Ibuprofen

Carcinogenicity

Description of key information

No carcinogenic properties detected in rat or mice.

Key value for chemical safety assessment

Carcinogenicity: via oral route

Link to relevant study records

Reference

Reference 1

Endpoint:

carcinogenicity: oral

Type of information:

experimental study

Adequacy of study:

key study

Study period:

December 1971(begin of dosing) to January 1974 (sacrifice of the last animals)

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

comparable to guideline study

Principles of method if other than guideline:

Chronic toxicity and carcinogenicity study. The test substance was administered in the diet to groups of Wister rats (40 males and 40 females per group) at dose levels of 20, 60 and 120 mg/kg bw daily for 2 years.

GLP compliance:

no

Remarks:

pre-GLP study

Specific details on test material used for the study:

- Name of test material (as cited in study report): Ibuprofen
- Analytical purity: 99.3%, loss on drying 0.03%
- Impurities (identity and concentrations): Lead (<3 ppm), nickel (2 ppm), sulfated ash (negligible), related compounds (0.7%)
- Purity test date: 1970-04-23
- Lot/batch No.: CT 76615
- Expiration date of the lot/batch: no data
- Test substance was synthesized by the oxime route.

Species:

rat

Strain:

Wistar

Details on species / strain selection:

Ash-Wistar specific-pathogen-free rats

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Scientific Products Farm
- Age at study initiation: newly weaned;
- Fasting period before study: no
- Housing: 4 per cage, plastic cages with wire floors
- Diet (ad libitum): Oxoid breeding diet
- Water: ad libitum,
- Acclimation period: 2 weeks

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22 ± 3°C

IN-LIFE DATES: From: November 1971 - To: January 1974 (sacrifice)

Route of administration:

oral: feed

Vehicle:

unchanged (no vehicle)

Details on exposure:

DIET PREPARATION
- Rate of preparation of diet (frequency): weekly
- Mixing appropriate amounts with (Type of food): Oxoid breeding diet
- Storage temperature of food: no data

The test substance was incorporated into standard laboratory diet (Oxoid Breeding Diet) using a Robart Mixer, freshly each week. The rats were provided with the diet containing the test substance throughout the experiment for a maximum period of 109 weeks; the concentration of the compound in the diet was adjusted as necessary in order to maintain a constant dose intake.

After acclimatisation, the rats remained untreated for 3 weeks to allow pretreatment observations.

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

no details given

Duration of treatment / exposure:

2 years, maximum: 109 weeks

Frequency of treatment:

continuously in the diet

Post exposure period:

none

Dose / conc.:

20 mg/kg bw/day (nominal)

Remarks:

20.3 mg/kg bw/day actual ingested (males)
20.0 mg/kg bw/day actual ingested (females

Dose / conc.:

60 mg/kg bw/day (nominal)

Remarks:

60.2 mg/kg bw/day actual ingested (females
61.7 mg/kg bw/day actual ingested (females)

Dose / conc.:

120 mg/kg bw/day (nominal)

Remarks:

122.3 mg/kg bw/day actual ingested (males)
122.2 mg/kg bw/day actual ingested (females)

No. of animals per sex per dose:

40 males and 40 females per group
An additional 8 male and 8 female rats in the control group and 4 males and 4 females in the dosed groups were kept to replace animals that died or were killed in the first 3 months.

Control animals:

yes, plain diet

Details on study design:

- Post-exposure recovery period in satellite groups: none
- Section schedule rationale: random:
After two weeks of acclimatisation to the laboratory conditions, the rate were allocated to groups by distribution of litter mates to have as far as possible at least one of each sex in each group and to give a similar bodyweight range within each group. They were left untreated for a further three weeks to permit predosing observations.

Positive control:

no

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: Yes

DETAILED CLINICAL OBSERVATIONS: Yes

BODY WEIGHT: Yes
- Time schedule for examinations: twice weekly

FOOD CONSUMPTION AND COMPOUND INTAKE:
Food consumption was estimated each week from two weeks before treatment began; this was done for each cage by recording the amount of food provided weekly and the amount recovered at the end of the week uneaten and as spillage.

