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Description of key information

key study: There is a slight dose-related antinociceptive effect for cyanocobalamin at high dose levels in the writhing reaction test. No toxic effects were observed at any dose level tested orally. The NOAEL was determined to be ≥ 5620 mg/kg bw/day.

Key value for chemical safety assessment

Repeated dose toxicity: via oral route - systemic effects

Link to relevant study records
Reference
Endpoint:
repeated dose toxicity: oral
Remarks:
other: 7-days repeated dose toxicity test.
Type of information:
experimental study
Adequacy of study:
supporting study
Reliability:
3 (not reliable)
Rationale for reliability incl. deficiencies:
other: No guideline was followed. Only few parameters were examined.
Principles of method if other than guideline:
The aim of this study was to determine whether oral administration of the test substance given alone or in combination for 7 consecutive days possesses any antinociceptive effect using the mouse-writhing test.
GLP compliance:
not specified
Limit test:
no
Species:
mouse
Strain:
NMRI
Sex:
female
Details on test animals or test system and environmental conditions:
TEST ANIMALS
- Source: Lippische Vesuchstierzucht, Hagemann GmbH & Co, Extertal, FRG.
- Weight at study initiation: 21-28g.
- Diet (e.g. ad libitum): standard mouse diet, ad libitum.
- Water (e.g. ad libitum): ad libitum.
Route of administration:
oral: gavage
Vehicle:
other: hydroxypropyl methylcellulose gel.
Details on oral exposure:
DOSAGE PREPARATION
The test compound was suspended in 0.8% aqueous hydroxypropyl methylcellulose gel.
The test substance was given alone or in combination at a ratio of 1:1:0.0025 for thiamine, pyridoxine, and cyanocobalamin.
Analytical verification of doses or concentrations:
not specified
Duration of treatment / exposure:
7 days
Frequency of treatment:
Daily
Remarks:
Doses / Concentrations:
215, 1000, 5620 mg/kg bw/day (Cyanocobalamin alone)
Basis:
nominal in diet
Remarks:
Doses / Concentrations:
0.27, 1.25, 7.0 mg/kg bw/day (Cyanocobalamin when administered in combination)
Basis:
nominal in diet
Remarks:
Doses / Concentrations:
Induction of the writhing reaction: 10 ml 1% aqueous acetic acid/kg bw.
Basis:
other: intraperitoneal injection.
Control animals:
yes, concurrent vehicle
Details on study design:
- Dose selection rationale: In a preliminary toxicity test a maximum tolerated dose of 5000 mg/kg bw was determined.

Positive control:
None.
Other examinations:
WRITHING REACTIONS: The number of writhing reactions was monitored for 20 minutes after the injection of the acetic acid solution.
Statistics:
A Kruskal-Wallis one-way analysis of variance in conjunction with a Wilcoxon two-sample test was used for the statistical analysis.
Clinical signs:
no effects observed
Mortality:
no mortality observed
Body weight and weight changes:
not examined
Food consumption and compound intake (if feeding study):
not examined
Food efficiency:
not examined
Water consumption and compound intake (if drinking water study):
not examined
Ophthalmological findings:
not examined
Haematological findings:
not examined
Clinical biochemistry findings:
not examined
Urinalysis findings:
not examined
Behaviour (functional findings):
not examined
Organ weight findings including organ / body weight ratios:
not examined
Gross pathological findings:
not examined
Histopathological findings: non-neoplastic:
not examined
Histopathological findings: neoplastic:
not examined
Details on results:
CLINICAL SIGNS AND MORTALITY
No toxic effects were found at any dose level tested.

OTHER FINDINGS
WRITHING REACTIONS: At 5620 mg/kg bw/day, Cyanocobalamin given alone reduced by 18% compared to the control the number of writhing reactions. Cyanocobalamin at a ratio of 1:1:0.0025 (thiamine, pyridoxine, and cyanocobalamin) increased the antinociceptive effect even further reducing the number of writhing reactions by 38 and 50% at 1000 and 5620 mg/kg bw/day (1.25 and 7.0 mg/kg bw/day of Cyanocobalamin, respectively).
Dose descriptor:
LOAEL
Effect level:
5 620 mg/kg bw/day (nominal)
Based on:
test mat.
Sex:
female
Critical effects observed:
not specified
Conclusions:
There is a slight dose-related antinociceptive effect for cyanocobalamin at high dose levels in the writhing reaction and that the addition of cyanocobalamin to the thiamine and pyridoxine combination resulted in a potentiating effect of cyanocobalamin antinociceptive effect. No toxic effects were observed at any dose level tested. The LOAEL was determined to be 5620 mg/kg bw/day.
Executive summary:

A writhing test was performed in order to determine the antinociceptive effects of the test item when administered orally to mice, alone or in combination, for 7 consecutive days. Female mice were exposed to doses of 215, 1000 and 5620 mg/kg bw/day of the cyanocobalamin alone or in combination at a ratio of 1:1:0.0025 for thiamine, pyridoxine, and cyanocobalamin. Control mice received the vehicle. 2h after the last administration a writhing reaction was induced by intraperitoneal injection of 10 ml 1% aqueous acetic acid/kg bw. The number of writhing reactions was monitored for 20 min after the injection in order to assess the antinociceptive effects of the test item. Following repeated oral administration, cyanocobalamin alone exerted a slight antinociceptive effect at 5620 mg/kg bw/day. At this dose level the number of writhing reactions was reduced by 18% compared to the control. Cyanocobalamin at a ratio of 1:1:0.0025 (thiamine, pyridoxine, and cyanocobalamin) increased the antinociceptive effect even further reducing the number of writhing reactions by 38 and 50% at 1000 and 5620 mg/kg bw/day. From the results of the present study it can be concluded that there is a slight dose-related antinociceptive effect for cyanocobalamin at high dose levels in the writhing reaction and that the addition of cyanocobalamin to the thiamine and pyridoxine combination resulted in a potentiating effect of cyanocobalamin antinociceptive effect. No toxic effects were observed at any dose level tested. The LOAEL was determined to be ≥ 5620 mg/kg bw/day.

Endpoint conclusion
Endpoint conclusion:
no adverse effect observed
Dose descriptor:
LOAEL
5 620 mg/kg bw/day
Study duration:
subacute
Species:
mouse

Additional information

Oral route:

Key study: A writhing test was performed by administration of cyanocobalamin oraly to mice for 7 consecutive days. Female mice received 215, 1000 and 5620 mg/kg bw/day. Control mice received the vehicle. 2h after the last administration a writhing reaction was induced by intraperitoneal injection of 10 ml 1% aqueous acetic acid/kg bw and the animals were monitored for 20 minutes. Following repeated oral administration, cyanocobalamin exerted a slight antinociceptive effect at 5620 mg/kg bw/day. At this dose level the number of writhing reactions was reduced by 18% compared to the control. From the results of the present study it can be concluded that there is a slight dose-related antinociceptive effect for cyanocobalamin at high dose levels in the writhing reaction. No toxic effects were observed at any dose level tested. The LOAEL was determined to be ≥ 5620 mg/kg bw/day.


Justification for selection of repeated dose toxicity via oral route - systemic effects endpoint:
Only study available.

Justification for classification or non-classification

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