Registration Dossier

Administrative data

Description of key information

Acute toxicity data on Guanidine hydrochloride are available for the oral, inhalation and dermal route. The data available from three studies for the 
oral route all indicate LD50 values for Guanidine hydrochloride in the range between 773.6 and 1120 mg/kg bw.
The LC50 from an inhalation study for females is 3.181 mg/L air (LC50 for males = 7.655 mg/L air).
The dermal LD50 is > 2000 mg/kg bw.

Key value for chemical safety assessment

Acute toxicity: via oral route

Link to relevant study records
Reference
Endpoint:
acute toxicity: oral
Type of information:
experimental study
Adequacy of study:
key study
Study period:
1984-01-19 to 1984-02-14
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Study conducted according to national (US) guideline, comparable to OECD guideline
Qualifier:
according to
Guideline:
other: EPA TS-792 Acute exposure, oral toxicity. Health effects test guidelines, EPA, August 1982; EPA 560/6-82-001
Deviations:
no
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 401 (Acute Oral Toxicity)
Deviations:
no
GLP compliance:
yes
Test type:
standard acute method
Limit test:
no
Species:
rat
Strain:
Sprague-Dawley
Sex:
male/female
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Bantin Kingman, Fremont, CA
- Weight at study initiation: 150 – 255 g
- Fasting period before study: yes, over night
- Housing: individually
- Diet (e.g. ad libitum): Certified Purina Rodent Chow Diet 5062, ad libitum
- Water (e.g. ad libitum): ad libitum
- Acclimation period: 11 d

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 23.2°C to 25°C
- Humidity (%): 40 to 53%
- Air changes (per hr): no data
- Photoperiod (hrs dark / hrs light): 12/12
Route of administration:
oral: gavage
Vehicle:
water
Details on oral exposure:
VEHICLE
- Concentration in vehicle: no data
- Amount of vehicle (if gavage): 0.74-1.02 mL/animal in males, 0.59-0.74 mL/animal in females
- Justification for choice of vehicle: test substance is soluble in water
Doses:
0, 278, 360, 464, 600, 775 mg/kg bw (expressed as active ingredient Guanidine), corresponding to 0, 453.14, 756.32, 978, 1263.25 mg/kg bw Guanidine hydrochloride
No. of animals per sex per dose:
9 in treated groups; 5 in vehicle control and cage control
Control animals:
yes
Details on study design:
- Duration of observation period following administration: 14 days
- Frequency of observations and weighing:
Clinical signs, mortality: after 2 and 4 h, daily thereafter
Body weight: twice weekly
- Necropsy of survivors performed: yes; completet gross necropsy
- Other examinations performed: histopathology of CNS for animals with neurological symptoms
Statistics:
Probit analysis
Sex:
male
Dose descriptor:
LD50
Effect level:
556.5 mg/kg bw
Based on:
other: Guanidine
95% CL:
492.3 - 630.9
Sex:
female
Dose descriptor:
LD50
Effect level:
474.6 mg/kg bw
Based on:
other: Guanidine
95% CL:
402 - 562.7
Sex:
male
Dose descriptor:
LD50
Effect level:
907.1 mg/kg bw
Based on:
test mat.
Remarks:
Guanidine hydrochloride
95% CL:
802.45 - 1 028.4
Sex:
female
Dose descriptor:
LD50
Effect level:
773.6 mg/kg bw
Based on:
test mat.
Remarks:
Guanidine hydrochloride
95% CL:
655.3 - 917.2
Mortality:
- vehicle control: 0/5 males, 0/5 females died
- cage control: 0/5 males, 0/5 females died
- 278 mg/kg bw: 0/9 males, 0/8 females died
- 360 mg/kg bw: 0/9 males, 2/8 females died
- 464 mg/kg bw: 2/9 males, 5/9 females died
- 600 mg/kg bw: 5/9 males, 4/7 females died
- 775 mg/kg bw: 9/9 males, 9/9 females died
(reduced total numbers are due to misdosing; those animals were removed from the study)
Clinical signs:
most frequent clinical signs:
- central nervous system-neuromuscular disturbances at all dose groups( 80 of 86 animals)
- increased startle reflex, hyperactivity, and disorientation up to 464 mg/kg bw, recovery within one week
- in the two higher dose groups (600 and 775 mg/kg bw), incressed startle reflex, hyperactivity (as indicated by random jumping, tremors and/or twitching), and depressed grasping and righting reflexes within 4 hours of dosing were observed; most animals in these dose groups died within 24 h

