NTP Study Reports
Abstract for TR-445
Toxicology and Carcinogenesis Studies of Scopolamine Hydrobromide Trihydrate (CAS No. 6533-68-2) in F344 Rats and B6C3F1 Mice (Gavage Studies)
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Chemical Formula: C17H22BrNO4 · 3H2O
Scopolamine hydrobromide trihydrate is used in ophthalmic preparations and as a preanesthetic sedative. Its major use is in transdermal patches for the treatment of motion sickness. Scopolamine hydrobromide trihydrate was selected for study because of considerable human exposure resulting from its use in prescription and over-the-counter preparations. Scopolamine was a suspect carcinogen because it contains an aliphatic epoxide moiety which may act as a biological alkylating agent. Male and female F344/N rats and B6C3F1 mice received scopolamine hydrobromide trihydrate (89% pure) in distilled water by gavage for 16 days, 14 weeks, or 2 years. Genetic toxicology studies were conducted in Salmonella typhimurium , cultured Chinese hamster ovary cells, and mouse peripheral blood erythrocytes.
16-DAY STUDY IN RATS
Groups of five male and five female rats were administered 0, 75, 150, 300, 600, or 1,200 mg scopolamine hydrobromide trihydrate/kg body weight in distilled water by gavage for 16 days. All rats survived to the end of the study. The final mean body weights and body weight gains of males receiving 600 and 1,200 mg/kg and the mean body weight gain of males receiving 300 mg/kg were significantly lower than those of the control group. Clinical findings included bilateral pupillary dilation in all dosed animals and red eyelids in males and females receiving 1,200 mg/kg. There were no significant treatment-related gross or microscopic lesions.
16-DAY STUDY IN MICE
Groups of five male and five female mice were administered 0, 150, 250, 450, 900, or 1,800 mg scopolamine hydrobromide trihydrate/kg body weight in distilled water by gavage for 16 days. One male and two females receiving 1,800 mg/kg and one female receiving 150 mg/kg died during the study. The final mean body weights and body weight gains of dosed mice were similar to those of the control groups. Clinical findings related to scopolamine hydrobromide trihydrate administration included bilateral pupillary dilation and squinting in all dosed males and females. The relative liver weights of males receiving 1,800 mg/kg and of females in all dosed groups were significantly greater than those of the control groups. There were no significant treatment-related gross or microscopic lesions.
14-WEEK STUDY IN RATS
Groups of 10 male and 10 female rats were administered 0, 15, 45, 135, 400, or 1,200 mg scopolamine hydrobromide trihydrate/kg body weight in distilled water by gavage for 14 weeks. One female receiving 45 mg/kg, one male and one female receiving 135 mg/kg, six males and one female receiving 400 mg/kg, and eight males and seven females receiving 1,200 mg/kg died during the study. The final mean body weights and mean body weight gains of all dosed males and females were significantly lower than those of the control groups. Clinical findings included bilateral pupillary dilation in all dosed males and females and reddening of the eyes in 15 mg/kg males and 135, 400, and 1,200 mg/kg males and females.
Hematocrit, hemoglobin concentration, and/or erythrocyte count in male and female rats receiving 45 mg/kg or greater were slightly higher than those of the control groups. In general, these changes were most prominent in rats in the 400 and 1,200 mg/kg groups. Higher hematocrit, hemoglobin concentration, and erythrocyte count were likely due to hemoconcentration from dehydration (relative erythrocytosis). A minimal to mild mature neutrophilia, evidenced by higher segmented neutrophil numbers than in the control group, occurred in all dosed male rats.
Sperm morphology and vaginal cytology parameters in dosed rats were similar to those in the control groups.
Nine male and five female dosed rats died from esophageal obstructions consisting of feed and bedding material in the posterior pharynx. Tracheal obstruction occurred concurrently with esophageal obstruction as a result of food build-up in the oropharyngeal region. This condition is considered to be secondary to the inhibitory effects of scopolamine hydrobromide trihydrate on salivary gland secretions and on esophageal smooth muscle involved in swallowing. There were no other significant treatment-related gross or microscopic findings.
14-WEEK STUDY IN MICE
Groups of 10 male and 10 female mice were administered 0, 15, 45, 135, 400, or 1,200 mg scopolamine hydrobromide trihydrate/kg body weight in distilled water by gavage for 14 weeks. One male receiving 135 mg/kg and two males and one female receiving 1,200 mg/kg died during the study. The final mean body weights and mean body weight gains of all dosed male groups and females receiving 45 mg/kg and above were significantly lower than those of the control groups. Clinical observations included bilateral pupillary dilation, hyperactivity, and hypoactivity.
