Avermectin A1a, 25-cyclohexyl-5-O-demethyl-25-de(1-methylpropyl)-

Endpoint summary

Description of key information

Oral:

Two 90-day studies are available.

Rat study: No treatment related gross or histological findings except for an increase in absolute and relative liver weights for the high dose females. The no-observed-effect-level (NOEL) for this study is 2.0 mg/kg/day (Fisher, 1990).

Dog study: The only significant clinical finding was that of mydriasis in 1 of 6 high dose animals. There was no effect of treatment on body weights, vital signs, serum chemistry, hematology or urinalysis values. The no-observed-effect-level (NOEL) in beagle dogs is 0.1 mg/kg (Stadnicki, 1990).

Key value for chemical safety assessment

Repeated dose toxicity: via oral route - systemic effects

Link to relevant study records

Reference

Reference 1

Endpoint:

sub-chronic toxicity: oral

Type of information:

experimental study

Adequacy of study:

key study

Study period:

From 15 May to 24 Aug 1989

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Study run to a method comparable with current guidelines and to GLP

Qualifier:

according to guideline

Guideline:

other: Drug Safety Evaluation Standard Procedures

Deviations:

no

GLP compliance:

yes

Limit test:

no

Species:

rat

Strain:

Long-Evans

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source:
- Age at study initiation:
- Weight at study initiation:
- Fasting period before study:
- Housing: Rats were individually housed in hanging stainless steel cages with wire mesh fronts and floors. There were 60 cages per rack and the rats were transferred to freshly cleaned cages every two weeks.
- Diet (e.g. ad libitum): All rats were fed a standard ground laboratory diet (Agway Prolab RMH 3200) ad libitum.
- Water (e.g. ad libitum): Drinking water was supplied ad libitum through an automatic watering system with founts in each cage. Water was obtained from a municipal system subject to regulations of the Environmental Protection Agency facility.
- Acclimation period:

ENVIRONMENTAL CONDITIONS
- Temperature (°F): 70±2
- Humidity (%): 50±5
- Air changes (per hr):Total air volume in the room was circulated at the rate of 18 times per hour with air filtered through 85-90% efficiency filters, then through HEPA filters.
- Photoperiod (hrs dark / hrs light): The room was illuminated by fluorescent light 12 hours per day (7:00 a.m.-7:00 p.m.).

Route of administration:

oral: gavage

Vehicle:

other: sesame oil

Details on oral exposure:

PREPARATION OF DOSING SOLUTIONS:

VEHICLE
- Justification for use and choice of vehicle (if other than water):
- Concentration in vehicle: 0.1, 0.4, 1.6 mg per mL
- Amount of vehicle (if gavage): 0.5 mL per 100g body weight
- Lot/batch no. (if required):
- Purity:

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

The analysis of dosing solutions for drug content during study weeks 1, 10, and 13 indicated that the intended concentrations were used.

Duration of treatment / exposure:

93-96 days (males), 99-102 days (females)

Frequency of treatment:

daily

Dose / conc.:

0.5 mg/kg bw/day (actual dose received)

Dose / conc.:

2 mg/kg bw/day (actual dose received)

Dose / conc.:

8 mg/kg bw/day (actual dose received)

No. of animals per sex per dose:

20 animals/sex/dose

Control animals:

yes, concurrent vehicle

Positive control:

None stated

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: No data
- Time schedule:
- Cage side observations checked in table [No.?] were included.

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: at least twice daily

BODY WEIGHT: Yes
- Time schedule for examinations: prior to the designated start of the study and weekly thereafter

FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study):
- Food consumption for each animal determined and mean daily diet consumption calculated as g food/kg body weight/day: Yes
- Compound intake calculated as time-weighted averages from the consumption and body weight gain data: No data

FOOD EFFICIENCY:
- Body weight gain in kg/food consumption in kg per unit time X 100 calculated as time-weighted averages from the consumption and body weight gain data: No data

OPHTHALMOSCOPIC EXAMINATION: Yes
Ophthalmoscopic examinations were performed on the high dose and control animals once prior to the start of this study and once during the study, and all animals at the end of the study.

HAEMATOLOGY: Yes
- Time schedule for collection of blood: on days 30-33, 58-61, and at the end of the study
- Anaesthetic used for blood collection: No data
- Animals fasted: Yes
- How many animals:
- white blood cell count (WBC), red blood cell count (RBC), hemoglobin concentration (HGB), hematocrit (HCT), white blood cell differential count, platelet count (PLAT) were examined.

CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: on days 30-33, 58-61, and at the end of the study
- Animals fasted: Yes
- How many animals:
-Sodium(NA), potassium (K), calcium (CA), chloride (CL), glucose (GLUC), blood urea nitrogen (BUN), creatinine (CREA), alanine aminotransferase (SGPT or ALT), aspartate aminotransferase (SGOPT or AST), sorbitol dehydrogenase (SDH), 5'nucleotidase (5NT), total protein (T.P.), and albumin (ALBM) were examined.

URINALYSIS: Yes
- Time schedule for collection of urine: on days 30-33, 58-61, and at the end of the study
- Metabolism cages used for collection of urine: No data
- Animals fasted: Yes
- Volume vioded during 21 to 22 hours, specific gravity, pH, protein, blood, sugar, urobilinogen, bilirubin, and ketones were examined.

NEUROBEHAVIOURAL EXAMINATION: Yes / No / No data
- Time schedule for examinations:
- Dose groups that were examined:
- Battery of functions tested: sensory activity / grip strength / motor activity / other:

OTHER: A sediment analysis was performed on samples with a 3+ value for blood, or the presence of unusual color.

Sacrifice and pathology:

The animals were fasted overnight and necropsied on days 93 to 102. Folliowing the intraperitoneal administration of pentobarbital and exsanguination, the internal organs were grossly examined. Absolute organ weights were recorded for both kidneys (combined), prostate, testis (individual), and ovaries (combined). Tissues from the following organs, as welll as any gross abnormalities, were placed in 10% neutral buffered formalin:
Kidneys, Pancreas, Urinary bladder, Colon, Liver (two sections), Testes, Spleen, Epididymes, Mesebteric lymph node, Prostate, Thymus, Seminal vesicle, heart, Ovaries, Lund, Uterus, Trachea, Skin, Thyroids, Mammary gland, Adrenals, Brain, Pituitary, Spinal cord, Salivary gland, Eye, Esophagus, Harderian glang, Stomach, Sternum (bone and marrow), and Duo denum
After fixatuion the above tissues were trimmed, embedded in paraffin, sectioned and stained with hematoxylin and eosin. Liver and kidney sections from each animal were also routinely stained with periodic acid-Schiff's reagents. All tissues from the high dose and control animals as well as those intermediate and lose dose animals with gross findings were examined microscopically. Variations from normal were recorded utilizing an on line computer program.

Other examinations:

Systemic exposure of test animals was verified by monitoring plasma drug concentrations in a subset of 3 rats/sex/dose level. Blood was collected from the retro-orbital sinus into heparinized tubes 3 hours after dosing on days 3 and 87 of the study.

Statistics:

Body weights and organ weights (liver, kidney and testes) at necropsy were analyzed by single classification analysis of variance (1). If the p-value associated with the F-test of the analysis of variance was less than 0.05, Dunnett's test was applied to test for significant difficant differences between treatment and control means (2). Individual p-values are not listed, however statistical significance is indicated by flags such that #=5% and ##=1%. For the purpose of data interpration, statistical significance was not considered to automatically imply toxicological significance.
Conversely, the absence of a statistically significant comparision was not considered to imply the lack of a biologically important effect. Fpr the other organ weights recorded, only means and standard deviations were calculated.

Clinical signs:

no effects observed

Mortality:

no mortality observed

Body weight and weight changes:

no effects observed

Food consumption and compound intake (if feeding study):

no effects observed

Food efficiency:

not specified

Ophthalmological findings:

no effects observed

Haematological findings:

no effects observed

Clinical biochemistry findings:

no effects observed

Urinalysis findings:

no effects observed

Behaviour (functional findings):

no effects observed

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Gross pathological findings:

no effects observed

Histopathological findings: non-neoplastic:

no effects observed

Histopathological findings: neoplastic:

not specified

Details on results:

Clinical Observations:
Test substance administration had no adverse effect on weight gain during the 3 month period of this study. Similary, food consumption at all levels appeared tobe unaffected by treatment. There were no treatment-related changes in the appearance or behavior of any study animal. No treatment-related ocular lesions were observed.

Body Weight:
The body weight decrements of 12-15% for the high dose females and males at the start of this study were attributed to maternal exposure at 1.0 mg/kg. At a dose level substantially above the apparent maximum tolerated dose for neonatal exposure (8.0 mg/kg versus 1.0 mg/kg), the initial body weight decrements were largely reversed by the end of the 3 month treatment period.

