Summaries of Toxicity Studies on Benfuresate
Research and Development Department, Hoechst Schering AgrEvo K.K.
(Received February 20, 1995)
DESCRIPTION OF THE TEST CHEMICAL
Benfuresate is the active ingredient of cor-responding commercially available
herbicide formulation. It has been synthesized by Schering AG in 1970s during, andfound that the compound shows excellent herbicidal activities to Cyperaceae weeds,
such as Cyperus rotundas and Cyperus esculentus. In Japan, this compound has been
investigated since 1987 for the herbicidal activities, and it is registered to control
Eleocharis kuroguwai in paddy field which is difficult to control with existingherbicides.
To provide an adequate data basis for an evaluation of health risks for users ofcrop protection agents containing benfuresate and for an assessment of the health risk
for consumers of treated food products, numerous toxicological studies with thetechnical product and 2% granular formulation were conducted.
The chemical structure and physico-chemical properties of benfuresate are given
below.
Common name: Benfuresate (BSI/ISO)
Chemical name: 2,3-Dihydro-3,3-dimethylbenzofuran-5-yl ethanesulfonate(IUPAC)
CH3
Structural formula:
CH3CH2SO 2O

CH3O

Molecular formula: C12H16O4S
Appearance: Brown viscous liquid which may solidify at room temperature
Boiling point: 239-242˚C (atomosphcric pressure)
Vapour pressure: 1.4 x 10-3 (20˚C)
Solubility (25˚C): Water 0.261 g/l. Soluble in methanol, acetone, dichloromethane,toluene and ethyl acetate
Partition coefficient (log Pow): 2.41
Stability: Stable for 31 days under pH 5, 7 and 9 in 25˚C and 37˚C
Photolysis: Half-life time is about 7 days for aqueous solution
ACUTE TOXICITY STUDIESThe results of acute toxicity studies are summarized in Table 1.
1. Acute Oral and Dermal Toxicity Study
On oral administration, benfuresate technical material and 2% granule formulation

Table 1 Acute toxicity test.

Technical

Formulation(2% granule)
Code: NS 112

RouteSpecies

LD50 (mg/kg)

Oral

Rata)
Mouseb)M, F >4000
M, F >5000

DermalRatc)

M, F > 5000

Inhalation

Ratd) (4hr. LC50) M, F >5. 343 (mg/l)

Oral

Rate)
Mousef)M, F >5000
M, F > 5000

DermalRatg)

M, F >2000

a-e)

AgrEvo UK Ltd., 1991.
Hazleton UK, 1990.
e-g)
Huntingdon Research Centre, 1992.
M : male, F : female.
d)

is unlikely to indicate particular toxic signs in rats and mice.
No harmful skin reactions nor toxic signs by dermal toxicity study with either
technical or formulation were observed.
2. Acute Inhalation Toxicity Study
One group of ten rats (five males and five females) of the Crl: CD(SD)BR strain
was exposed to technical benfuresate at a single chamber concentration of 5.343 mg/l
by inhalation (head-only) over a period of 4 hr. The corresponding nominal concentration
was 6.455 mg/l. A group of ten rats (five males and five females) was similarly
exposed to filtered air as a control. Exposure was followed by an observation periodof 14 days.
The exposure chamber temperature recorded for both the control and treated groups
was 19˚C, and the chamber relative humidity was in the range 26 to 58%. The
chamber air flow rates were 20.0 and 14.2 l/min for the control and treated group.
The mean mass median aerodynamic diameter of the particles in the atmosphere was
1.73 µm.
There were no deaths during the course of the study. Treatment-related clinicalsigns occurring during the day of exposure included piloerection, salivation, nasal
secretion and coldness to touch. Clinical signs did not persist beyond the day of
exposure. There were no treatment related effects on body weight or absolute andrelative lung weights and no evidence of specific target organ toxicity.

