Paracetamol

Carcinogenicity

Description of key information

based on the summareis paracetamol didi not induce any significant neoplastic effects  and is found to be non carcinogenic.

Key value for chemical safety assessment

Carcinogenicity: via oral route

Link to relevant study records

Reference

Endpoint:

carcinogenicity: oral

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other:

Qualifier:

according to guideline

Guideline:

other: FDA Good Laboratory Practice Regulations (21 CFR Part 58).

Principles of method if other than guideline:

The carcinogenic potential of acetaminophen in experimental animal mouse has been examined in a 2 year study.

GLP compliance:

yes

Specific details on test material used for the study:

SOURCE OF TEST MATERIAL
- Source and lot/batch No.of test material: Acetaminophen was obtained from S.B. Penick & Company.
Lot number 7042-LAR-5 was used in most of the 2-year study and lot number 7032-LFR-57 was used in the final 2 to 6 months of the 2-year studies.
- Purity: greater than 99%

RADIOLABELLING INFORMATION (Not applicable)
- Radiochemical purity: N/A
- Specific activity:N/A
- Locations of the label:N/A
- Expiration date of radiochemical substance:N/A

STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material:The bulk chemical was stored in sealed containers protected from light at 25 degC.
- Stability under test conditions: Stability studies performed with HPLC found that acetaminophen was stable as a bulk chemical when stored protected from light for 2 weeks at temperatures up to 60 degC.Throughout the studies, the bulk chemical was stored in sealed containers protected from light at 25 degC. Stability of the bulk chemical was monitored by the study laboratory using infrared and ultraviolet spectroscopies. No change in the study material was detected.

Species:

mouse

Strain:

B6C3F1

Sex:

male/female

Details on test animals or test system and environmental conditions:

- Source: Charles River Breeding Laboratories (mice: Portage, MI)
- Age at study initiation: 8-9 weeks old
- Quarentine :15 to 20 days
- Housing:five per cage
- Diet : NIH-07 Rat and Mouse Ration, powdered (Zeigler Bros., Inc., Gardners, PA); available ad libitum
- Water: Tap water (City of Worcester Public Water Supply) via outside-the-cage automatic watering system (Edstrom Industries, aterford, WI); available ad libitum
- Method of Animal Distribution: Animals distributed to weight classes, assigned to cages and dose groups using random number tables, and randomized to initial rack position.
- Method of Animal Identification: Ear punch
- Cages: Polycarbonate,See-Through II System (Lab Products, Inc., Rochelle Park, NJ)
- Bedding : AspenBed heat-treated hardwood chips (American ExcelsiorCo., Baltimore, MD); changed
twice weekly
- Cage Filters: Nonwoven fiber filters (Snow Filtration, Cincinnati, OH)

Temperature: 18°-25° C
Relative Humidity: 5%-71%
Fluorescent light: 12 hours/day
Room air changes: 11.2-11.6/hour

IN-LIFE DATES: From: 28 July 1982 (males) or 9 August 1982 (females) to 18 July 1984 (males) or 30 July 1984 (females)

Route of administration:

oral: feed

Vehicle:

other: Diet

Details on exposure:

DIET PREPARATION
- Rate of preparation of diet (frequency):Weekly
- Mixing appropriate amounts with (Type of food):The dose formulations were prepared by mixing appropriate quantities of acetaminophen with feed in a blender. Dose formulations were prepared weekly during the 2 year study.
- Storage temperature of food: 25 degC.

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Studies were conducted by the analytical chemistry laboratory to determine homogeneity and stability of the dosed feed preparations. For homogeneity analyses, the formulations were extracted with methanol and the concentrations determined by an ultraviolet method at 247 nm. For the stability studies,the
formulations were extracted using a methanol/acetic acid (95/5) solution and then injected into a HPLC system equipped with a μBondapak C18 column and a 254 nm detector. The mobile phase was methanol:water (24:76) with a flow rate of 1mL/minute.Periodic analyses of the dose formulations of acetaminophen were conducted at the study laboratory and at the analytical chemistry laboratory using ultraviolet spectroscopy.During the 2-year studies, the dose formulations were analyzed at least once every 8 weeks using a slightly modified ultraviolet spectroscopic procedure.

