Dilactide

Endpoint summary

Description of key information

Lactide (18:1 mixture of L-lactide and m-lactide) was tested in dogs in a 2 week dose range finding study and a subsequent 90d full study similar to OECD 408. The primary toxic effect was irritation of the gastrointestinal tract at 100 mg/kg/d in the 90d study. Lactide is a suitable read across partner as dilactide is a mixture of D- and L-lactide isomers.

Key value for chemical safety assessment

Repeated dose toxicity: via oral route - systemic effects

Link to relevant study records

Reference

Endpoint:

sub-chronic toxicity: oral

Type of information:

migrated information: read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Published study, meets generally accepted scientific standards and is described in sufficient detail. L-lactide is a suitable read across partner as dilactide is a mixture of D- and L-lactide isomers.

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 409 (Repeated Dose 90-Day Oral Toxicity Study in Non-Rodents)

Deviations:

not specified

Principles of method if other than guideline:

Doses for the 13-wk study were selected based on the results of a 2-week study. In the 13-wk study, four dogs per sex were assigned to each of four treatment groups (dosed with lactide at 0, 4, 20 and 100 mg/kg body weight/day). Each dog received daily oral doses of one to six gelatin capsules containing lactide. Doses were administered at approximately 1 hr after feed was withdrawn, and at approximately the same time each day for 13 weeks. Control dogs received the same number of empty capsules as dogs of the corresponding sex in the highest dose group. Doses were calculated based on the body weight of each dog during the previous week.

GLP compliance:

not specified

Limit test:

no

Species:

dog

Strain:

Beagle

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Harlan Sprague Dawley, Inc ( Madison, WI, USA)
- Age at study initiation: ranged from 5 to 10 months
- Fasting period before study: 1 hour before dosing
- Housing: individual housed in stainless-stell cages on racks and were exercised at least twice weekly throughout the quarantine and study period
- Diet (e.g. ad libitum): dogs were fed Certified Canine Chow 5007 (PMI Feeds, Inc) for approximately 2 hours each day
- Water (e.g. ad libitum): ad libitum
- Acclimation period: at least 2 weeks

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 20 - 26°C
- Humidity (%): 35 - 85%
- Photoperiod (hrs dark / hrs light): 12/12

Route of administration:

oral: capsule

Vehicle:

unchanged (no vehicle)

Details on oral exposure:

Each dog received daily oral doses of one to six gelatin capsules containing lactide. Doses were administered at approximately 1 h after feed was withdrawn, and at approximately the same time each day for 13 weeks.
Control dogs received the same number of empty capsules as dogs of the corresponding sex in the highest dose group. Doses were calculated based on the body weight of each dog during the previous week.

Analytical verification of doses or concentrations:

not specified

Duration of treatment / exposure:

13 weeks

Frequency of treatment:

SIngle daily dose

Remarks:

Doses / Concentrations:
0, 4, 20, 100 mg/kg bw/d for 13 weeks.
Basis:
actual ingested

No. of animals per sex per dose:

4

Control animals:

yes, concurrent vehicle

Observations and examinations performed and frequency:

Observations:
- Dogs were observed twice daily for mortality or moribundity.
- Cageside observations were performed daily, approximately 1 h after dosing.
- Once a week, each dog was removed from its cage and examined closely for detailed clinical signs of toxicity.
- Throughout each study:
dogs were weighed weekly, and food consumption was measured once a week over a 2-hour period.

Clinical pathology:
- blood and urine samples were obtained from each dog for clinical pathology and urinalysis determinations during quarantine, during week 5 and 9, and within 3 days prior to terminal sacrifice

Dogs were fasted overnight prior to blood collection for haematologic, clinical chemistry and coagulation analyses

Haematologic analyses included:
total leucocyte count, erythrocyte count, haemaglobin, haematocrit, mean corpuscular volume, mean corpuscular haemoglobin, mean corpuscular haemoglobin concentration, platelet count and differential leucocyte count. Reticulocyte counts and red blood cell morphology were evaluated.

Clinical chemistry analysis included:
By using a Roche Cobas Fara clinical chemistry analyser: blood urea nitrogen, creatinine, serum glucose, serum aspartate aminotransferase, serum alanine aminotransferase, alkaline phosphatase, glutamyl transferase, sodium, potassium, chloride, calcium, inorganic phosphate, total protein, albumin, albumin/total protein ratio, total bilirubin and cholesterol.

Coagulation analyses included:
Prothrombin time and activated partial prothrombin time, fibrinogen

Urine analyses included:
Urine specific gravity, urine microscopic sediment, urine pH, ketones, protein, glucose, bilirubin and occult blood

Sacrifice and pathology:

GROSS PATHOLOGY: Yes
HISTOPATHOLOGY: Yes

Statistics:

- Groups means and standard deviations for: body weights, food consumption, clinical pathology parameters, for terminal body weights and for absolute and relative organ weights
- Body weights, food consumption and clinical pathology parameters were evaluated by two-way repeated ANOVA, and if significant by Dunnett's test
- Mean body weights, mean organ weights and organ/body, organ:brain ratios for each treated group were compared to those of the control group by a two-tailed Student's t-test for each sex

Clinical signs:

effects observed, treatment-related

Description (incidence and severity):

Emesis once in each of two female dogs (one in the 0 mg/kg and one in the 100 mg/kg group during week 9). Bloody diarrhoea was seen once during week 6 in one female dog of the 100 mg/kg group

Mortality:

mortality observed, treatment-related

Description (incidence):

Emesis once in each of two female dogs (one in the 0 mg/kg and one in the 100 mg/kg group during week 9). Bloody diarrhoea was seen once during week 6 in one female dog of the 100 mg/kg group