IRRITATION STUDIES
1. Primary Dermal Irritation Study on Rabbits
A skin irritation potential of technical benfuresate was evaluated according toOECD guideline 404 for the testing of chemicals, and a skin irritation of 2% granule
was assessed according to the Japanese testing guideline for primary dermal irritation.
0.5 ml of technical benfuresate or 0.5 g of 2% granule were applied under a 2.5 cm
square gauze pad to the intact skin of a shaved area. Each treatment site was covered
with "Elastoplast" elastic adhesive dressing for a four period.
The skin was grossly examined 30 to 60 min after the exposure period and them
daily for 3 days on technical benfuresate and for 4 days on 2010 granule.
No signs of irritancy were observed following a single-semi-occlusive applicationof technical benfuresate or 2% granule to intact rabbit skin for 4 hr.
(Technical: Schering Agrochemicals Ltd., 1990)(Granule: Huntingdon Research Centre, 1992)
2. Primary Eye Irritation Study on Rabbits
Evaluation of eye irritation properties of technical benfuresate and 2% granule wasmade according to OECD guidelines for the testing of eye irritancy. 0.1 ml of technicalbenfuresate and approximately 100 mg of 2% granule, the weight occupying a volumeof 0.1 ml were placed into the lower lid of one eye of each animal. The eyelids werethen gently held together for one second before releasing. The contralateral eye
remained untreated and served as a control. The eyes were grossly exarnined 1 hr
after the exposure period and then 1, 2, 3 and 4 days after instillation for technicalbenfuresate and 7 days was included for 2% granule.
There were no signs of irritation seen in any animal.
(Technical: Schering Agrochemicals Ltd., 1990)(Granule: Huntingdon Research Centre, 1992)
3. Dermal Sensitization Study on Guinea Pigs
The potential of technical benfuresate and the 2% granule to induce delayed contact
hypersensitivity were evaluated according to the Buehler test.
Induction comprised topical occlusive exposure of 10 female albino guinea pigs of
Dunkin/Hartley strain to undiluted benfuresate and suspension of 70% w/w of 2%
granule in distilled water for 6 hr, once per week for 3 weeks. Treated and naive
Guinea pigs were challenged 14 days after the last induction dose with undiluted
benfuresate and the suspension of 2% Study granule.
Technical benfuresate and 2% granule exhibited no evidence of dermal sensitization
potential.
(Technical: Schering Agrochemicals Ltd., 1990)(Granule: Huntingdon Research Centre, 1992)

SUB-CHRONIC TOXICITY STUDIES
1. Rat 90-Day Dietary Repeat Dose Study
Group of 10 male and 10 female CD(SD) rats were fed diet containing 0, 200, 500,
1250 or 3125 ppm (equivalent to 0, 14, 35, 88 and 218 mg/kg/day) of technicalbenfuresate for 13 weeks.
There were no effect on clinical signs, body weight, food consumption, water
consumption, urinalysis, and haematological parameters, considered to be related totreatment with test article. Kidney weight relative to body weight was increased by
10% in males fed 3125 ppm.
Treatment also caused an increase in the incidence and severity of hyaline droplet
degeneration and eosinophilic cytoplasmic inclusion bodies in the proximal tubularepithelium of the kidneys of male rats
The no adverse effect level following subchronic dietary administration of technicalbenfuresate to rat for 13 weeks was 1250 ppm, equivalent to 88.2 mg/kg/day.
(Schering Agrochemicals Ltd., 1990)
2. Mouse Dietary 90 Day Study
Groups of 10 male and 10 female mice were fed diet containing 0, 1000, 3000,
9000 or 18,000 ppm (equivalent to 0, 236, 846, 2772 or 5454 mg/kg/day) of technicalbenfuresate for at least 90 days. Supplementary groups of 10 male and 10 female
mice were included at each dose level for blood sampling only.
At 18,000 ppm, there were three treatment-related deaths in males. Body weightgain was reduced by 9 and 7% and food consumption was increased by 20 and 38%
in males and females, respectively. Water consumption was also increased by 16% infemales. In males, kidney Weight was decreased (18%) and relative liver weightincreased (16%) Macroscopic effects seen in the kidneys of 4/10 males included
swelling, paleness and irregular shape and size. Effects seen in the liver of 1/10 males
included depressed lobes. Treatment at 18,000 ppm also caused papillary necrosis,
tubular degeneration and luminal dilatation of the proxirnal tubules in the kidneys of
4/10 males and 1/10 females.
At 9000 ppm, there were two deaths in males. Reduced body weight gain andincreased food and water consumption, as well as microscopic kidney changes in
1/10 females, were similar to those seen at 18,000 ppm. A reduction in the incidenceof fat deposition in hepatocytes of females was also noted.
At 3000 ppm, reduced body weight gain, increased food consumption and reduced
fat deposition in hepatocytes of females were similar to those seen at 9000 ppm.
No treatment-related effects were seen at 1000 ppm. On the basis of results obtained,
it was concluded that the no effect level (NOEL) was 1000 ppm, equivalent to a daily
intake of 236 mg/kg.
(Schering Agrochemicals Ltd., 1991)

