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EC number: 931-292-6
CAS number: 308062-28-4
The objective of the study was to obtain scientific data to determine
the histopathological effects of the skin at treatment sites after
repeated dermal exposure to the test substance over 91 days with a 28
day interim sacrifice.
Fifty ICR-Swiss CD-1 mice (25M, 25F) per group were assigned to each of
the following treatment groups. The dose volume for each group was 0.1ml
with the control group being sterile water. Treatment groups were 0.27%
DDAO (0.27 mg per application) and 1.33% DDAO (1.33 mg per application).
An area of 2 X 3 cm of the dorsal area of all animals was clipped and
treated with 0.1ml of appropriate treatment 5 days per week.
All animals were observed daily for signs of general health, mortality
and gross skin irritation effects. Gross signs of toxicity and body
weights were recorded on a weekly basis throughout the study.
After 28 days (21 dermal applications) 10 males and 10 females from each
group were sacrificed and necropsied. The remaining animals continued on
the treatment regimen until the termination of the study. At study
termination (90-92 days from initiation of the study), 5 females from
each group were sent to the sponsor for in-vitro skin penetration
studies. The remainder of the animals were sacrificed and necropsied.
At the 28 and 91 day necropsies, the following tissues were preserved in
formalin: brain, pituitary, thyroid, thymus, small and large intestine,
heart, trachea, axillary and mesenteric lymph nodes, stomach, esophagus,
uterus, skin from treated and dorsal non-treated areas, lungs, liver,
spleen, kidneys, adrenals, urinary bladder, ovary, testis, eyes, aorta,
pancreas, and carcass. The skin tissues from treated animals and dermal
non-treated areas were processed and examined histopathologically.
No mortalities were attributed to treatment and there were no
significant differences in body weights in any animals throughout the
study. Gross necropsies at interim or terminal sacrifice did not reveal
any substance related lesions with the exception of skin effects at the
site of treatment for the 0.27% group after 28 days applications of the
test substance. Repeated applications of 1.33% over the 28 days resulted
in slight to moderate erythema and scaling in most animals. The
histological examinations of the 0.27% dose group after 28 days
exhibited dermal irritation consisting of minimal to slight acanthosis.
The dermal irritation effects were more pronounced in animals dosed with
1.33% consisting of acathosis and hyperkeratosis.
The gross observations of skin effects of animals treated with 1.33% and
sacrificed after 91 days were more severe than the irritation effects
observed at 28 days. The gross observations of the skin effects of
animals treated with 0.27% were erythema and scaling in most animals
compared to no significant irritative effects at 28 days. When
histological examinations were conducted, minimal dermal irritation was
present in 11 male and the 10 female mice treated with 0.27% and
consisted of minimal or slight acanthosis. In mice treated with 1.33%, a
more pronounced dermal irritation was present with minimal acathosis in
one mouse, slight acanthosis in 11 mice and moderate acanthosis in 13
Gonadal tissues were examined for gross pathology and no
treatment-related effects were detected.
Repeated dermal applications of 0.1ml of 0.27% DDAO (0.27
mg/application) for five days/week for 28 and 91 days resulted minimal
to mild acanthosis. Local effects were more pronounced with the repeated
dermal applications of 0.1ml of 1.33% DDAO (1.33 mg/application) for
five days/week, resulting in both acanthosis and hyperkeratosis. No
systemic effects, based on mortality, clinical signs and gross necropsy
observations were identified at either dose level; however, no
histopathology was performed except on skin.
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