- gastrointestinal tract symptoms (hunched posture, increased salivation with some staining of the muzzle, and diarrhea) in 53/86 animals at all dose levels, but severity was dose-dependent


Body weight:
no significant effects
Gross pathology:
- no test compound-related lesions in the CNS (gross and light microscopic examination)
- the only test compound-related findings were in the gastrointestinal tract (black/serosanguinous material in the stomach, focal depression in the glandular mucosa of the stomach, black and diffuse red areas in the glandular mucosa of the stomach, black and tarry material in the intestine, black and tarry feces)
- in surviving animals no test compound-related gross lesions were reported; 2 male and 1 female rats had a unilateral dilated renal pelvis, which is considered incidential
Other findings:
- Histopathology:
Several rats exhibited central nervous system (CNS) signs. Some rats that exhibited CNS signs died and some others survived. The cerebrum, brainstem and cerebellum of 4 animals died were examined by light microscopy and no lesions were observed.

Sex       Endpoint       Effect level                                     95% CL

male       LD10       441.8 mg/kg bw (Guanidine base) 326.3 — 497.9

female       LD10       321.4 mg/kg bw (Guanidine base) 209.1 — 383.9

male       LD90       701.1 mg/kg bw (Guanidine base) 621.1 — 956

female       LD90       700.8 mg/kg bw (Guanidine base) 584.8 — 1089.9

Interpretation of results:
other: Acute toxicity Category 4
Remarks:
Criteria used for interpretation of results: other: CLP, EU GHS (Regulation (EC) No 1272/2008)
Conclusions:
The oral LD50 for Guanidine hydrochloride in rats was 907.1 mg/kg bw (95% c.i. 802.45 - 1028.4) in males and 773.6 mg/kg bw (95% c.i 655.3 - 917.2) in females. Thus, Guanidine hydrochloride has to be classified for Acute oral toxicity, Category 4.
Executive summary:

In an acute oral toxicity study similar to OECD guideline 401, groups of fasted Sprague-Dawley rats (9/sex) were given a single oral dose of Guanidine hydrochloride (>98% purity, 61.8% base equivalent Guanidine) in water at doses of 0, 278, 360, 464, 600 and 775 mg/kg bw (expressed as Guanidine base), corresponding to 0, 453.14, 756.32, 978, 1263.25 mg/kg bw Guanidine hydrochloride and observed for 14 days.

No mortality occurred in the lowest dose group. 0/9 males, 2/8 females in the 360 mg/kg bw dose group died; 2/9 males, 5/9 females in the 464 mg/kg bw dose group; 5/9 males, 4/7 females in the 600 mg/kg bw dose group and 9/9 males, 9/9 females in the 775 mg/kg bw dose group. Reduced total numbers are due to misdosing; those animals were removed from the study.

Clinical signs were observed in the CNS (increased startle reflex, hyperactivity, and disorientation) and in the gastro-intestinal tract (hunched posture, increased salivation with some staining of the muzzle, and diarrhea) in all dose groups. However, there were no microscopic findings in cerebrum, brainstem and cerebellum of animals with CNS symptoms.

Gross pathology revealed black/serosanguinous material in the stomach, focal depression in the glandular mucosa of the stomach, black and diffuse red areas in the glandular mucosa of the stomach, black and tarry material in the intestine, black and tarry feces.

In the surviving animals no test compound-related gross lesions were reported.

Several rats exhibited central nervous system (CNS) signs. Some rats that exhibited CNS signs died and some others survived. The cerebrum, brainstem and cerebellum of 4 animals died were examined by light microscopy and no lesions were observed.

