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After oral administration, beta-Cyclodextrin is slightly toxic in a 52 weeks repeated dose toxicity test with a NOAEL of 12500 ppm of beta-cyclodextrin which is equivalent to 650 mg/kg bw/day for males and 860 mg/kg bw/day for female rats.

Key value for chemical safety assessment

Repeated dose toxicity: via oral route - systemic effects

Endpoint conclusion
Dose descriptor:
NOAEL
650 mg/kg bw/day

Additional information

In a sub-acute (4-wk) feeding study performed according to OECD Guideline 407, the toxicity of beta-cyclodextrin was examined by administering the test substance at a five percent level in the diet to Wistar rats (4200 mg/kg bw males; 4160 mg/kg bw for females). The substance was mixed with the diet without an analytical verification. Clinical observations, growth, food and water intake, haematology, clinical chemistry, urinalysis, organ weights , macroscopic examination, and microscopic examination of the liver, kidneys, heart, adrenals, spleen, caecum and mesenteric lymph nodes were used as criteria for disclosing possible harmful effects.

 The ingestion of beta-cyclodextrin by rats for a period of 4 weeks in the present study was accompanied by a number of changes. Slight caecal enlargement occurred in males and females fed 5% beta-Cyclodextrin. Many other poorly digestible carbohydrates (e.g. chemically modified starches, lactose) tend to induce caecal enlargement . The phenomenon is ascribed to an increased load of osmotically active substances (such as volatile fatty acids or lactic acid) in the large intestine, arising from microbial fermentation of carbohydrates that were incompletely digested or absorbed in the small intestine. It is known from the literature that cyclodextrins are not absorbed from the stomach and the small intestine, while the microflora of the large intestine has an important part in the metabolism of cyclodextrins. In the present study, microbiological degradation of unabsorbed beta-Cyclodextrin may explain the observed distention of the caecum, the swollen bellies, the increased water intake and the diarrhoea observed at levels of 5% beta-cyclodextrin.

The above intestinal changes are not deemed to be of toxicological significance but are rather adaptation phenomena. The relatively low plasma urea concentrations in rats fed 5% beta-cyclodextrin, are ascribed to increased microbial activity as well. In the rat, blood urea is related to the ammonia levels in the caecum. Bacteria may utilise ammonia nitrogen (derived from the hydrolysis of urea) for protein synthesis. As a result of increased bacterial population, less ammonia is reabsorbed to be reconverted to urea in the liver. This may result in lower blood urea levels. Therefore no toxicological significance is attached to this finding.

It is not clear from the present study whether the other changes in clinical chemistry variables in rats fed 5% beta-cyclodextrin are of toxicological significance, or whether they represent reversible adaptive responses associated with the ingestion of large quantities of a poorly digestible carbohydrate. Diarrhoea was observed already on the first day of the study. From day 7 the rats apparently adapted to the feeding of beta-cyclodextrin since the signs of diarrhoea disappeared. In rats fed 5% beta-cyclodextrin a few changes in haematology or clinical chemistry variables were observed which were generally slight and possibly of doubtful toxicological significance. As a result and since all other changes were only slight and/or reversible within the study period, the NOAEL for both sexes is set to be > 4160 mg/kg bw.

 

A subchronic (13 weeks) toxicity of beta-cyclodextrin was carried out in Sprague-Dawley rats according to OECD Guideline 408. Six groups of animals each comprising 20 males and 20 females were used. The test substance was incorporaled into the semi-synthetic diet in place of the equivalent fraction of starch (by weight). at doses of 0, 1.25, 2.5, 5 and 10 % respectively. The last group constituted received a diet containing 10 % lactose incorporated in the feed as for the other groups. The substance was stable during the course of this test as was shown by HPLC analysis at the beginning and the end of the study.

The animal behaviour, body weight, food and water consumption were not modified by the treatment. Ophthalmological examinations disclosed no treatment-induced changes. Macroscopical examinations performed at necropsy, histopathological and histochemical examination, revealed no lesions or functional modification attributable to treatment. The only treatment-related modification was an increase In the caecal weight in both sexes, also observed in the group treated with lactose. This is an observation commonly described in rats receiving fermentable carbohydrates which are not completely digested in the smaII intestine. One biochemical parameter, the plasma triglyceride level was significantly decreased, in a dose-related manner, in all male animals receiving beta-cyclodextrin. No other modifications attributable to treatment were observed in plasma or urine parameter examined. The few variations were within normal biological limits for the species used. The same applies to the hematological parameters. In conclusion, administration of beta-Cyclodextrin to Sprague-Dawlev rats for 13 weeks did not induce any modification or anomalv indicative of a toxic effect.