Clinical Pathology:
There were no treatment related changes in cinical chemistry, hematology, or urinalysis determinations. Any control ranges or are not concidered tobe of toxicologic significance.

Plasma Drug Concentrations:
All drug-treated animals tested were systemically exposed to the test substance, and plasma concentrations were dose-dependent on both sampling days.

Gross and Histopathology:
There were no treatment related gross or histological findings except for an increase in absolute and relative liver weights for the high dose females.

Dose descriptor:

NOAEL

Effect level:

8 mg/kg bw/day (actual dose received)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

gross pathology

histopathology: non-neoplastic

Dose descriptor:

NOEL

Effect level:

2 mg/kg bw/day (actual dose received)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: There was no clinical, laboratory, gross or microscopic evidence of toxicity.

Critical effects observed:

not specified

Conclusions:

The test substance, an avermectin antiparasitic, was administered daily by oral gavage to Long-Evans rats for 92-102 consecutive days at dose levels of 0.5, 2.0 or 8.0 mg/kg/day following continuous exposure in utero and lactation. Plasma drug concentrations in this study increased with dose, indicating that animals were systemically exposed to the drug. The body weight decrements of 12-15% for the high dose females and males at the start of this study were attributed to maternal exposure at 1.0 mg/kg. At a dose level substantially above the apparent maximum tolerated dose for neonatal exposure (8.0 mg/kg versus 1.0 mg/kg), the initial body weight decrements were largely reversed by the end of the 3 month treatment period. Clinical evaluation of treated animals did not reveal any signs of toxicity. There were no changes in clinical chemistry, hematology, or urinalysis parameters due to the test substance exposure. There were no treatment related gross or histological findings except for an increase in absolute and relative liver weights for the high dose females.
The no-observed-effect-level (NOEL) for this study is 2.0 mg/kg/day.

Reference 2

Endpoint:

sub-chronic toxicity: oral

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

From 26 Jun to 27 Sep 1989

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Study run to a method comparable with current guidelines and to GLP.

Qualifier:

according to guideline

Guideline:

other: Drug Safety Evaluation Standard Procedures

Deviations:

no

GLP compliance:

yes

Limit test:

no

Species:

dog

Strain:

Beagle

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Marshall Farms, North Rose, NY
- Age at study initiation: 9-10 months
- Weight at study initiation:
- Fasting period before study:
- Housing: Dogs were individually housed in stainless steel cages that were wall mounted over stainless steel excretion throughs.
- Diet (e.g. ad libitum): All dogs were fed a standard ground laboratory dog chow (Agway Respond 2000) once daily.
- Water (e.g. ad libitum): Drinking water was supplied ad libitum through an automatic watering system with founts in each cage. Water was obtained from a municipal system subject to regulations of the Environmental Protection Agency facility.
- Acclimation period: at leasst one month

ENVIRONMENTAL CONDITIONS
- Temperature (°F): 70±2
- Humidity (%): 50±5
- Air changes (per hr):Total air volume in the room was circulated at the rate of 18 times per hour with air filtered through 85-90% efficiency filters, then through HEPA filters.
- Photoperiod (hrs dark / hrs light): The room was illuminated by fluorescent light 12 hours per day (7:00 a.m.-7:00 p.m.).

Route of administration:

oral: gavage

Vehicle:

other: sesame oil

Details on oral exposure:

PREPARATION OF DOSING SOLUTIONS:

VEHICLE
- Justification for use and choice of vehicle (if other than water):
- Concentration in vehicle: 0.1 or 0.3 mg of active moiety/mL
- Amount of vehicle (if gavage): 1 mL/kg body weight
- Lot/batch no. (if required):
- Purity:

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

During weeks 1, 5, 8, and 13, weighed samples (approximately 2.0 grams) were submitted to the Analytical Department for concentration and homogeneity determinations. All samples consisted of weighed aliquots obtained pre and post dose from each dosing solution. All dosing solutions were of acceptable (±15%) potency.

Duration of treatment / exposure:

92 days

Frequency of treatment:

daily

Dose / conc.:

0.1 mg/kg bw/day (actual dose received)

Dose / conc.:

0.3 mg/kg bw/day (actual dose received)

No. of animals per sex per dose:

3 animals/sex/dose

Control animals:

yes, concurrent vehicle

Positive control:

None stated

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: No data
- Time schedule:
- Cage side observations checked in table [No.?] were included.

