Phenacetin

Developmental toxicity / teratogenicity

Administrative data

Endpoint:

developmental toxicity

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1965

Materials and methods

Principles of method if other than guideline:

- Principle of test: Oral administration of phenacetin at doses of 150, 300, 600 and1200 mg/kg bw/d from gestational days 0 to 20

GLP compliance:

not specified

Test material

Test material information

Constituent 1

Reference substance name:

Phenacetin

EC Number:

200-533-0

EC Name:

Phenacetin

Cas Number:

62-44-2

Molecular formula:

C10H13NO2

IUPAC Name:

phenacetin

Test animals

Species:

rat

Strain:

Sprague-Dawley

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source:
- Age at study initiation:
- Weight at study initiation: 160-180 g.
- Diet (e.g. ad libitum): Altromin®-PreBlinge
- Water (e.g. ad libitum): ad libitum

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22ºC

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

other: Wheat starch

Details on exposure:

PREPARATION OF DOSING SOLUTIONS:

VEHICLE
- Concentration in vehicle: 3-12 % (test item)

Analytical verification of doses or concentrations:

no

Details on mating procedure:

Vaginal swabs were taken regularly in the morning at leat 14 days before the first mating attempt until necropsy on the 21st day of pregnancy. after the onset of prooestrus, the animals were mated overnight and after a positive sperm result, they were removed for treatment. Of a total of 160 females, 149 mated within 2 months, the remaning females were not considered.

Duration of treatment / exposure:

From gestional days 0 to 20.

Frequency of treatment:

Daily

Doses / concentrations

Doses / concentrations 1

Dose / conc.:

0 mg/kg bw/day

Doses / concentrations 2

Dose / conc.:

150 mg/kg bw/day

Doses / concentrations 3

Dose / conc.:

300 mg/kg bw/day

Doses / concentrations 4

Dose / conc.:

600 mg/kg bw/day

Doses / concentrations 5

Dose / conc.:

1 200 mg/kg bw/day

No. of animals per sex per dose:

Females: control animals (n=40); 150 mg/kg (n=20); 300 mg/kg (n=20); 600 mg/kg (n=20); 1200 mg/kg (n=20).

Control animals:

yes

Examinations

Maternal examinations:

Vaginal swabs

Ovaries and uterine content:

The ovaries and uterine content was examined after termination: Yes

Blood sampling:

Hemoglobin concentrations in blood

Fetal examinations:

Survival rate, fate, developmental status (size, weight, formation) and macroscopically fetal malformations, skeleton

Results and discussion

Results: maternal animals

General toxicity (maternal animals)

Clinical signs:

not specified

Dermal irritation (if dermal study):

not examined

Mortality:

mortality observed, treatment-related

Description (incidence):

2 non gravid animal died after 16 days of feeding under 1200 mg/kg. The reason for this could be among other things, a reduced receptivity of the uterine mucosa as a result of a toxic damage to the mother.

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

The increase in weight of the mothers during the test was only achieved by the highest phenacetin dose.

Food consumption and compound intake (if feeding study):

effects observed, treatment-related

Description (incidence and severity):

The consumption of these animals was more than that of the control group.

Food efficiency:

not examined

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

not examined

Ophthalmological findings:

not examined

Haematological findings:

no effects observed

Description (incidence and severity):

The result of test item and hemoglobine concentrations in the blood suggest a relatively slow rate of absorption and elimination with strong individual variations.

Clinical biochemistry findings:

not examined

Endocrine findings:

not examined

Urinalysis findings:

not examined

Behaviour (functional findings):

not examined

Immunological findings:

not examined

Organ weight findings including organ / body weight ratios:

no effects observed

Description (incidence and severity):

There was no discernible influence on the placental weight.

Gross pathological findings:

not examined

Neuropathological findings:

not examined

Histopathological findings: non-neoplastic:

not examined

Histopathological findings: neoplastic:

not examined

Other effects:

not specified

Maternal developmental toxicity

Pre- and post-implantation loss:

no effects observed

Description (incidence and severity):

In the case of proven gravidity, the number of implantations per dam was unaffected by phenacetin. It only resulted in a slight increase in the intrauterine mortality rate, which only increased sharply after administration of 1200 mg/kg.