 

Groups of 17 (19 at the highest dose) male and female Sprague-Dawley rats, 4 weeks old at commencement of the study, were given beta-cyclodextrin by gavage in aqueous suspension at daily dose levels of 0, 100, 400 or 1 600 mg/kg bw After 3 months administration an interim sacrifice was made as follows: Control, 5 males & 4 females; 100 mg/kg bw/d group, 3 males & 5 females; 400 mg/kg bw/d group, 5 males & 4 females; 1600 mg/kg bw/d group, 2 males & 4 females. The remaining animals were maintained on the same dosing regime to 6 months. Food and water intake and body weights were determined weekly. At termination, urinalysis (pH, protein, glucose, ketone bodies, blood, bilirubin, urobilinogen) was carried out on 5 animals of each sex in each group; haematological (RBC, WBC, haemoglobin and haematocrit) and serum biochemical analyses (protein, albumin/globulin, GOT, GPT, Alk-P-ase, BUN, bilirubin, total cholesterol and glucose) were carried out on all survivors. At autopsy, the following organs were weighed: brain, pituitary, thyroid, thymus, heart, lung, liver, kidneys, adrenals, spleen, pancreas, testes or ovaries; these organs and stomach and intestinal tract were examined histologically (haematoxylin & eosin).

A total of 18 animals died during the study as follows: 100 mg/kg bw/d, 3 males; 400 mg/kg bw/d, 2 females; and 1600 mg/kg bw/d, 6 males and 7 females. It was claimed that these deaths were due to misdosing, as no abnormalities were detected other than "pneumonia-like" lung pathology. There was a small decrement of weight gain of both sexes in the top-dose group only, otherwise weight gain, food and water intake were similar to controls and there were no treatment-related effects on organ weights, urinalysis or haematological parameters. Serum biochemical indices generally were within the normal range although some significant differences from controls were observed, notably a dose-related increase in alk-P-ase in males and a decrease in blood glucose in females of the top two dose groups. Gross and histopathological examination did not reveal any treatment-related abnormalities. If the deficit in weight gain at the top-dose level is considered an adverse effect in the absence of other, pathological, changes, the NOAEL for this study is 400 mg/kg bw/day by gavage.

The toxicity of Beta-cyclodextrine was assessed in the dog following its administration in the diet at levels of 0 (Control), 10000. 25000 and 50000 ppm for 52 weeks according to a guideline equivalent to OECD guideline 452. 4 dogs per sex and dose group were used for this study which were administered daily. There were no deaths and no clinical signs considered to be related to treatment. There was no effect of treatment on the bodyweight or bodyweight gain of the dogs. There was no effect of treatment on food consumption. There were no treatment-related changes on the eyes of the animals. There were no changes in hematology and biochemistry considered to be of toxicological importance. At dietary inclusion levels of 25000 and 50000 ppm there was a trend for increased urinary protein concentrations for males and females. There were no treatment-related changes seen in the bone marrow examination. Also no effect of treatment was seen on organ weights or at macroscopic post mortem evaluations. There were no treatment-related findings seen in histology. It is concluded that the level of 50000 ppm represents the no observed adverse effect level (NOAEL) in this study.