HAEMATOLOGY and CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: at 26, 52, 78 and 104 weeks of treatment
- How many animals: 8 per sex of both control and high dose group
- Parameters examined: erythrocyte count, reticulocyte count, hemoglobin, hematocrit, leukocyte count (total and differential), thrombocyte count, Thrombotest reducing substances, urea nitrogen

URINALYSIS: Yes
- Time schedule for collection of urine: 26, 52, 78 and 103 weeks; overnight sample (16-hour collection)
- Metabolism cages used for collection of urine: Yes
- Parameters examined: urine volume, sodium and potassium, chloride (at 103 weeks only). glutamic-oxaloacetic transaminase (GOT), pH, specific gravity, glucose, reducing substances, protein, blood, bilirubin, urobilinogen, ketones, urine sediment.

KIDNEY FUNCTION TEST:
Kidney function tests were performed on males and females from each of the high-dose and control groups at 26, 52, 78 and 103 weeks, and on males and females in the mid dose group at 52 weeks.

Sacrifice and pathology:

GROSS PATHOLOGY: Yes
HISTOPATHOLOGY: Yes
Organs and tissues examined:
adrenal, aorta, brain, cervix, vagina, epididymis, eyes, heart (atrium and ventricle), kidneys, lacrimal gland, larynx, liver, lung, lymph nodes (cervical and thoracic) mammary gland, muscles, ovaries, pancreas, prostate with seminal vesicles, salivary glands (parotid and submaxillary), sciatic nerve, skin, spleen, testes, thyroid, trachea and oesophagus, ureters, uterus, femur, spinal column, pituitary, bone marrow, gastrointestinal tract, mesenteric lymph nodes, bladder, samples of growths and abnormal tissues.

All surviving rats were killed by carbon dioxide inhalation after 104 to 109 weeks treatment and examined. Where possible rats that died or were killed during treatment were examined similarly except that plasma biochemical analyses were not performed.
Plasma biochemical analyses were performed on samples separated from blood obtained by heart puncture immediately after death: parameters examined: glutamic-pyruvate transaminase (GPT), glutamic-oxaloacetic transaminase (GOT), bilirubin, alkaline phosphatase (AP), sodium and potassium.

Other examinations:

KIDNEY FUNCTION TEST:
Kidney function tests were performed on males and females from each of the high-dose and control groups at 26, 52, 78 and 103 weeks, and on males and females in the mid dose group at 52 weeks.

Statistics:

The 't'- test was used for statistical analysis of the body weight, haematological, blood biochemical and urinalysis data. In the case of the body weight data, values from treated and control rats were compared using an estimate of variance derived from the analysis of variance between all groups. For all other data the corresponding comparison was made using an estimate of variance derived from the analysis of variance between the control and particular dosed groups examined.

Clinical signs:

no effects observed

Description (incidence and severity):

No clinical sign related to treatment was observed; the incidence of general signs of ill-health such as red tears, skin abscesses and cornified skin on the feet was similar in each of the control and treated groups.

Mortality:

mortality observed, non-treatment-related

Description (incidence):

At the end of the treatment period, 16/40 male and 10/40 female aninals had died in the control group. 22/40 males and 17/40 females in the 20 mg/kg bw/day group. 16/40 males and 14/40 females in the 60 mg/kg bw/day group.
Mortality was higher among males than females in all groups, though for each sex the number of survivors to the end of the test was similar for the control and treated groups. In the low-dose group mortality was slightly greater than in the control group for the last 20 weeks, but this was considered to be incidental to treatment as there was no comparable difference at the two higher doses.

Body weight and weight changes:

no effects observed

Description (incidence and severity):

Throughout the experiment the growth rates of the males and females in the treated groups were similar to the growth rates of the respective control animals.