3. Dog 90-Day Repeat Dose Study by Gavage
Groups of 4 male and 4 female beagle dogs were dosed daily by gavage at 0, 10,
100 and 1000 mg/kg bodyweight of technical benfuresate for 90 days.
There were no clinical signs directly attributable to administration of benfuresate,
the four deaths observed during the study, and two deaths in the highest dose groupwere considered to be treatment and others being due to misdosing.
Bodyweight and food consumption were unaffected by treatment. No treatment
related effects were detected by clinical examinations, ophthalmoscopy,
electrocardiography and laboratory investigations.
Renal effects at 1000 mg/kg were characterised by increased kidney weight, changes
in gross appearance at necropsy and histopathological evidence of papillary necrosis
and scarring, tubular dilation and interstitial nephritis.
Liver weight was increased in female dogs at 1000 mg/kg, but this was not associatedwith any histopathological change.
No other treatment related changes were detected at necropsy or by organ weight
analysis and histopathological examination. The no effect level for daily dosing ofbenfuresate to dogs was 100 mg/kg.
(Schering Agrochemicals Ltd., 1988)
CHRONIC TOXICITY/ONCOGENICITY STUDIES
1. Combined Dietary Chronic Toxicity and Oncogenicity Study in Rat
Groups of 50 male and 50 female CD (SD) rats were fed diet containing 0, 60, 600
or 6000 ppm (equivalent to 0, 3.07, 30.6 or 318 mg/kg/day) of technical benfuresatefor 27 months. In addition, supplementary groups of 20 male and 20 female rats
treated at the same dietary levels were killed after 12 months.
The high dose was selected as the predicted maximum tolerated dose (MTD) basedon comprehensive range finding information.
Treatment at 6000 ppm resulted in persistently decreased weight gain (10-18%)
and food intake (6-8%) in both sexes. Food conversion efficiency was also impaired(17%) in females at this dose level. Bilirubin (total) was variably reduced in both
sexes whilst females had slightly lower absolute liver and heart weights and kidneyweight relative to body weight was elevated by 14%. Histopathology showed areduction in the severity and incidence of margination of the cytoplasm of hepatocytes
in females and a lower incidence of chronic progressive nephropathy and epithelial
hyperplasia of the forestomach in both sexes.
At 600 ppm, overall body weight gain was reduced by 11 and 6% in males andfemales, respectively. Kidney weight relative to body weight was increased in femalesby 11% The only other finding attributable to treatment was a reduction in theseverity and incidence of margination of the cytoplasm of hepatocytes of females andepithelial hyperplasia of the forestomach in both sexes.
No treatment-related effects were observed at 60 ppm.

