of epinephrine resulted in episodes of premature ventricular contractions indicative of cardiac sensitization. Therefore, the no-observed-effect level (NOEL) was 20,000 ppm when maximum epinephrine injections were administered. In the study, at 75,000 ppm, a dose level of 0.2 μg/kg of epinephrine also did not cause cardiac arrhythmia.