A minimal to mild mature neutrophilia, similar to that which occurred in the 14-week rat study, occurred in male mice receiving 45 mg/kg or greater. As in the rat study, there was no microscopic evidence of inflammation that could account for the neutrophilia.
The estrous cycle length of 1,200 mg/kg females was significantly greater than that in the control group.
There were no significant treatment-related gross or microscopic lesions.
2-YEAR STUDY IN RATS
Groups of 60 male and 60 female rats were administered 0, 1, 5, or 25 mg scopolamine hydrobromide trihydrate/kg body weight in distilled water by gavage for 104 weeks. Ten males and ten females from each dose group, excluding the 1 mg/kg female group, were evaluated at 15 months.
Survival, Body Weights,
Clinical Findings, and Ophthalmic Examination Findings
The survival rates of female rats receiving
1 and 25 mg/kg were significantly lower than that of the control
group. Mean body weights of 1 and 5 mg/kg males and females were
similar to those of the controls throughout the study. However,
mean body weights of 25 mg/kg males and females were generally
lower than those of the control groups after about week 25. Clinical
findings included bilateral pupillary dilation in all dosed males
and females. Ophthalmic examination revealed no significant findings.
Hematology
Compared to controls, hematocrit was
slightly higher in the 25 mg/kg male rats, similar to the effects
observed in the 14-week study; this is consistent with dehydration
resulting in hemoconcentration. Reticulocyte numbers in the 25
mg/kg female rats were slightly lower than those in the controls.
This result is consistent with the lower body weights, and thus
a decreased nutritional status, exhibited by these animals.
Plasma Scopolamine
Determinations
The serum scopolamine concentrations
were 6 ng scopolamine/mL serum for the 5 mg/kg female sample and
12 and 28 ng/mL for the 25 mg/kg male and female samples, respectively.
The amounts of scopolamine in the other serum samples were below
the minimum detection limit (4 ng/mL) of the analysis method.
Neurobehavioral
Findings
Horizontal motor activity of 25 mg/kg
females was significantly greater than that of the control group
on days 90, 180, and 360. Startle response of 5 and 25 mg/kg females
was significantly lower than that of the control group on day
90. On day 180, passive avoidance of 25 mg/kg males was significantly
lower than that of the control group.
Pathology Findings
The incidences of adenoma of the pituitary
gland pars distalis decreased with increasing dose in both male
and female rats; however, this trend was only significant in males
(males: vehicle control, 19/49; 1 mg/kg, 17/49; 5 mg/kg, 13/50;
25 mg/kg, 10/50; females: 20/50, 13/60, 14/50, 10/50). The incidences
of adenoma of the pituitary gland pars distalis in 25 mg/kg males
and all groups of dosed females were below the NTP historical
control range. The incidences of hyperplasia were not significantly
different from those in the control groups.
The incidences of mononuclear cell leukemia in 25 mg/kg males and females were significantly lower than those of the control groups (males: 33/50, 21/50, 26/50, 24/50; females: 20/50, 6/60, 13/50, 4/50). The incidence of mononuclear cell leukemia in females receiving 25 mg/kg was well below the NTP historical range.
2-YEAR STUDY IN MICE
Groups of 70 male and 70 female mice were administered 0, 1, 5, or 25 mg scopolamine hydrobromide trihydrate/kg body weight in distilled water by gavage for 104 to 105 weeks. Ten control animals and ten animals from each dose level were evaluated at 15 months.
Survival, Body Weights,
Clinical Findings, and Ophthalmic Examination Findings
Survival of dosed males and females
was similar to that of the controls. The mean body weights of
males and females receiving 1 mg/kg were similar to those of the
control groups throughout the majority of the study. The mean
body weights of 5 mg/kg males and females were slightly lower
than those of the controls. The mean body weights of males and
females receiving 25 mg/kg were lower than those of the control
groups after week 13. Clinical findings included bilateral pupillary
dilation in all dosed male and female groups. Ophthalmic examination
revealed no significant findings.