In the key study, Beta-cyclodextrin was assessed for its toxicity to dogs by repeated dietary administration over a period of 52 weeks. Thirty-two pure-bred beagle dogs were divided into 4 groups, each containing 4 males and 4 females. Three groups received the test substance, Beta-eyclodextrin, by inclusion in the daily diet at levels of 6200, 12500 or 50000 ppm for 52 weeks. The fourth group received untreated basal diet and acted as controls. Clinical signs, bodyweight and food consumption were monitored throughout the study. Ophthalmoscopy and laboratory investigations were performed at intervals. On completion of 52 weeks treatment, the animals were killed; a bone marrow smear was taken, macroscopic examination of all tissues was performed, organ weights were recorded and an extensive list of tissues was processed and examined microscopically. The following comments in relation to the principal findings during the study are made in summary. There were no unscheduled deaths. There was a slightly higher incidence of intermittent liquid faeces in animals receiving Beta-cyclodextrin compared to concurrent controls but no dosage relationship was apparent and overall incidences were low. There were no other signs considered to be related to treatment. Bodyweight and food consumption showed no conclusive effects of treatment. For ophthalmoscopy all changes were considered spontaneous in origin and unrelated to treatment. There ·was no conclusive effect of treatment for haematology and biochemistry. At Weeks 13, 26, 39 and 52, group mean urinary protein levels were increased for males and slightly increased for females receiving 50000 ppm. The majority of protein was found to be the globulin fractions. Group mean urinary calcium levels were increased at 50000 ppm in Weeks 13, 26 and 39 particularly for males. At Week 52, calcium values for males only were increased at 50000 ppm. In the additional analyses performed at Week 52 only, 1 male receiving 12500 ppm and the majority receiving 50000 ppm showed slightly increased GGT .levels. Group mean NAG levels were also considered to be slightly increased for males receiving 12500 or 50000 ppm, though not in a dosage related fashion. There were no other noteworthy findings. All marrow smears were considered normal. Minor intergroup differences in organ weights and pathological findings were considered ·to be spontaneous in origin and unrelated to treatment. A marginally higher incidence of liquid faeces was noted in treated groups, but overall incidences were so low as to be considered of no toxicological importance. Urinary protein (particularly globulin) and urinary calcium levels were increased at 50000 ppm, and slightly increased urinary GOT and NAG levels were noted at 12500 and 50000 ppm. In the absence of pathological changes considered to be related to treatment, it is concluded that administration of beta-cyclodextrin to dogs by dietary inclusion at levels of up to 50000 ppm for 1 year produced no clear signs of systemic toxicity.

Three groups of 20 male and 20 female Crl:CD (SD) BR rats received beta-cyclodextrin (>= 99 % pure), by dietary administration at dosages of 12500, 25000 or 50000 ppm for 52 weeks. A similarly sized group received untreated diet and acted as controls. The objective of the study was to assess the chronic toxicity of beta-cyclodextrin. Clinical signs, bodyweights and food consumption were monitored throughout the treatment period. Ophthalmoscopic, haematological, biochemical and urinalysis investigations were performed pre-treatment and in Weeks 13, 26, 39 and 52. Organ weights were obtained; macroscopic and microscopic pathological examinations were also performed. Urine and faeces samples were collected in Weeks 13 and 52 for pharmacokinetic analyses; serum samples were obtained pre-treatment and in Weeks 13, 26 and 52 for vitamins A, D and E analysis,. and liver samples were obtained at termination for analysis of vitamins A and E. Dietary administration of beta-cyclodextrin to rats at dosages of 12500, 25000 or 50000 ppm for 52 weeks revealed no effects on mortality, clinical signs, bodyweight gains, efficiency of food utilisation, ophthalmoscopic findings, haematological and urine analysis investigations, organ weights or or macroscopic pathology.

The liver was shown to be the target organ for toxicity with the following changes noted histopathologically: an increased incidence in single cell necrosis, portal inflammatory cell infiltration and focal basophilic hepatocytes in males and/or females receiving 50000 or 25000 ppm, and an increased incidence in centrilobular hepatocyte enlargement and prominent sinusoidal lining cells/leucocytosis in males and/or females receiving 50000 ppm. These hepatic lesions were consistent with the increase in the liver enzymes GPT, GOT and OCT noted biochemically for males and/or females receiving 50000 or 25000 ppm, and the reduction in triglycerides noted for both sexes receiving 50000 ppm, with males appearing to be more affected. than females. Although a slight increase in GPT and GOT was noted for males receiving 12500 ppm in Week 52, no hepatic lesions were noted histopathologically, and as a level of statistical significance was attained for GPT only these findings at this dosage are considered not be of toxicological importance. Beta-cyclodextrin at a dosage of 50000 ppm was also noted to exacerbate the background incidence of area/foci of hepatocytes with rarefied cytoplasm. In addition in the kidney an increased incidence of minimal/trace amounts of pigment in the epithelium of the cortical tubules was noted histopathologically in females receiving 50000 or 25000 ppm. In conclusion, the non-toxic dosage level based on the results in this study is considered to be 12500 ppm of beta-cyclodextrin which is equivalent to 650 mg/kg bw/day for males and 860 mg/kg bw/day for female rats.


Repeated dose toxicity: via oral route - systemic effects (target organ) digestive: liver; urogenital: kidneys

Justification for classification or non-classification