Food consumption and compound intake (if feeding study):

no effects observed

Description (incidence and severity):

Food consumption was similar in each of the control and treated groups throughout the experiment, with the females consistently eating more than the males relative to their body weight. The average daily doses ingested over the 2-year period by males were 20.3, 60.2 and 122.3 mg/kg bw and by females 20.0, 61.7 and 122.2 mg/kg bw.

Haematological findings:

no effects observed

Description (incidence and severity):

The mean haematological values of rate in the high-dose and control groups were similar at all times. At 26 weeks the reticulocyte count in the females and thrombotest activity in the males given the high dose were statistically significantly different from the control values, as was the reticulocyte count in the males given the high dose at 52 weeks, but all the deviant values were within the normal range for the age of the animals at these times.

Clinical biochemistry findings:

effects observed, treatment-related

Description (incidence and severity):

The mean blood concentrations of reducing substances and urea-N were generally similar at all times in the rats given the high dose and the controls. However, there was a statistically significant difference between the urea-N concentrations in the males given the high dose and the controls at 26 and 78 weeks, being greater than and less than the control values at these times respectively, though all the deviant values were within the normal range. The apparently greater mean urea-N concentration at 104 weeks in the females given the high dose compared to the control value was due to a single rat and this animal also had a high concentration of reducing substances. At 104 weeks two control males also had high urea-N concentrations.
Terminal Plasma Biochemistry:
The level of GPT activity showed a dose-related increase that was greater in males than females. In comparison with control values there was a statistically significant difference in the values of the males in each of the treated groups and of the females in the intermediate-dose group. The value for the females in the high-dose group did not attain a level of statistical significance.
The level of GOT activity was greater to a statistically significant degree in males given the high dose than in control males. Males in the two lower-dose groups and females in all treated groups had GOT levels that were not significantly different from control values.
In the males there was a dose-related increase in alkaline phosphatase activity that attained a level of statistical significance only in the two higher-dose groups, whereas in the females there was no significant difference between values in the control and treated groups.
Bilirubin, sodium and potassium concentrations were unaffected by treatment at any dose level.

Urinalysis findings:

effects observed, treatment-related

Description (incidence and severity):

The results from the urine analyses performed at regular intervals during the experiment showed no consistent dose-related effect, though changes in various parameters were sometimes noted in the treated rats and more often in the high-dose group.

Organ weight findings including organ / body weight ratios:

not specified

Gross pathological findings:

effects observed, treatment-related

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Description (incidence and severity):

The only specific pathological effects observed in treated animals when compared with the controls were an increased incidence of renal papillary lesions, namely necrobiosis in the rats of both sexes given 60 und 120 mg/kg daily and papillary necrosis in one rat given 60 mg/kg daily and in five given 120 mg/kg daily, and a variable degree of gastrointestinal damage that was more in evidence in the high-dose group.
Chronic respiratory disease and small foci of parenchymal necrosis in the liver were seen as part of the normal pathological changes that occur in the strain of rats used; however, pulmonary und liver lesions were more prevalent in treated than control males, und particularly in those given 120 mg/kg daily. According to the authors, this was considered a secondary effect due to the stress of treatment and injury to the kidneys and gastrointestinal tract leading to a lowered resistance to spontaneous infection.

Histopathological findings: neoplastic:

no effects observed

Description (incidence and severity):

The distribution, type and time of appearance of tumors in the treated and control animals were similar and there was no significant difference in the incidence of animals bearing tumours whether malignant or of all types.

Other effects:

effects observed, treatment-related

Description (incidence and severity):

Kidney function tests occasionally revealed an increase in urine flow rate, decrease in urine specific gravity und some loss of concentrating ability in the rats given 120 mg/kg daily compared with the control animals; haematuria was detected in a single male in the high-dose group from one year of treatment onwards.