Oral LD50 Males = 556.5 mg Guanidine/kg bw (95% C.I. 492.3 - 630.9 mg/kg bw)

Oral LD50 Females = 474.6 mg Guanidine/kg bw (95% C.I. 402 - 562.7 mg/kg bw)

corresponding to:

Oral LD50 males = 907.1 mg/kg bw (95% c.i. 802.45 - 1028.4) Guanidine hydrochloride

Oral LD50 females = 773.6 mg/kg bw (95% c.i 655.3 - 917.2) Guanidine hydrochloride

Thus, Based on these data, Guanidine hydrochloride has to be classified for Acute toxicity, Category 4.

Endpoint conclusion
Endpoint conclusion:
adverse effect observed
Dose descriptor:
LD50
773.6 mg/kg bw
Quality of whole database:
The available studies are guideline-conform and of high quality (key study: RL1, supporting studies RL2).

Acute toxicity: via inhalation route

Link to relevant study records
Reference
Endpoint:
acute toxicity: inhalation
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Guideline study
Qualifier:
according to
Guideline:
OECD Guideline 403 (Acute Inhalation Toxicity)
GLP compliance:
yes
Test type:
standard acute method
Limit test:
no
Species:
rat
Strain:
Sprague-Dawley
Sex:
male/female
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Charles River (UK) Ltd., Margate
- Age at study initiation: 6 to 8 weeks old
- Weight at study initiation: 140 - 200 g
- Fasting period before study: no data
- Housing: groups of 5 animals by sex in grid-floor stainless steel cages
- Diet (e.g. ad libitum): ad libitum; SQC Rat and Mouse Maintenance Diet No. 1 Expanded, Special Diets Services Ltd. Witham
- Water (e.g. ad libitum): ad libitum; mains water
- Acclimation period: 25 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C):19 - 25 °C
- Humidity (%): 40 - 70 %
- Air changes (per hr): 15 air changes per hour
- Photoperiod (hrs dark / hrs light): 12 hours light and 12 hours darkness

Route of administration:
inhalation: aerosol
Type of inhalation exposure:
head only
Vehicle:
clean air
Details on inhalation exposure:
GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: cylindrical anodised aluminium exposure chamber
- Exposure chamber volume: 30 L
- Method of holding animals in test chamber: head-only
- Source and rate of air: The compressed air supply used was from a clean dry filtered source.
- Method of conditioning air: -
- System of generating particulates/aerosols: DeVilbiss model 646 liquid nebulizer generator, dynamic (continuous flow)
- Method of particle size determination: The particle size was determined using a Delron C55 Cascade Impactor, with 5 separation
stages corresponding to maximum mass median aerodynamic diameters of 0.5, 1.0. 2.0. 4.0 and 8 µm. The samples were obtained
hourly, over periods of up to 8 minutes, -during the exposure period.
- Treatment of exhaust air: The atmospheres were filtered, exhausted to the outside of the building and vented.
- Temperature, humidity, pressure in air chamber: The temperature and relative humidity inside the exposure
chamber were measured continuously and recorded at hourly interva1s throughout th'e 4-hour exposure peri od, using a
digital thermometer with remote probe located in the chamber and a paper hygrometer located in the exhaust duct of the chamber.

TEST ATMOSPHERE
- Brief description of analytical method used: The concentration of the test article was determined gravimetrically. The atmosphere
was sampled by drawing a known volume through an open face glass fibre filter positioned at a site representative of that
occupied by the external nares of the experimental animals.
- Samples taken from breathing zone: yes



TEST ATMOSPHERE (if not tabulated)
- Particle size distribution:
- MMAD (Mass median aerodynamic diameter) / GSD (Geometric st. dev.):