DETAILED CLINICAL OBSERVATIONS: Yes
All animals were observed at least twice daily for changes in appearance and behaiver and for clinical signs of pharmacologic or toxicologic effects.
Electrocardiographic tracings (leads I, II, III, aVR, aVL, aVF, and CV6LL) and indirect systolic blood pressure recordings were obtained from each animal twice prior to the start of the study and at 1, 2 and 3 months.
Vital signs (heart rate, respiratory rate, and rectal temperature) were obtained from all dogs twice prior to the onset of drug administration, and prior to dosing and approximately 2 hours post-dose on day 1, and at 1, 2 and 3 months.

BODY WEIGHT: Yes
- Time schedule for examinations: Individual weights were recorded twice prior to the start of treatment, on day 1 prior to dosing and weekly thereafter.

FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study):
- Food consumption for each animal determined and mean daily diet consumption calculated as g food/kg body weight/day: Yes
- Compound intake calculated as time-weighted averages from the consumption and body weight gain data: No data

FOOD EFFICIENCY:
- Body weight gain in kg/food consumption in kg per unit time X 100 calculated as time-weighted averages from the consumption and body weight gain data: No data

OPHTHALMOSCOPIC EXAMINATION: Yes
Ophthalmoscopic examinations were performed by a clinical veterinarian once prior to the start of the study and at the end of the study (days 86-88).

HAEMATOLOGY: Yes
- Time schedule for collection of blood: twice prior to the onset of drug administration, and on days 28-30, 58-60, and 90-92 during the study.
- Anaesthetic used for blood collection: No data
- Animals fasted: Yes
- How many animals: all
- white blood cell count (WBC), red blood cell count (RBC), hemoglobin concentration (HGB), hematocrit (HCT), mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), mean corpuscular hemoglobin concentration (MCHC), platelet count (PLT), white blood cell differential count were examined.

CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: twice prior to the onset of drug administration, and on days 28-30, 58-60, and 90-92 during the study
- Animals fasted: Yes
- How many animals: all
-Sodium(NA), potassium (K), calcium (CA), chloride (CL), glucose (GLUC), blood urea nitrogen (BUN), creatinine (CREA), alanine aminotransferase (ALT), aspartate aminotransferase ( AST), alkaline phosphatase (AlkPh), sorbitol dehydrogenase (SDH), Gamma glutamyl transpeptidase(GGTP), total protein (TProt), total bilirubin (TBili), albumin (ALBM) and creatinine phosphokinase (CPK) were examined.

URINALYSIS: Yes
- Time schedule for collection of urine: twice prior to the onset of drug administration, and on days 28-30, 58-60, and 90-92 during the study.
- Metabolism cages used for collection of urine: No data
- Animals fasted: Yes
- Volume vioded during approximately 20 hours, color, specific gravity, pH, protein, blood, sugar, urobilinogen, bilirubin, and ketones were examined.

NEUROBEHAVIOURAL EXAMINATION: No data
- Time schedule for examinations:
- Dose groups that were examined:
- Battery of functions tested: sensory activity / grip strength / motor activity / other:

OTHER: Plasma Drug Concentrations: Blood samples were collected approximately 3 hours after dosing on days 30 and 92.

Sacrifice and pathology:

GROSS PATHOLOGY: No data
HISTOPATHOLOGY: No data

Statistics:

None stated

Clinical signs:

no effects observed

Mortality:

no mortality observed

Body weight and weight changes:

no effects observed

Food consumption and compound intake (if feeding study):

no effects observed

Food efficiency:

not specified

Ophthalmological findings:

effects observed, treatment-related

Haematological findings:

no effects observed

Clinical biochemistry findings:

no effects observed

Urinalysis findings:

no effects observed

Behaviour (functional findings):

not specified

Organ weight findings including organ / body weight ratios:

not specified

Gross pathological findings:

not specified

Histopathological findings: non-neoplastic:

not specified

Histopathological findings: neoplastic:

not specified

Details on results:

CLINICAL SIGNS AND MORTALITY
All animals survived the 3 month dosing period. All groups of animals, including controls, exhibited "flushing" (i.e. reddening) of the ears and gums, and incidences of loose formed or unformed stools.
Vital Signs:
No treatment related changes in these parameters were observed during this study.
Electrocardiograms, Blood Pressures and Ophthalmoscopic Examinations:
No drug-induced changes in electrocardiograms were noted during the study. Although these values fluctuated among individual animals this was considered normal and unrelated to compound administration.

BODY WEIGHT AND WEIGHT GAIN
There was no effect of treatment on body weights.