Key result

Dose descriptor:

NOAEL

Remarks:

Carcinogenicity

Effect level:

> 120 mg/kg bw/day (nominal)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: No neoplastic lesions were observed at any dose level.

Dose descriptor:

NOAEL

Remarks:

Toxicity

Effect level:

20 mg/kg bw/day (nominal)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: No adverse effects observed at this dose-level

Dose descriptor:

LOAEL

Remarks:

Toxicity

Effect level:

60 mg/kg bw/day (nominal)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

histopathology: non-neoplastic

Reference 2

Endpoint:

carcinogenicity: oral

Type of information:

experimental study

Adequacy of study:

key study

Study period:

October 1976 to 1970

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Principles of method if other than guideline:

The purpose of this study was to present a detailed account of an 80-wk carcinogenicity study in mice with the test substance which was initiated as part of the safety evaluation programme on the compound.

GLP compliance:

no

Remarks:

pre-GLP study

Specific details on test material used for the study:

- Name of test material (as cited in study report): Ibuprofen

Species:

mouse

Strain:

other: Schofield

Sex:

male/female

Details on test animals or test system and environmental conditions:

- Source: commercial supplier, no further data
- Housing: 10 per cage
- Diet: Oxoid Breeding Diet, measured amount,
- Water: Tap water, ad libitum
- Acclimation period: several weeks.

Route of administration:

oral: feed

Vehicle:

unchanged (no vehicle)

Details on exposure:

DIET PREPARATION
- Rate of preparation of diet (frequency): weekly
- Mixing appropriate amounts with (Type of food): Oxoid Breeding Diet
The medicated diet was prepared freshly each week. The concentration of the test substance incorporated into the diet was adjusted, at first weekly and then less often, so that the nominal dose ingested was 300 mg/kg daily for the first 43 wk. Because of morbidity in the ibuprofen-treated group, from wk 44 and for the remainder of the experiment the dietary concentration was adjusted to provide a nominal dose of 100 mg/kg daily.

Analytical verification of doses or concentrations:

not specified

Duration of treatment / exposure:

80 weeks

Frequency of treatment:

continuously in the diet

Post exposure period:

none

Dose / conc.:

300 mg/kg bw/day (nominal)

Remarks:

weeks 1 - 43

Dose / conc.:

100 mg/kg bw/day (nominal)

Remarks:

weeks 44 - 80

No. of animals per sex per dose:

50

Control animals:

yes, plain diet

Details on study design:

no further data

Positive control:

no

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: daily

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: daily

BODY WEIGHT: Yes
- Time schedule for examinations: three times per week (first three months), once weekly (remainder of the study period

FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study):
Food consumption in each cage was estimated weekly and the average daily intake calculated, no further data.

WATER CONSUMPTION: No

OPHTHALMOSCOPIC EXAMINATION: No

HAEMATOLOGY: No

CLINICAL CHEMISTRY: No

URINALYSIS: No

NEUROBEHAVIOURAL EXAMINATION: No

Sacrifice and pathology:

GROSS PATHOLOGY: Yes
macroscopic examination of major organs and tissues,

HISTOPATHOLOGY: Yes
organs/tissues examined: adrenals, brain, eyes, heart, kidneys, liver, lungs, mesenteric lymph node, ovaries, pancreas, salivary gland; spleen, testes, thyroid, urinary bladder, uterus, gastrointestinal tract, samples of neoplasms/lesions suspected to be neoplastic

All animals (decedents and survivors) were intended to be subjected to post-mortem examination. However, a total of 27 animals (5 males and 6 females in the control group and 10 males and 6 females in the dosed group), were found dead and too badly autolysed, and sometimes cannibalised, for possible histological study. To these must be added a rogue male in the control groups killed in wk 6 and a dosed male that was sick and killed in wk 3 on which no histological study was conducted.