It was concluded that benfuresate was not oncogenic in the rat at dose levels up to6000 ppm (equivalent to a daily intake of 318 mg/kg/day) .
Treatment at 6000 ppm resulted in clear evidence of toxicity including a marked
reduction in weight gain indicating that a maximum tolerated dose was achieved.
The no-effect level was 60 ppm equivalent to 3.07 mg/kg/day.
(Schering Agrochemicals Ltd., 1990)
2. Mouse Dietary Opecogenicity Study
Groups of 50 male and 50 female CD1(CR) BR mice were fed diet containing 0,300, 3000 or l0,000 ppm (equivalent to 0, 55, 561 or 1989 mg/kg/day) of technicalbenfuresate for 80 weeks.
In males dosed at 10,000 ppm, there was an earlier onset and higher incidence ofmortality. Food consumption was increased (11%). Terminal body weight was markedly
and statistically significantly lower (14%) in females which was considered to be
partly due to a significantly higher intake (20%) of benfuresate than in the corresponding
males. Renal papillary necrosis was observed in 16/50 males and was consideredfatal in 13 of these resulting in the increased mortality at this dose level. In females
renal papillary necrosis was considered fatal in 4/50 animals. There was also an
increase in the incidence of pyelonephritis in both sexes. It is probable that there wasa palatability problem due to the very high dose level in females, as up to one third of
the apparent food consumption was scattered on the cage floor.
In females treated at 3000 ppm, terminal body weight was statistically signiflcantly
lower (11%) than controls and renal papillary necrosis was observed in 3/50 animals.
There were no other effects at this dose level.
At 300 ppm, terminal body weight was not statistically significantly different fromcontrol. There were no treatment-related histopathological lesions detected in either
sex.
Technical benfuresate was not oncogenic in the mouse at very high dose levels up
to l0,000 ppm (equivalent to a daily intake of 1989 mg/kg/day) ..
Treatment at 10,000 ppm resulted in clear evidence of toxicity including a reduction
in survival in males and a reduction in body weight (females), renal papillary necrosis
and pyelonephritis in both sexes, indicating that a maximum tolerated dose wasexceeded.
The overall NOEL was 300 ppm (equivalent to a daily intake of 55 mg/kg/day) .
(Schering Agrochemicals Ltd., 1992)
3. Dog 12 Month Gavage Repeat Dose Study
Groups of 4 male and 4 female beagle dogs were dosed daily for 12 months by
gavage with 0, 4 or 40 mg/kg of technical benfuresate. Another group of 6 male and6 female dogs were dosed concurrently at 400 mg/kg/day subsequently reduced to300 mg/kg/day and then 200 mg/kg (administered twice daily from day 86). The
control animals received only 1% methyl cellulose in distilled water.
Oral administration of technical benfuresate to dogs at dose levels of up to 40
mg/kg elicited no adverse effects.
A single dose of 400 mg/kg or 300 mg/kg resulted in tremors, convulsions (withand without relaxation), rapid respiration, salivation and frothing at the mouth.
Prostration and reduced activity were also noted. These signs were generally seen
within 3 hr of dosing and had regressed within 7 hr.
Following twice daily administration of 200 mg/kg, convulsions were seen in one
male prior to being sacrificed in extremis on study day l03. Other signs attributed totreatment included circling behaviour and reduced activity in two animals and tremors
in one animal. These signs were generally intermittent and most animals were devoidof treatment-related clinical signs for the rest period of the study. In females, water
consumption was increased by 17-27% on 3/4 occasions and a reduction in red cellparameters was noted after 4, 7 and 12 months. Red cell parameters were also
decreased at 12 months in males. Very severe papillary necrosis was seen in thekidney of one male and one female had chronic pyelonephritis.
Daily administration of single bolus doses of either 400 or 300 mg/kg were found
to exceed the maximum tolerated dose leading to twice daily administration of 200
mg/kg which was tolerated. The target organ was the kidney.
The no observed effect level (NOEL) was 40 mg/kg/day.
(Schering Agrochemicals Ltd., 1992)
REPRODUCTIVE AND TERATOGENICITY STUDIES
1. Rat Multigeneration Study
Technical benfuresate was administered in the diet at concentrations of 0, 60, 600
and 6000 ppm.
After about 10 weeks treatment (maturation period), groups of 30 male and 30
female CD(SD) strain F0 generation rats were paired to produce the F1 litters fromwhich the F1 generation was derived.
The selected F1 generation animals were treated for about 11 weeks and thenpaired to produce the F2 litters. The study was terminated when these offsprings had
reached weaning. The following findings were observed in groups dosed at 600 and
6000 ppm ;Adults : At 6000 ppm, group mean body weight gain of both sexes was reduced
during the maturation period in both the F0 and F1 generations. Reductions wereabout 16 and 13% in males and 16 and 9% in females for the F0 and F1 generations
respectively.
During gestation, mean body weight gain was reduced by about 10 and 14% in F0
and F1 generation females respectively.