OPHTHALMOSCOPIC EXAMINATION
Mydriasis, ranging from mild to moderate, was diagnosed in high dose female No. 18 during weeks 3, 7, 9, 11 and 13 by the clinical veterinarian. This diagnosis was based on the comparison of the pupillary diameters of the drug treated dogs with the contol dogs. This is not a unique finding as mydriasis has been diagnosed in two previous studies with test substance and has also been observed in ivermectin (MK-0933) dosed beagles (Lankas and Gordon, 1989). All other animals were within acceptable normal limits with regard to mydriasis and no other drug related ocular changes were noted.

HAEMATOLOGY
No drug-related haematology changes were observed in this study.

CLINICAL CHEMISTRY
Slight elevations in alkaline phosphatase (AlkPh) values occurred in 3 of 6 low dose animals (2 male; 1 female) and 2 of high dose animals (1male; 1 female).These changes were not considered to be related to treatment.

URINALYSIS
No drug-related urinalysis changes were observed in this study.

OTHER FINDINGS
The plasma concentration data indicate that all dosed females were exposed to drug in a dose-dependent manner. High dose females exhibited slightly higher plasma concentrations than their male counterparts on days 30. Day 92 values in low dose animals revealed a similar finding.

Dose descriptor:

NOAEL

Effect level:

0.3 mg/kg bw/day (actual dose received)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

gross pathology

histopathology: non-neoplastic

Dose descriptor:

NOEL

Effect level:

0.1 mg/kg bw/day (actual dose received)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: The only siginificant clinical finding was that of mydriasis in 1 of 6 high dose animals.

Critical effects observed:

not specified

Conclusions:

Test substance was administered by gavage in sesame oil to beagle dogs (3/sex/dose level) at doses of 0.1 or 0.3 mg/kg/day. All animals survived the 3 month dosing period. The only significant clinical finding was that of mydriasis in 1 of 6 high dose animals. In general, there was no effect of treatment on body weights, vital signs, serum chemistry, hematology or urinalysis values. No drug-related effects were noted in electrocardiograms or indirect systolic blood pressure. Dose dependent plasma concentrations of the test substance were observed in this study.
Based on the results of this study, the no-observed-effect-level (NOEL) in beagle dogs is 0.1 mg/kg.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

NOAEL

8 mg/kg bw/day

Study duration:

subchronic

Species:

rat

Quality of whole database:

1 (reliable without restriction)

Repeated dose toxicity: inhalation - systemic effects

Endpoint conclusion

Endpoint conclusion:

no study available

Repeated dose toxicity: dermal - systemic effects

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information

Oral:

Two 90 -day studies are available.

Rat study (Fisher, 1990): The test substance, an avermectin antiparasitic, was administered daily by oral gavage to Long-Evans rats for 92-102 consecutive days at dose levels of 0.5, 2.0 or 8.0 mg/kg/day following continuous exposure in utero and lactation. Plasma drug concentrations in this study increased with dose, indicating that animals were systemically exposed to the drug. The body weight decrements of 12-15% for the high dose females and males at the start of this study were attributed to maternal exposure at 1.0 mg/kg. At a dose level substantially above the apparent maximum tolerated dose for neonatal exposure (8.0 mg/kg versus 1.0 mg/kg), the initial body weight decrements were largely reversed by the end of the 3 month treatment period. Clinical evaluation of treated animals did not reveal any signs of toxicity. There were no changes in clinical chemistry, hematology, or urinalysis parameters due to the test substance exposure. There were no treatment related gross or histological findings except for an increase in absolute and relative liver weights for the high dose females. The no-observed-effect-level (NOEL) for this study is 2.0 mg/kg/day.

Dog study (Stadnicki, 1990): Test substance was administered by gavage in sesame oil to beagle dogs (3/sex/dose level) at doses of 0.1 or 0.3 mg/kg/day. All animals survived the 3 month dosing period. The only significant clinical finding was that of mydriasis in 1 of 6 high dose animals. In general, there was no effect of treatment on body weights, vital signs, serum chemistry, hematology or urinalysis values. No drug-related effects were noted in electrocardiograms or indirect systolic blood pressure. Dose dependent plasma concentrations of the test substance were observed in this study. Based on the results of this study, the no-observed-effect-level (NOEL) in beagle dogs is 0.1 mg/kg.

Justification for classification or non-classification

Oral: No significant toxic effects observed at any dose level tested in 90-day repeated dose study both on dogs and rats.

Therefore in accordance with Regulation (EC) No. 1272/2008 Table 3.9.1, this substance should not be classified for STOT RE endpoint.