Statistics:

no data

Clinical signs:

effects observed, treatment-related

Description (incidence and severity):

Some mice developed skin lesions with scab formation and hair loss, and became unsightly in appearance. This condition, which was equally prevalent among either sex in the two groups, was probably due to an ectoparasitic infestation. Those animals that were most severely affected and showed a serious loss of condition were killed prematurely.

Mortality:

mortality observed, treatment-related

Description (incidence):

At the end of the treatment period, 6/50 treated males, 24/50 treated females, 14/50 control males and 12/50 control females had survived. In the treated group, 19 males and 9 females died or had to be killed until study week 43. Therefore, the dose was reduced to 100 mg/kg bw/d for the remainder of the study. Most of the decedents had gastrointestinal damage, principally intestinal ulceration that was observed on gross or microscopic examination or both.

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

There was no significant difference in weight gain between the dosed and control groups for the first 15 wk of the experiment. Afterwards the dosed group gained less weight. From wk 16 weight gain of the dosed males was depressed for 10 wk and was then similar to that of the control males until wk 35 when the average bodyweight reached a plateau, whereas the control males continued to increase in weight until wk 50 and then their average bodyweight slowly declined. From wk 16 weight gain of the dosed females was depressed for 20 wk, and from wk 35 onwards their average bodyweight showed similar fluctuations to that of the control females.

Gross pathological findings:

effects observed, treatment-related

Description (incidence and severity):

The only specific pathological effect was gastrointestinal damage, the males appearing more susceptible than the females before adjustment in dose level.

Histopathological findings: non-neoplastic:

no effects observed

Description (incidence and severity):

Both in the dosed and control groups, mice that survived and those that died or were killed earlier showed the usual histological abnormalities characteristic of advancing age in the particular strain of mouse employed. The majority of the animals showed signs of chronic respiratory disease and many had varying degrees of glomerulonephritis and, in the liver, fatty change, congestion vacuolation, lymphoid infiltration and sometimes focal necrosis. Abnormalities commonly observed in other organs included:
Heart: myocarditis, focal fibrosis;
Lymph nodes: reactive hyperplasia;
Salivary gland: intercalary hyperplasia;
Spleen: congestion, lymphocytic hyperplasia;
Testis: tubular degeneration;
Ovaries: cystic;
Uterus: cystic, endometritis.

Histopathological findings: neoplastic:

no effects observed

Description (incidence and severity):

The dosed group contained fewer tumor-bearing animals than the control group, 21 males and 26 females compared with 36 males and 34 females. There were also fewer animals with malignant tumors in the dosed than in the control group, 11 males and 18 females compared with 14 males and 27 females. These numbers include animals with lesions suspected of being neoplastic. The earliest tumor observed was a reticulum cell neoplasm in wk 29 in a control male, whilst in the dosed group the earliest tumor occurred in a male with lymphatic leukemia in wk 35. The commonest tumor were of the lympho-reticular system, lung, liver and uterus; the time for their appearance and incidence was not significantly different in the dosed and control groups. There was, however, an apparent difference in the incidence of adenocarcinoma of the mammary gland, only one dosed female bearing this type of tumor compared with nine control females. Tumors occurring in other organs or tissues ware recorded in only one or two animals in the dosed or control groups and have no toxicological significance.

Key result

Dose descriptor:

NOAEL

Remarks:

Carcinogenicity

Effect level:

300 mg/kg bw/day (nominal)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

histopathology: neoplastic

Dose descriptor:

NOAEL

Remarks:

Toxicity

Sex:

male/female

Basis for effect level:

other: Gastrointestinal damage was observed.

Remarks on result:

not determinable because of methodological limitations

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Carcinogenicity: via inhalation route

Endpoint conclusion

Endpoint conclusion:

no study available

Carcinogenicity: via dermal route

Endpoint conclusion

Endpoint conclusion:

no study available

Justification for classification or non-classification

Classification for carcinogenicity toxicity is considered not warranted in accordance with EU Classification, Labeling and Packaging of Substances and Mixtures (CLP) Regulation No. 1272/2008.