Total litter losses by resorption:

effects observed, non-treatment-related

Description (incidence and severity):

Of the fetuses that died, about 20% were classified as spat resorptions: their proportion increased somewhat with increasing doses of phenacetin, but without achieving statistically significant differences.

Dead fetuses:

not specified

Description (incidence and severity):

Of the fetuses that died, about 20% were classified as spat resorptions: their proportion increased somewhat with increasing doses of phenacetin, but without achieving statistically significant differences.

Changes in pregnancy duration:

not specified

Changes in number of pregnant:

not specified

Results (fetuses)

Fetal body weight changes:

effects observed, treatment-related

Reduction in number of live offspring:

not examined

Changes in sex ratio:

not examined

Changes in litter size and weights:

not examined

Anogenital distance of all rodent fetuses:

not examined

Changes in postnatal survival:

not examined

External malformations:

not specified

Skeletal malformations:

effects observed, treatment-related

Description (incidence and severity):

The foetuses unespecifically damage in the sense of a concomitant retardation of skeletal development.

Visceral malformations:

not examined

Effect levels (fetuses)

Key result

Dose descriptor:

LOEL

Effect level:

150 mg/kg bw/day

Based on:

test mat.

Basis for effect level:

other: Retarded skeletal development and increase in supernumerary ribs

Any other information on results incl. tables

Results on placental passage of phenacetin: 

On the 21st day of pregnancy, 2h after administration of 1200 mg/kg, an average of 89 µg/ml was found in the blood of the dams and 51 µg/g phenacetin in the tissue of the homogenized foestuses.

After a dose of 150 mg/kg, the corresponding values were 15 µg/ml and 12 µg/g. The small difference between maternal and fetal concentrations is apparently due to the fact that the phenacetin was determined in the blood of the mother and in the toal homogenate of the foestus.

 

Table 1. Blood concentrations after oral administration of 1200 mg/kg test item (mean values of 6 animals each with standard deviation of the individual values): 

Withdrawl Std.	Phenacetin µg/ml	p-Phenetidine µg/ml	HEmiglobina (% of total Hb)
0	<0.25	-	<1
1	85.0 ± 30.5	7.8 ± 2.5	14.7 ± 6.7
2	87.0 ± 19.2	8.7 ± 2.8	25.1 ± 7.8
3	53.7 ± 16.0	11.0 ± 3.8	27.8 ± 11.3
12	29.1 ± 18.0	13.5 ± 6.4	9.0 ± 5.2
24	17.8 ± 8.7	0.9 ± 0.6	1.8 ± 0.8

Table 2. Frequency of pregnancies and false pregnancies 

	Covered animals	Gravide	Not gravid
Control animals (n=40)	36	31	5
150 mg/kg phenacetin (n=20)	19	16	3
300 mg/kg (n=20)	18	17	1
600 mg/kg (n=20)	19	14	5
1200 mg/kg (n=20)	20	10	10

Table 3. Weight gain of dams during the entire pregnancy, average weight of foetuses per litter and placental weights 

	Mother animals (g)	Fetuses (g)	Placents (g)
Control animals (n=35)	46.8 ± 13.3	3.03 ± 0.27	0.59 ± 0.07
150 mg/kg Phenacetin (n=15)	42.2 ± 14.1	2.93 ± 0.18	0.56 ± 0.05
300 mg/kg (n=17)	43.5 ± 11.0	2.90 ± 0.34	0.59 ± 0.07
600 mg/kg (n=14)	41.4 ± 11.8	2.59 ± 0.36	0.61 ± 0.06
1200 mg/kg (n=8)	20.0 ± 18.0	2.15 ± 0.34	0.63 ± 0.15

 

Applicant's summary and conclusion

Conclusions:

In a developmental toxicity study, while there was no evidence of teratogenicity, delayed skeletal growth and an increase in supernumerary ribs was observed at doses of 150 mg/kg bw and above in the same study.

Executive summary:

Developmental toxicity study was performed on test item by oral administration of phenacetin at doses of 150, 300, 600 and 1200 mg/kg bw/d from gestational days 0 to 20. Control group was fed without test item and the vehicle was wheat starch. Oral administration is reportedly associated with reduced fetal weight, although the magnitude of the effect is not stated. While there was no evidence of teratogenicity, delayed skeletal growth and an increase in supernumerary ribs was observed at doses of 150 mg/kg bw and above in the same study.