Body weight and weight changes:

no effects observed

Food consumption and compound intake (if feeding study):

no effects observed

Food efficiency:

not specified

Water consumption and compound intake (if drinking water study):

not specified

Ophthalmological findings:

not specified

Haematological findings:

no effects observed

Clinical biochemistry findings:

no effects observed

Urinalysis findings:

no effects observed

Behaviour (functional findings):

not examined

Organ weight findings including organ / body weight ratios:

no effects observed

Gross pathological findings:

effects observed, treatment-related

Description (incidence and severity):

stomach foci in one male/female from the 100 mg/kg , and one female from the 4mg/kg dose group

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Description (incidence and severity):

moderately severe ulceration of the stomach mucosa seen in one female dog of the high dose group

Histopathological findings: neoplastic:

no effects observed

Dose descriptor:

NOAEL

Remarks:

(systemic)

Effect level:

100 mg/kg bw/day (actual dose received)

Based on:

test mat.

Sex:

male/female

Dose descriptor:

LOAEL

Remarks:

(local)

Effect level:

100 mg/kg bw/day (actual dose received)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: gastrointestinal irritation

Dose descriptor:

NOAEL

Remarks:

(local)

Effect level:

20 mg/kg bw/day (actual dose received)

Based on:

test mat.

Sex:

male/female

Critical effects observed:

not specified

Table 1: Incidence of gross lesions in dogs treated for 13 weeks with oral doses of lactide
Dose group		0 mg/kg	4 mg/kg	20 mg/kg	100 mg/kg
Males
Stomach focus		0	0	0	1
Females
Stomach focus		0	1	0	1

Incidence= number of dogs in a given dose group with a given lesion. n=4 for all dose groups

Conclusions:

Lactide acts primarily, if not only, as an irritant after oral administration. 13 weeks NOAEL is 100 mg/kg bw/d.

Executive summary:

In a subchronic toxicity study lactide (18:1 mixture of l-lactide and m-lactide) was administered to 4 beagle dogs/sex/dose by capsule at dose levels of 4, 20, 100 mg/kg bw/day for 13 weeks.

The only apparent toxic effect at 100 mg/kg/day was gastrointestinal irritation. Therefore, the local LOAEL is 100 mg/kg/d. No systemic effects were reported at 100 mg/kg/d. Thus, the systemic NOAEL for orally administered lactide under the conditions in this study was considered to be 100 mg/kg/day. Lactide is a suitable read across partner as dilactide is a mixture of D- and L-lactide isomers.

This subchronic study in dog is acceptable and satisfies the principle requirement for a subchronic oral study similar to OECD 409 in dog.

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

NOAEL

100 mg/kg bw/day

Study duration:

subchronic

Species:

dog

Repeated dose toxicity: inhalation - systemic effects

Endpoint conclusion

Endpoint conclusion:

no study available

Repeated dose toxicity: inhalation - local effects

Endpoint conclusion

Endpoint conclusion:

no study available

Repeated dose toxicity: dermal - systemic effects

Endpoint conclusion

Endpoint conclusion:

no study available

Repeated dose toxicity: dermal - local effects

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information

Lactide is rapidly hydrolysed to lactic acid in water and in-vivo (gastric acid). Lactic acid is a ubiquitous and essential molecule of life. Lactate is non-toxic, any (local) effects are due to pH effects only.

In addition, in an oral toxicity (dose range finding) study, the read across partner lactide (18:1 mixture of L-lactide and m-lactide) was administered to beagle dogs by capsule at dose levels of 10, 100, 400, 1.000 and 2.500 mg/kg bw/day for 2 weeks, and 0, 4, 20 and 100 mg/kg/d for 13 weeks. The primary toxic effect of lactide in dogs was irritation of the alimentary tract. As irritating effects occurred down to a daily dose of 400 mg/kg bw (for 2 wks), the sub-chronic study was run with a maximum dose of 100 mg/kg bw/d.

At 1.000 and 2.500 mg/kg/d effects on body weight, and absolute and relative organ weights were reported in the 14-day dose range finding study for thymus and spleen. These effects were considered secondary to the irritation of the alimentary tract. In addition, a mild to moderate renal tubular regeneration was reported in all animals of the 2.500 mg/kg/d dose. Regeneration of the renal tubular epithelium is frequently seen as a reparative or adaptive change following tubular epithelial necrosis, and is suggestive of prior damage to this tissue. Although the mechanism of this effect is unknown, lactide toxicity cannot be excluded. Based on the possible renal toxicity the (systemic) LOAEL is 2.500 mg/kg bw/day. That's well above the limit dose of 1.000 mg/kg/d for a sub-acute toxicity study.

No systemic adverse effects were reported at the highest dose tested in the 90 d study (100 mg/kg/d). Therefore, the (systemic) NOAEL for orally administered lactide in a 90-d study in the dog is considered to be 100 mg/kg/day. The primary toxic effect after oral dosing was irritation of the gastrointestinal tract at 100 mg/kg/d. Lactide is a suitable read across partner as dilactide is a mixture of D- and L-lactide isomers.

Justification for selection of repeated dose toxicity via oral route - systemic effects endpoint:
Meets generally accepted scientific standards and is described in sufficient detail

Repeated dose toxicity: via oral route - systemic effects (target organ) digestive: other

Justification for classification or non-classification

Dilactide is to be considered non-toxic; the only effect are due to local irritation in the gastointestinal tract as a consequence of the formation of lacate derivates including lactoyl lactic acid and monomeric lactic acid. Therefore, based on the available data from the read across partner lactide, an 18:1 mixture of L-lactide and m-lactide, Dilactide does not warrant classification for repeated dose toxicity.