Additional information

In a chronic toxicity and carcinogenicity study (BASF 1972), the test substance was administered in the diet to groups of Wister rats (40 males and 40 females per group) at dose levels of 0, 20, 60 and 120 mg/kg bw daily for 2 years. An additional 8 male and 8 female rats in the control group and 4 males and 4 females in the dosed groups were kept to replace animals that died or were killed in the first 3 months. Mortality, general condition, growth rate and food consumption were unaffected by treatment. At the end of the treatment period, 16/40 male and 10/40 female aninals had died in the control group. 22/40 males and 17/40 females in the 20 mg/kg bw/day group. 16/40 males and 14/40 females in the 60 mg/kg bw/day group and, 16/40 males and 9/120 females in the 20 mg/kg bw/day group. Mortality was higher among males than females in all groups, though for each sex the number of survivors to the end of the test was similar for the control and treated groups. In the low-dose group mortality was slightly greater than in the control group for the last 20 weeks, but this was considered to be incidental to treatment as there was no comparable difference at the two higher doses. No dose-related effect on haematological values or blood concentrations of urea-nitrogen und reducing substances, measured at six-monthly intervals throughout the study, were observed. Kidney function tests occasionally revealed an increase in urine flow rate, decrease in urine specific gravity und some loss of concentrating ability in the rats given 120 mg/kg daily compared with the control animals; haematuria was detected in a single male in the high-dose group from one year of treatment onwards. Plasma biochemical values, measured at the end of dosing, showed a dose-related increase in glutamic-pyruvate transaminase in both sexes and alkaline phosphatase in the males; glutamic-oxaloacetic transaminase was elevated only in the males given 120 mg/kg daily. The only specific pathological effects observed in treated animals when compared with the controls were an increased incidence of renal papillary lesions, namely necrobiosis in the rate of both sexes given 60 and 120 mg/kg daily und papillary necrosis in one rat given 60 mg/kg daily and in five given 120 mg/kg daily, and a variable degree of gastrointestinal damage that was more in evidence in the high-dose group. Chronic respiratory disease and small foci of parenchymal necrosis in the liver were seen as part of the normal pathological changes that occur in the strain of rats used; however, pulmonary and liver lesions were more prevalent in treated than control males, und particularly in those given 120 mg/kg daily. This is considered a secondary effect due to the stress of treatment and injury to the kidneys and gastrointestinal tract leading to a lowered resistance to spontaneous infection. The distribution, type and time of appearance of tumors in the treated and control animals were similar and there was no significant difference in the incidence of animals bearing tumors whether malignant or of all types. Hence it is concluded that ibuprofen was not carcinogenic in the Ash-Wistar rat.

In another carcinogenicity study (BASF 1976), the test substance was administered in the diet fed to mice for 80 wks, at a dose level of 300 mg/kg daily for the first 43 wk and at 100 mg/kg daily for the remainder of the experiment. At the end of the treatment period, 6/50 treated males, 24/50 treated females, 14/50 control males and 12/50 control females had survived. In the treated group, 19 males and 9 females died or had to be killed until study week 43. Therefore, the dose was reduced to 100 mg/kg bw/d for the remainder of the study. Most of the decedents had gastrointestinal damage, principally intestinal ulceration that was observed on gross or microscopic examination or both. Some mice developed skin lesions with scab formation and hair loss, and became unsightly in appearance. This condition, which was equally prevalent among either sex in the two groups, was probably due to an ectoparasitic infestation. Those animals that were most severely affected and showed a serious loss of condition were killed prematurely. Growth was depressed but food consumption was not adversely affected. The only specific pathological effect observed was gastrointestinal damage, the males appearing more susceptible than the females before adjustment in dose level. There was no evidence that treatment generally influenced the type, incidence, or time of appearance of the neoplastic changes that occurred, hence it is concluded that ibuprofen is not carcinogenic in the mouse. Fewer mice given the test substance developed mammary tumors than control mice.