Analytical verification of test atmosphere concentrations:
yes
Duration of exposure:
4 h
Concentrations:
0.513, 2.118, 4.585 and 6.518 mg/L
No. of animals per sex per dose:
5 aminals per sex per group
Control animals:
yes
Details on study design:
- Duration of observation period following administration: 14 days
- Frequency of observations and weighing: twice daily for dead or moribund. The body weight of each animal was recorded immediately before and
after exposure, on days 8 and 15 of the study and at necropsy.
- Necropsy of survivors performed: yes
- Other examinations performed: clinical signs, body weight,organ weights, histopathology, other:
Clinical signs were observed at hourly intervals during the exposure period, then for the remainder of the working day, and once daily thereafter for
14 days.
Necropsy: A full internal and external examination was made under the general supervision of a pathologist. The nasal passages were examined and
an assessment made of any irritation of the respiratory tract.
Organ weights: The lungs, bronchi and trachea were dissected free from fat and other contiguous tissue and weighed together.
Histology: Samples of all gross lesions were fixed in 10% neutral buffered formalin and retained without further processing.
Statistics:
The median lethal concentrations (LC50) together·with 95% fiducial limits were calculated separately for males and females, and for
sexes combined, from the recorded mortality rate using a probit analysis method (Finney, D.J. (971)
Probit Analysis, 3rd ed., Cambridge University Press).
,I
,I
Sex:
female
Dose descriptor:
LC50
Effect level:
3.181 mg/L air (analytical)
Based on:
test mat.
95% CL:
0.567 - 50.411
Exp. duration:
4 h
Sex:
male
Dose descriptor:
LC50
Effect level:
7.655 mg/L air (analytical)
Based on:
test mat.
Exp. duration:
4 h
Sex:
male/female
Dose descriptor:
LC50
Effect level:
5.319 mg/L air (analytical)
Based on:
test mat.
95% CL:
2.981 - 34.296
Exp. duration:
4 h
Mortality:
Qveral-l there was a positive correlation between mortality and chamber concentration. As the minimum level at which death
occurred was 4.585 mg/l for males and 2.118 mg/l for females, the possibility of a sex difference cannot be eliminated.
One male in group 5 died during exposure. Except for one death on day four all deaths occurred on days one or two of the study.
Seven animals were killed for humane reasons on day one. Five of these decedents were in moribund condition.
Clinical signs:
Marked signs of toxicity were observed at 4.585 and 6.518 mg/L immediately after exposure. The signs included ataxia,
occasionally prostration and irregular respiration. and convulsion and signs of ejaculation at 4.585 mg/l. During and/or following
exposure, a variety of other clinical signs were observed at all dose levels, such as chromodacryorrhoea and staining of the fur.
Except for some minor persistent signs such as piloerection, fur staining or occasional injuries to the forefeet, recovery was
complete by day four of the study.
Body weight:
Body weight losses occurred as a result of the r~straint procedures in test and control groups. The losses tended to be greater in
treated groups and persisted in a few individuals until day 8 of the study. However, overall there was no marked effect on body
weight.
Gross pathology:
Mean absolute and relative lung weights at termination for treated groups tended to be slightly higher than the corresponding control va1ues. but all values fell withi n the normal range and the numerical differences were too small to conclude there was a treatment-related effect.
Occasional lung weights for decedents were near or ablove the upper limits of the normal range.
This was probably due to agonal congestive changes.
Animals surviving to termination showed only incidental changes. Some decedents were unremarkable but others had discoloured and
inflated lungs suggestive of acute effects on the cardiopulmonary system. Four of the flve group 3 females had sore forefeet
possible due to self-inflicted trauma.
Interpretation of results:
Toxicity Category IV
Remarks:
Migrated information Criteria used for interpretation of results: other: CLP, EU GHS (Regulation (EC) No. 1272/2008)
Conclusions:
Based on the LC50 female of 3.181 mg/L air the test substance has to be classified according to CLP, EU GHS (Regulation (EC) No. 1272/2008) in Toxicity Category IV.
Executive summary:

In an acute inhalation toxicity study performed according to OECD Guideline 403 5 young Sprague-Dawley rats per sex per group were exposed at single chamber concentrations of 0.513, 2.118, 4.585 and 6.518 mg/L of Guanidine hydrochloride (98.5 % a.i.) by inhalation (head-only) over a period of 4 hours. Corresponding nominal concentrations were in the range 2.124 to 15.280 mg/L. The mass median aerodynamic diameters of the particles in the atmospheres fell in the range 1.88 to 5.62 µm. The aerosol for animal exposures was prepared from an aqueous solution of the test article. A similar group of 5 males and 5 females was exposed to filtered air as a control. Animals then were observed for 14 days.