Duration of treatment / exposure:

103 weeks

Frequency of treatment:

Daily (7 days/week)

Dose / conc.:

0 ppm

Remarks:

0 mg/kg bw/day

Dose / conc.:

600 ppm

Remarks:

100 mg/kg bw/day

Dose / conc.:

3 000 ppm

Remarks:

500 mg/kg bw/day

Dose / conc.:

6 000 ppm

Remarks:

1000 mg/kg bw/day

No. of animals per sex per dose:

0 (0 mg/Kg bw/day): 60 males and 60 females
600 ppm (100 mg/Kg bw/day): 60 males and 60 females
3000 ppm (500 mg/Kg bw/day): 60 males and 60 females
6000 ppm (1000 mg/Kg bw/day): 60 males and 60 females

At 15 months, 10 mice per sex per dose group were randomly selected for interim evaluations.

Control animals:

yes, concurrent vehicle

Details on study design:

At 15 months, 10 mice per group were randomly selected for interim evaluations.

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: No data
- Time schedule:
- Cage side observations checked in table [No.?] were included.

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule:Clinical findings noted during the daily checks were recorded.

BODY WEIGHT: Yes
- Time schedule for examinations:Mice were weighed at study initiation, once a week for either 15 weeks (males) or 12 weeks (females) and monthly thereafter.

FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study):Feed consumption was measured 1 week per month through week 12 and every 4 weeks thereafter.
- Food consumption for each animal determined and mean daily diet consumption calculated as g food/kg body weight/day: Yes
- Compound intake calculated as time-weighted averages from the consumption and body weight gain data: Yes / No / Not specified

FOOD EFFICIENCY:No
- Body weight gain in kg/food consumption in kg per unit time X 100 calculated as time-weighted averages from the consumption and body weight gain data: No

WATER CONSUMPTION AND COMPOUND INTAKE (if drinking water study): No
- Time schedule for examinations:

OPHTHALMOSCOPIC EXAMINATION: No
- Time schedule for examinations:
- Dose groups that were examined:

HAEMATOLOGY: Yes
Blood was drawn from the tail of mice and the following hematology parameters measured: hematocrit, hemoglobin concentration, erythrocyte count, total leukocyte count, leukocyte differential aunt, mean cell volume, mean cell hemo- globin, mean cell hemoglobin concentration, and methemoglobin.

CLINICAL CHEMISTRY:Yes
- Serum albumin and glucose concentrations in micewere determined on blood drawn from the jugular vein of mice.

URINALYSIS: Yes
- Time schedule for collection of urine:One week prior to the interim evaluation urine was collected over a 24-hour period and the urine volume and total protein concentration (mice only) were determined.

NEUROBEHAVIOURAL EXAMINATION: No
- Time schedule for examinations:
- Dose groups that were examined:
- Battery of functions tested: sensory activity / grip strength / motor activity / other:

Sacrifice and pathology:

GROSS PATHOLOGY: Yes
Method of Sacrifice:Carbon dioxide asphyxiation
Necropsies were performed on all animals found moribund, designated for the 15-month interim evaluations, or surviving to the end of the 2-year studies. At necropsy, all organs and tissues were examined for gross lesions, and all major tissues were fixed and preserved in 10% neutral buffered formalin, processed and trimmed, embedded in paraffin, sectioned, and stained with hematoxylin and eosin for microscopic examination.

HISTOPATHOLOGY: Yes
Complete histopathology on all animals that died, were killed moribund or were killed at month 15 or study termination. Complete histopathology on all animals thal died, were killed moribund or were killed at month IS or study termination.Tissue examined included: adrenal gland, blood smear,bone(sternebrae including marrow), brain,epididymis, esophagus,gallbladder (mice),heart, kidney, large intestine (cecum, CD-Ion, rectum), liver,lung, lymph nodes (mandibular,mesenteric),mammarygland, nose, ovary,
pancreas, parathyroid gland, pituitary gland,prostate gland, salivary gland, seminal vesicles, skin, small intestine (duodenum, ileum,jejunum), spleen, stomach, tesles, thymus, thyroid gland,trachea, urinary bladder, uterus, and gross lesions and tissue masss (with regional lymph nodes).Clinical pathology studies conducted at month 15. Hematology: hematocrit, hemoglobin, erythrocyte count, leukocyte count and differential,mean cell volume, mean cell hemoglobin, meancell hemoglobin concentration.Clinical chemistry (mice only): albumin,glucosc,methemoglobin.Urinaly-six totalprotein(mice only). urine volume.