Hematology
Hematocrit, hemoglobin concentration,
and erythrocyte count in 25 mg/kg female mice were slightly lower
than those in the control group. These results are consistent
with development of a minimal normocytic, normochromic nonresponsive
anemia. The anemia may be related to the lower body weights exhibited
by these animals and are presumed to be due to a decreased nutritional
status.
Pathology Findings
The combined incidences of hepatocellular
neoplasms (adenoma or carcinoma) occurred with a significant negative
trend in males and females (males: vehicle control, 30/50; 1 mg/kg,
33/50; 5 mg/kg, 14/50; 25 mg/kg, 15/50; females: 22/51, 21/50,
16/50, 9/51). The combined incidences of hepatocellular neoplasms
in 5 and 25 mg/kg males were within the NTP historical control
range. The incidences of clear cell foci and eosinophilic foci
in dosed male groups, and eosinophilic foci in 25 mg/kg females,
were significantly lower than those of the control groups.
The incidences of many spontaneously occurring nonneoplastic lesions were significantly lower in dosed mice than in the control groups and usually decreased with increasing dose. These included kidney nephropathy, alveolar epithelial hyperplasia, hyperplasia of the pancreatic islets, bone marrow myelofibrosis, hyperplasia of the pituitary gland pars distalis, cystic hyperplasia of the uterus, and hematopoietic cell proliferation of the spleen. The decreased incidences of these spontaneous lesions were most likely a result of lower body weights in dosed animals.
GENETIC TOXICOLOGY
Scopolamine hydrobromide trihydrate did not induce mutations in any of five strains of Salmonella typhi murium , with or without S9 metabolic activation enzymes, nor did it induce sister chromatid exchanges in cultured Chinese hamster ovary cells, with or without S9. A weakly positive response was obtained, however, in a chromosomal aberrations test conducted in cultured Chinese hamster ovary cells with very high doses of scopolamine hydrobromide trihydrate in the presence of S9; without S9, no increase in aberrations was noted. Despite the evidence for chromosomal damage observed in vitro , no increase in the frequencies of micronucleated normochromatic erythrocytes was observed in peripheral blood samples of male or female mice exposed to scopolamine hydrobromide trihydrate for 14 weeks by gavage.
CONCLUSIONS
Under the conditions of these 2-year gavage studies, there was no evidence of carcinogenic activity of scopolamine hydrobromide trihydrate in male or female F344/N rats or B6C3F1 mice administered 1, 5, or 25 mg/kg.
Synonyms: Scopolamine hydrobromide, 6,7-epoxytropan-3-yl, euscopol, hydroscine hydrobromide, hyoscine bromide, (-)-hyoscine hydrobromide, hysco, isoscopil, scopolammonium bromide, (s)-tropate hydrobromide trihydrate, l -tropyl-a-scopine
Male F344/N Rats |
Female F344/N Rats |
Male B6C3F1 Mice |
Female B6C3F1 Mice |
|
---|---|---|---|---|
Doses | 0, 1, 5, or 25 mg/kg in water by gavage | 0, 1, 5, or 25 mg/kg in water by gavage | 0, 1, 5, or 25 mg/kg in water by gavage | 0, 1, 5, or 25 mg/kg in water by gavage |
Body weights | 25 mg/kg group lower than control group | 25 mg/kg group lower than control group | 5 and 25 mg/kg groups lower than control group | 5 and 25 mg/kg groups lower than control group |
2-Year survival rates |
20/50, 14/50, 22/50, 28/50 | 34/50, 17/60, 26/50, 22/50 | 40/50, 39/50, 39/50, 39/50 | 33/51, 36/50, 37/50, 38/51 |
Nonneoplastic effects |
None | None | None | None |
Neoplastic effects | None | None | None | None |
Levels of evidence of carcinogenic activity |
No evidence | No evidence | No evidence | No evidence |
Genetic toxicology | |
Salmonella typhimurium gene mutations: | Negative with and without S9 in strains TA97, TA98, TA100, TA1535, and TA1537 |
Sister chromatid exchanges Cultured Chinese hamster ovary cells in vitro : |
Negative with and without S9 |
Chromosomal aberrations Cultured Chinese hamster ovary cells in vitro : |
Negative without S9; weakly positive with S9 |
Micronucleated erythrocytes Mouse peripheral blood in vivo : |
Negative in male and female mice |
Report Date: March 1997
Pathology Tables, Survival and Growth Curves from NTP 2-year Studies
Target Organs & Incidences from 2-year Studies
Web page last updated on April 14, 2009