The acute inhalation median lethal concentrations, calculated by a probit method, were:

LC50 combined: 5.319 mg/L

LC50 Males: 7.655 mg/L

LC50 Females: 3.181 mg/L

Deaths occurred in males at a level of 4.585 mg/l and above, and in females at a level of 2.118 mg/l and above. Overall there was a dose-related relationship between mortality and chamber concentration. Nearly all deaths occurred on days one or two of the study. Marked clinical signs were first observed on the day of exposure. The signs included ataxia and occasionally prostration, irregular respiration, convulsion and signs of ejaculation. A few individuals showed body weight loss that persisted one week after treatment, but overall there was no marked treatment related effect on body weight.

There was no evidence of a treatment-related, effect on lung weight in survivors. Occasional increases in lung weights in decedents were probably due to agonal congestive changes. Animals surviving to termination were unremarkable macroscopically. A few decedents had discolored and inflated lungs.

Endpoint conclusion
Endpoint conclusion:
adverse effect observed
Dose descriptor:
LC50
3 181 mg/m³
Quality of whole database:
The key study is GLP compliant and of high quality (RL 1).

Acute toxicity: via dermal route

Link to relevant study records
Reference
Endpoint:
acute toxicity: dermal
Type of information:
experimental study
Adequacy of study:
key study
Study period:
1984-05-18 to 1984-08-01
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Test procedure according to national (US) standard, which is comparable to OECD guideline
Qualifier:
according to
Guideline:
other: EPA TS-792 Acute exposure, dermal toxicity. Health effects test guidelines, EPA, August 1982; EPA 560/6-82-001
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 402 (Acute Dermal Toxicity)
Deviations:
no
GLP compliance:
yes
Test type:
standard acute method
Limit test:
yes
Species:
rabbit
Strain:
New Zealand White
Sex:
male/female
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Elkhorn Rabbitry, 5265 Starr Way, Watsonville, CA 95076
- Age at study initiation: young adults
- Weight at study initiation: 2.8 to 3.7 kg
- Housing: individually
- Diet (e.g. ad libitum): 150 g of Certified Purina Chow Diet 5322
- Water (e.g. ad libitum): ad libitum
- Acclimation period: 25 d (quarantine, acclimation)

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 17 to 24°C
- Humidity (%): 46 to 74%, except for spikes up to 94% during cleaning
- Air changes (per hr): no data
- Photoperiod (hrs dark / hrs light): 12/12
Type of coverage:
occlusive
Vehicle:
physiological saline
Details on dermal exposure:
TEST SITE
- Area of exposure: 240 cm²
the substance was applied on gauze dressing, taped with hypoallergenic tape (Durapore) and wrapped with bandage (Vetrap)

REMOVAL OF TEST SUBSTANCE
- Washing (if done): yes
- Time after start of exposure: after 24 h

TEST MATERIAL
- Amount(s) applied (volume or weight with unit): 2000 mg/kg bw
- For solids, paste formed: yes, 0.9% saline

Duration of exposure:
24 h
Doses:
2000 mg/kg bw
No. of animals per sex per dose:
5
Control animals:
no
Details on study design:
- Duration of observation period following administration: 14 days
- Frequency of observations and weighing: clinical signs and mortality daily; dermal reactions 0.5, 24, 48, 74 h after removal of the patches; body weights were recorded 7 times during test period
- Necropsy of survivors performed: yes
- Other examinations performed: skin from exposed area was examined microscopically
Sex:
male/female
Dose descriptor:
LD50
Effect level:
> 2 000 mg/kg bw
Based on:
test mat.
Mortality:
no mortality occurred
Clinical signs:
systemic:
- no substance-related clinical signs
local (dermal):
- erythema was observed in all rabbits 30 min after patch removal; 24 h after patch removal the erythema had disappeared in five animals
- slight erythema, necrosis and ulceration was observed in one animal after 72 h
- loss of hair from the patch site or alopecia was observed in 9/10 animals
- bruising was observed in 3/5 females, this had resolved between 48 and 72 h after patch removal
- burns and slight edema were observed in 2/5 males 30 min after patch removal; the edema resolved by 24 h after patch removal, while the burns were still present after 72 h
- necrosis was present in one male 30 min after patch removal; this lesion was observed throughout the 14-day observation period during which time it was characterised by eschar formation
Body weight:
- no substance-related effects
Gross pathology:
- epidermal ulceration covered by a fibrinocellular exudate in one male with necrosis and eschar formation
- no other gross findings
Interpretation of results:
not classified
Remarks:
Migrated information Criteria used for interpretation of results: other: CLP, EU GHS (Regulation (EC) No 1272/2008)
Conclusions:
The dermal LD50 of Guanidine hydrochloride in rabbits was > 2000 mg/kg bw.
Executive summary:

In an acute dermal toxicity study similar to OECD guideline 402 groups of 5 young adult New Zealand White rabbits/sex were dermally exposed to Guanidine hydrochloride (98% pure) moistened with 0.9% saline for 24 h to 240 cm² body surface area at a limit dose of  2000  mg/kg bw using occlusive dressing.  Animals then were observed for 14 days.

No mortality occurred. No substance-related systemic effects were observed. Exposure to the test substance caused dermal irritation and eschar formation.

Dermal LD50 > 2000 mg/kg bw.

Endpoint conclusion
Endpoint conclusion:
no adverse effect observed
Dose descriptor:
LD50
2 000 mg/kg bw
Quality of whole database:
The key study is GLP compliant and of high quality (RL 1).

Additional information

Acute toxicity data on Guanidine hydrochloride are available for the oral, inhalation and dermal route.

Acute oral toxicity

In an acute oral toxicity study similar to OECD guideline 401, groups of fasted Sprague-Dawley rats (9/sex) were given a single oral dose of Guanidine hydrochloride (>98% purity, 61.8% base equivalent Guanidine) in water at doses of 0, 278, 360, 464, 600 and 775 mg/kg bw (expressed as active ingredient Guanidine base), corresponding to 0, 453.14, 756.32, 978, 1263.25 mg/kg bw Guanidine hydrochloride and observed for 14 days.

No mortality occurred in the lowest dose group. 0/9 males, 2/8 females in the 360 mg/kg bw dose group died; 2/9 males, 5/9 females in the 464 mg/kg bw dose group; 5/9 males, 4/7 females in the 600 mg/kg bw dose group and 9/9 males, 9/9 females in the 775 mg/kg bw dose group. Reduced total numbers are due to misdosing; those animals were removed from the study.

Clinical signs were observed in the CNS (increased startle reflex, hyperactivity, and disorientation) and in the gastro-intestinal tract (hunched posture, increased salivation with some staining of the muzzle, and diarrhea) in all dose groups. However, there were no microscopic findings in cerebrum, brainstem and cerebellum of animals with CNS symptoms.

Gross pathology revealed black/serosanguinous material in the stomach, focal depression in the glandular mucosa of the stomach, black and diffuse red areas in the glandular mucosa of the stomach, black and tarry material in the intestine, black and tarry feces.

In the surviving animals no test compound-related gross lesions were reported.

Several rats exhibited central nervous system (CNS) signs. Some rats that exhibited CNS signs died and some others survived. The cerebrum, brainstem and cerebellum of 4 animals died were examined by light microscopy and no lesions were observed.

Oral LD50 Males = 556.5 mg Guanidine/kg bw (95% C.I. 492.3 - 630.9 mg/kg bw)

Oral LD50 Females = 474.6 mg Guanidine/kg bw (95% C.I. 402 - 562.7 mg/kg bw)

corresponding to:

LD50 males = 907.1 mg/kg bw (95% c.i. 802.45 - 1028.4)

LD50 females = 773.6 mg/kg bw (95% c.i 655.3 - 917.2) expressed as Guanidine hydrochloride.