Other examinations:

Analysis of Neophm Incidence :
A quality assessment pathologist reviewed selected tissues for accuracy and consistency of lesion diagnosis. The following tissues were reviewed in all animals in all dose groups: male and female mice, thyroid gland. All diagnosed neoplasms in all tissues other than those already mentioned were reviewed in all animals, and all diagnoses (neoplasms and nonneoplastic lesions) were reviewed from a randomly selected 10% of the control and highdose animals of each sex in each species. In addition, selected tissues from all animals in all dose groups of male mice were examined for the presence of proliferative lesions (hyperplasia and neoplasia). The tissues examined included:male mice, adrenal gland, kidney, and nose. The kidneys from all male mice were also reviewed for the presence of renal tubule regeneration.

Statistics:

Survival Analyses
The probability of survival was estimated by the product-limit procedure of Kaplan and Meier (1958) and is presented in the form of graphs. Animals were censored from the survival analyses at the time they were found dead from other than naturalcauses. Animals dying from natural causes were not censored. S
tatistical analysis for a possible dose-related effect on survival used the method of Cox (1972)for testing two groups for equality and Tarone’s (1975)life table test to identify dose-related trends. All reported P values for the survival analysis are two sided.

Calculation of Incidence
The incidence of neoplasms or nonneoplastic lesions is givenas the ratio of the number of animals bearing such lesions at a specific anatomic site to the number of animals in which the site was examined.In most instances, the denominatorsinclude only those animals for which the site was examined histopa
thologically. However, when macroscopic examination was required to detect lesions (e.& oral cavity) prior to tissue sampling for histopathology, or when lesions (e.&, lymphoma) could have occurred at multiple sites, the denominators consist of the number of animals on which a necropsy was performed.

Analysis of Neoplasam Incidence
The primary statistical method used was a logistic regression, which assumed that the diagnosed neoplasms were discovered as the result of death from an unrelated cause and thus did not affect the risk of death. In this approach, neoplasm prevalence was modeled as a logistic function of chemical exposure and time. Both linear and quadratic terms in time were incorporated initially, and the quadratic term was eliminated if it did not significantly enhance the fit of the model. The dosed and vehicle control groups were compared on the basis of the likelihood score test for the regression coefficient of dose.

Clinical signs:

no effects observed

Dermal irritation (if dermal study):

not specified

Mortality:

mortality observed, treatment-related

Description (incidence):

Survival of male and female mice receiving acetaminophen was similar to that of the controls.

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

Mean body weights of exposed mice were generally lower than those of the controls throughout the studies.

Food consumption and compound intake (if feeding study):

effects observed, treatment-related

Description (incidence and severity):

The average daily feed consumption of male and female mice in all dose groups was similar to that of the controls . The average amount of acetaminophen consumed per mouse per day was approximately 90,450, or 1,OOO mgkg for low-, mid-, or high-dose males and 110,600, or 1,200 mgkg for low-,mid-, or high-dose females.

Food efficiency:

not examined

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

not examined

Ophthalmological findings:

not examined

Haematological findings:

effects observed, treatment-related

Clinical biochemistry findings:

no effects observed

Description (incidence and severity):

No chemical-related clinical findings were observed.

Urinalysis findings:

not specified

Behaviour (functional findings):

not specified

Immunological findings:

not specified

Organ weight findings including organ / body weight ratios:

not specified

Gross pathological findings:

effects observed, treatment-related

Neuropathological findings:

not specified

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Description (incidence and severity):

The incidence of thyroid follicular cell hyperplasia increased with dose among groups of exposed male and female mice, there was no increase in the incidence of follicular cell neoplasms.

A renal tubule hyperplasia occurred in one low-dose and two high-dose males and a renal tubule adenoma was present in one low-dose and one high-dose male.

Histopathological findings: neoplastic:

effects observed, treatment-related

Description (incidence and severity):

No neoplasms or evidence of compound-related toxicity were observed in mice after 15 months of acetaminophen exposure. Changes in hematologic parameters did not show any obvious relation to chemical exposure and were considered incidental.

No neoplasms or hyperplasias of the renal tubules were observed in female mice.

Other effects:

no effects observed

Description (incidence and severity):

Sentinel Animals:
Positive serologic titers for mouse hepatitis virus were detected in 5 of 10 serum samples at 24 months, however, there was no clinical evidence of disease associated with infection. In other NTP studies, subclinical infection with this virus was shown to have no effect on body weight, survival, or neoplasm incidence.