Relative kidney weights of F0 adults were slightly increased. In F0 males alone,
this was associated with an increased incidence of minimal hyaline droplet accumulationin the renal proximal tubular epithelium.
Litters : At 6000 ppm, in both litterings, group mean litter weights and pup mean
body weights were significantly lower than in controls by Day 25 post-partum. In the
F1->F2 litters, group mean litter weights were slightly lower throughout lactation.
Litter size was slightly lower than in controls from birth to weaning in the F1->F2
Iitters.
At 600 ppm, group mean pup body weight gain was slightly reduced (by about9%) by Day 25p.p. in the F0->F1 Iitters alone although group mean litter weights
tended to be marginally lower than controls in both littermgs.
The only effect on reproduction was a marginal lowering of litter size in littersfrom the F1 generation at 6000 ppm, the highest dose level.
On the basis of results obtained no effect levels were judged to be;
Toxicity: 600 ppm (equivalent to 4.9 mg/ kg/day)
Reproduction : 60 ppm (equivalent to 50 mg/kg/day)(Schering Agrochemicals Ltd., 1992)
2. Rat Teratology Study
Dose levels of 0 (control), 3, 55 or 1000 mg/kg, in 1 % w/v methyl-cellulose indistilled water, were administered once per day by gavage to groups of 25 time-matedCD(SD) strain females from Day 6 to Day 15 post coitum inclusive. On Day 20 theanimals were killed, litter values were determined and foetuses subsequently examinedfor visceral and skeletal changes. The following findings were observed.
Maternal fiudings : Treatment with technical benfuresate was associated with adose-related increase in transient post dosing salivation. At 1000 mg/kg/day, this signoccurred in all females, generally throughout the treatment period, and was associatedwith wet coats and, occasionally, brown staining of the coat. Smaller numbers ofanimals at lower dose levels exhibited salivation for shorter time periods.
At 1000 mg/kg/day, there was a progressive and significant increase in water
consumption throughout the treatment period. Differences from control in water
consumption persisted to termination but decreased after the end of treatment.
There were no other conclusive treatment-related responses at lower dose levels.
Litter fiudings: Litter parameters appeared unaffected in all treatment groups, as
judged by embryofoetal survival, foetal growth and morphological development.
On the basis of results obtained, the no effect level (NOEL) for maternal parameters
was 3 mg/kg/day and for embryofoetal development was 1000 mg/kg/day.
(Huntingdon Research Centre, 1992)
3. Rabbit Teratology Study