This is supported by two further oral toxicity studies with Guanidine hydrochloride in mice and rats, respectively:

The oral LD50 for Guanidine base in mice was 570.8 mg/kg bw (95% c.i. 491 - 694 mg/kg bw) in males and 612 mg/kg bw (95% c.i. 492 – 1183 mg/kg bw) in females, corresponding to 930.4 mg/kg bw (95% c.i. 800.33 - 1131.22 mg/kg bw) in males and 997.56 mg/kg bw (95% c.i. 801.96 - 1928.29 mg/kg bw) in females expressed as Guanidine hydrochloride.

The oral LD50 for Guanidine hydrochloride in rats was 1120 mg/kg bw (95% c.i. 991 – 1266 mg/kg bw).

Acute inhalation toxicity

In an acute inhalation toxicity study performed according to OECD Guideline 403, 5 young Sprague-Dawley rats per sex per group were exposed at single chamber concentrations of 0.513, 2.118, 4.585 and 6.518 mg/L of Guanidine hydrochloride (98.5 % a.i.) by inhalation (head-only) over a period of 4 hours. Corresponding nominal concentrations were in the range 2.124 to 15.280 mg/L. The mass median aerodynamic diameters of the particles in the atmospheres fell in the range 1.88 to 5.62 µm. The aerosol for animal exposures was prepared from an aqueous solution of the test article. A similar group of 5 males and 5 females was exposed to filtered air as a control. Animals then were observed for 14 days.

The acute inhalation median lethal concentrations, calculated by a probit method, were:

LC50 combined: 5.319 mg/L (5319 mg/m³)

LC50 Males: 7.655 mg/L (7655 mg/m³)

LC50 Females: 3.181 mg/L (3181 mg/m³)

Deaths occurred in males at a level of 4.585 mg/L and above, and in females at a level of 2.118 mg/L and above. Overall there was a dose-related relationship between mortality and chamber concentration. Nearly all deaths occurred on days one or two of the study. Marked clinical signs were first observed on the day of exposure. The signs included ataxia and occasionally prostration, irregular respiration, convulsion and signs of ejaculation. A few individuals showed body weight loss that persisted one week after treatment, but overall there was no marked treatment related effect on body weight.

There was no evidence of a treatment-related, effect on lung weight in survivors. Occasional increases in lung weights in decedents were probably due to agonal congestive changes. Animals surviving to termination were unremarkable macroscopically. A few decedents had discoloured and inflated lungs.

Acute dermal toxicity

In an acute dermal toxicity study similar to OECD guideline 402 groups of 5 young adult New Zealand White rabbits/sex were dermally exposed to Guanidine hydrochloride (98% pure) moistened with 0.9% saline for 24 h to 240 cm² body surface area at a limit dose of 2000 mg/kg bw using occlusive dressing. Animals then were observed for 14 days.

No mortality occurred. No substance-related systemic effects were observed. Exposure to the test substance caused dermal irritation and eschar formation.

Dermal LD50 > 2000 mg/kg bw Guanidine hydrochloride.


Justification for selection of acute toxicity – oral endpoint
The study with the most critical results has been selected as key study. This study is supported by two studies with similar results.

Justification for selection of acute toxicity – inhalation endpoint
Only one key study available

Justification for selection of acute toxicity – dermal endpoint
Only one key study available

Justification for classification or non-classification

According to CLP, EU GHS (Regulation (EC) No 1272/2008), Guanidine hydrochloride is classified with Hazard Category 4 for acute oral toxicity (harmful if swallowed) since the results obtained in all available studies are conclusive, and LD50 values are in the range from 773.6 to 1120 mg/kg bw.

The findings from acute oral toxicity studies suggest that the guanidine ion exhibits primary effects on the central nervous system / neuromuscular system. However, effects were observed in the range of classification Hazard Category 4, therefore on the basis of available data no additional classification for STOT-SE is considered necessary.

Guanidine hydrochloride is classified for acute inhalation toxicity (harmful if inhaled) with Hazard Category 4 since the lowest obtained LC50 from an acute inhalation study was 3.181 mg/L for female rats.

Guanidine hydrochloride is not classified for acute dermal toxicity since the LD50 value is > 2000 mg/kg bw.

Guanidine hydrochloride is labelled with R20/22 according to Directive 67/548 EEC. According to CLP, EU GHS (Regulation (EC) No 1272/2008), labelling with H302/332 is required.