Details on results:

Historical Control Data
Although the concurrent control group is the first and most appropriate control group used for valuation,there are certain instances in which historical control data can be helpful in the overall assessment of neoplasm incidence. Consequently, neoplasmincidences from the NTP historical control data base for 2-year studies (Haseman et aL, 1984, 1985) are included for neoplasms appearing to show compoundrelated effects.






OTHER FINDINGS No data available

Dose descriptor:

LOAEL

Effect level:

600 ppm

Based on:

test mat.

Sex:

male/female

Basis for effect level:

histopathology: neoplastic

histopathology: non-neoplastic

Remarks on result:

other: Effect type: carcinogenicity (migrated information)

Critical effects observed:

not specified

Conclusions:

Under the conditions of these 2-year feed studies, there was no evidence of carcinogenic activity of acetaminophen in male and female B6C3F1 mice that received 600, 3,000, or 6,000 ppm. Nonneoplastic lesions associated with exposure to acetaminophen included increased incidences of thyroid follicular cell hyperplasia in male and female mice.
Thus we can conclude that the LOAEL (lowest observed adverse effect level) of acetaminophen (paracetamol) to mice by the oral route was observed at a dose concentration of 600 ppm (calculated as : 100 mg/kg bw/day) in a 2 year study period.

Executive summary:

The 2 year study was conducted to evaluate toxic effects of continuous exposure to acetaminophen (paracetamol).Mice were fed diets containing 0, 600, 3,000, or 6,000 ppm acetaminophen were given continuously to groups of 60 mice of each sex for up to 103 weeks. After 65 weeks of exposure, 10 animals from each group were evaluated for histopathology and for hematology, urinalysis, and clinical chemistry parameters. Survival of exposed and control mice was similar throughout the study. Mean body weights of mice that received acetaminophenwere generally lower than those of the controls throughout the study. Although the incidence of thyroid follicular cell hyperplasia increased with dose among groups of exposed male and female mice, there was no increase in the incidence of follicular cell neoplasms. Renal tubule hyperplasia occurred in one low-dose and two high-dose males and a renal tubule adenoma was present in one low-dose and one high-dose male.

Under the conditions of these 2-year feed studies, there was no evidence of carcinogenic activity of acetaminophen in male and female B6C3F1 mice that received 600, 3,000, or 6,000 ppm. Nonneoplastic lesions associated with exposure to acetaminophen included increased incidences of thyroid follicular cell hyperplasia in male and female mice.

Thus from above findings we can conclude that the LOAEL (lowest observed adverse effect level) of acetaminophen (paracetamol) to mice by the oral route was observed at a dose concentration of 600 ppm (calculated as : 100 mg/kg bw/day) in a 2 year study period.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

NOAEL

100 mg/kg bw/day

Study duration:

chronic

Species:

rat

Carcinogenicity: via inhalation route

Endpoint conclusion

Endpoint conclusion:

no study available

Justification for classification or non-classification

Based on the above summaries Paracetamol was the LOAEL was found to be ranging from 100mg/kg whereas the NOAEL ranges from 450to 650mg/kgbw/day exhibit no neoplastic effects at the dose concentration of 650mg/kgbw/day

Additional information

Carcinogenecity

U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES Public Health Service National Institutes of Health conducted a study to test the carcinogenic potential of acetaminophen in experimental animals in a 2 year study. B6C3F1 mice were use as a experimental animals with proper conditions and food and diet ad libitum. Animals were observed during the study period for all the parameters.Nonneoplastic lesions associated with exposure to acetaminophen included increased, incidences of thyroid follicular cell hyperplasia in male and female mice. Based on the results LOAEL was found to be 100mg/kg.

Another study reported by Kogo et.al (Jpn. J. Cancer Res. (Gann), 76, 79-85) reported , no neoplastic or nonneoplastic proliferative lesion in males were found in dosed groups at an in-creased incidence that could be clearly related to the treatment. Based on the results the NOAEL was predicted to be 450mg/kg bw. Therefore Under the test conditions of the present study, dietary administration of acetaminophen was not carcinogenic in F344/DuCrj rats.            Similar study of AAP in female rats, no neoplastic or nonneoplastic proliferative lesion were found in dosed groups at an increased incidence that could be clearly related to the treatment. Therefore the NOAEL was predicted as 650mg/kg bw.