Dose levels of 0 (control), 50, 200 or 800 mg/kg, in 1 % carboxymethylcellulose
in distilled water, were administered once per day by gavage to groups of 16 matedfemales of Chinchilla rabbits from Day 6 to Day 18 post coitum inclusive. On Day 28
post coitum, the dams were killed, litter values were determined and foetuses
subsequently examined for visceral and skeletal changes. The following findings
were observed.
Maternal fiudings: Two females at 200 mg/kg died during the dosing period, being
attributed to intubation error. There were no mortalities, behavioural changes or
necropsy findings in the mated females considered to be related to treatment with test
article.
At 800 mg/kg, weight gain was slightly retarded during the first five days of
dosing and food consumption was reduced during the first nine days of dosing andduring the last four days of the study. At 200 and 50 mg/kg, weight gains and foodconsumption were similar to those of controls throughout the study. There were notreatment-related differences in the values for water consumption, liver and kidneyweights and the reproduction parameters-overall pregnancy rate, incidence of total
resorption, numbers of implantations, pre- and post-implantation losses and numbersof live fetuses.
Litter findings: Litter parameters were not affected by treatment, as judged by
foetal growth and morphological development.
On the basis of results obtained, the no effect level (NOEL) for maternal parameters
was 200 mg/kg/day and there was no evidence of an embryotoxic or teratogenic
effect up to the highest dosage examined, 800 mg/kg/day.
(Research & Consulting Company, 1988)
MUTAGENICITY STUDIES
1. Bacterial Reverse Mutation Assay
The potential of benfuresate to induce reverse gene mutations was evaluated in Ames
plate incorporation assays employing the histidine auxotrophic Salmonella typhimurium
strains TA1535, TA1537, TA1538, TA98 and TA100 in both presence and absenceof an Aroclor 1254-induced rat liver metabolic activation system (S-9). A top doselevel of 5000 µg/plate was chosen and other dose levels used were 1500, 500, 150
and 50 µg/plate. The test system was validated with concurrent positive control using
9-aminoacridine (9-AC), N-ethyl-N'-nitro-N-nitrosoguanidine (ENNG), 2nitrofluorene and 2-aminoanthracen (2-AA). A number of revertant colonies did notincrease when cultured with or without metabolic activation system at any concentrationof test article, indicating benfuresate did not induce gene mutation.
The potential of benfuresate to induce reverse gene mutations was also evaluatedin the tryptophane auxotrophic Escherichia coli strain WP2 uvrA in both the presence
and absence of rat liver metabolic activation system. The same dose levels as those inthe study with S. typhimurium was used, and the test system was validated withconcurrent positive control using ENNG and 2-AA. No mutagenic effect was observed.
(Huntingdon Research Centre, 1991)
2. Mammalian Cytogenetics
The potential of benfuresate to induce chromosomal aberrations in human
lymphocytes cultured in vitro.
Concentrations of technical benfuresate dissolved in ethanol, used for metaphaseanalysis were 15, 75 and 150 µg/ml in the absence of S-9 and 75, 375 and 750 µg/ml
in the presence of S-9. No significant increase in the number of aberrant cells wasobserved in treated groups compared with the solvent control. Both positive control
compounds, ethylmethane sulphonate for the absence of S-9 and cyclophosphamide
for the presence of S-9 caused statistically significant increases in the proportion of
metaphase spread containing aberration. It is concluded that when tested up to thelimits of solubility in ethanol, benfuresate showed no evidence of clastogenic activity
and therefore no evidence of mutagenic activity in this in vitro cytogenetic assay.
(Huntingdon Research Centre, 1984)
3. Bacterial DNA Repair Test
The potential of benfuresate to damage DNA was evaluated in vitro in a bacterial
recombination assay using Bacillus subtilis strains H17 (rec+) and H45 (rec-) both in
the presence and absence of rat liver metabolic activation system. A top dose level of5000 µg/plate, and other dose levels, 1500, 500, 150 and 50 µg/ plate were used.
Kanamycin and streptomycin as negative controls, AF-2, and 2-AA as positive controls
were used to confirm the sensitivity, efficacy and integrity of this test system. No
genetic darnage was observed.
(Huntingdon Research Centre, 1991)
GENERAL PHARMACOLOGY
1. Effect of General Behaviour of Mice
Benfuresate was assessed for the behavioural and autonomic effects following asingle oral dose of 62.5, 125, 250, 500, 1000 or 2000 mg/kg to 5 male ICR mice perdose level using modified Irwin dose-range test. Irregular and slow breathing, transitory
increase of motor activity and slight depression of motor activity were seen in alltreated groups, and findings of midriasis were observed in animals administered 250
mg/kg. Tremors in 1000, 2000 mg/kg, ventricumbent, no gripping strength andsialorrhoea in 2000 mg/kg were seen. One animal in 2000 mg/kg group died by 1 day
after dosing, and the additional findings, gait spastic, spasmodic twitches, abolishedpina and light-pupil reflex, prolonged response time and marked hypothermia wereobserved in this animal.
Findings of hypothermia were seen in animals treated with 500, 1000 and 2000

mg/kg. The peak of occurrence of these findings was about 1 to 3 hr after dosing, andthe flndings recovered completely within 1 day after dosing.
2. Effects on Respiratory and Circulatory Systems
The effects on respiratory and circulatory parameters in 5 anaesthetised male rabbits
administered intravenously at doses of 1 and 10 mg/kg were examined.
Benfuresate at a dose of 10 mg/kg produced a significant decrease of mean bloodpressure and a significant increase of respiration rate which was observed fromimmediate after dosing to 5 min comparing to solvent control.
In a group at a dose of 1 mg/kg, no specific finding was recorded.
3. Effects on Spontaneous Motility of Isolated Ileum
Antagonist action of benfuresate against acetylcholine, histamine and barium chloride
was assessed at concentrations of 3.0 x 10-8 to 3.0x 10 -5 g/ml with the ileum isolated
from Guinea pigs. Significant inhibitions were observed on the contraction inducedwith three antagonists at the concentration of l0-5 g/ml, comparing to solvent control.
4. Effects on Gastro-intestinal Propulsion
Activated charcoal suspension was given orally to mice 60 min after oral
administration of benfuresate at 250, 500 and 1000 mg/kg. Twenty minutes afteradministration of the suspension, the animals were sacrificed and propulsion of thecharcol to intestine determined.
No effect of benfuresate was observed in all treated groups, while atropine sulfate
at 20 mg/kg used as a positive control showed significant inhibition of propulsion ofactivated charcoal.
5. Effects on Neurowascular Junction
The effect of benfuresate on neuromuscular junction was assessed using phrenic
nerve diaphragm specimens from male rats. The change in contraction of isolated rat
diaphragm muscle by electrical stimulation of phrenic nerve and muscle was measured
following treatment with benfuresate at concentrations of 3 x l0-7 to 3 x l0-5 g/ml.
Compared to ethanol treated animals, benfuresate at a concentration of 3 x l0-5
g/ml produced significant increase of contraction indirectly by stimulation of nerve.
No effect was observed for contraction of diaphragm muscle by direct stimulation.
6. Effect on Blood Coagulation System
The effects of benfuresate on blood coagulation system were assessed in 5 malerats administered by gavage at a dose of 1000 and 2000 mg/kg.
Benfuresate did not produce any effects on thrombin, prothrombin or partially
activated thromboplastin time either in 1000 mg/kg or in the 2000 mg/kg.

7. Effect on Haemolysis in vitro
The potential of benfuresate to cause haemolysis was assessed by mixing 0.02 and
0.2 mg/ml benfuresate with blood of rabbit, and measuring the optical density at 541
nm. No significant differences from the 1% ethanol/saline group observed in both
treated group suggesting that benfuresate did not cause haemolvsis.
(Nihon Schering K.K., 1992)
SUMMARY
Technical benfuresate was of very low acute oral and dermal and low acuteinhalational toxicity to rodents. Repeat dose studies in the rat, mouse and dog showed
the material to be well tolerated with the maximally tolerated doses of 318, 561 and
400 mg/kg/ day, respectively. Histopathology showed the kidney to be the main
target organ in all three species. The principal findings in the kidney, found following
subchronic exposure in the rat and following subchronic/chronic exposure in themouse and dog were papillary necrosis and dilatation and/or degeneration of theproximal tubules (and collecting ducts in 'rats). These findings were associated withelevated kidney weights in the rat and dog, pyelonephritis in the mouse and dog andinterstitial nephritis in the rat and dog.
The liver was also a target organ at dose levels above the MTD in the rat andmouse as indicated by swelling of the periportal hepatocytes and centrilobular
enlargement, respectively.
There was no evidence of oncogenicity in the mouse or rat and the NOEL in themost sensitive species, the rat, was 3 mg/kg/day.
Technical benfuresate was non-genotoxic, non-irritant, had no effect on reproduction
or fertility and was not a skin sensitiser.
The compound was rapidly and completely absorbed. Tissue residues were low
and declined rapidly. The highest levels were found in the kidney and fat after 6 hr.
Metabolism of the compound in the rat was rapid and complete as was elimination,
which was predominantly via the urine.
The compound showed weak pharmacological effects on the nervous systemfollowing oral administration and the circulatory and respiratory systems, but only
after intravenous dosage.
The acute toxicity of metabolites, process intermediates and formulations ofbenfuresate were low.
It is concluded therefore that under the recommended conditions of use both technicalbenfuresate and formulations are unlikely to present hazard to operators or the public
who may consume negligible residues from treated produce.
Contact

Product Development Group, R+D Department Hoechst Schering AgrEvo K.K., 410-33, Akasaka, Minato-ku, Tokyo 107, Japan
問合せ
ヘキスト・ジューリング・アグレボ株式会社研究開発部製品開発グループ〒107東京都港区赤坂4-10-33