Methylprednisolone

Repeated dose toxicity: oral

Administrative data

Endpoint:

short-term repeated dose toxicity: oral

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Article referenced in TOXLINE

Data source

Reference

Reference Type:

publication

Title:

Unnamed

Year:

1959

Report date:

1958

Materials and methods

Test guideline

Qualifier:

no guideline followed

Principles of method if other than guideline:

Repeated-dose toxicity study was carried out with the test substance in dogs using daily oral doses of 0, 2.5 and 5 mg/kg bw/day for 42 days.

GLP compliance:

not specified

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

Methylprednisolone

EC Number:

201-476-4

EC Name:

Methylprednisolone

Cas Number:

83-43-2

Molecular formula:

C22H30O5

IUPAC Name:

11,17,21-trihydroxy-6-methylpregna-1,4-diene-3,20-dione

Test material form:

solid: particulate/powder

Test animals

Species:

dog

Strain:

other: mongrel

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Housing: The animals were confined in standard dog metabolism cages.
- Diet (e.g. ad libitum): During this time standard dog rations of both kibbled and canned food were fed.
- Water (e.g. ad libitum): Water was supplied ad libitum.

Administration / exposure

Route of administration:

oral: unspecified

Duration of treatment / exposure:

6 weeks

Frequency of treatment:

once a day, 7 days per week

Doses / concentrations

Doses / concentrations 1

Dose / conc.:

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

Doses / concentrations 2

Dose / conc.:

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

No. of animals per sex per dose:

Two animals per sex per dose

Examinations

Observations and examinations performed and frequency:

BODY WEIGHT:
All dogs were weighed weekly and dosages were adjusted accordingly. The logarithms of final and initial body weights of all surviving dogs were subjected to an analysis of covariance, and the logarithms of the final weights were adjusted to a fixed log initial weight.

HAEMATOLOGY:
At the beginning of the study, and prior to autopsy, standard bromo-sulfalein liver function tests, blood urea nitrogen determinations, blood glucose and creatinine determinations, as well as urinalyses were made. Complete hematologic examinations were also made at these times and each week during the experiment.

URINALYSIS:
Total urine excretion and urine specific gravity for each dog were measured daily. Aliquots of urine samples obtained on three consecutive days were pooled and stored under refrigeration. Sodium and potassium determinations were made on these pooled samples by means of a Perkin-Elmer flame photometer, using internal standards. An analysis of variance was performed on the urinary excretion data.

Sacrifice and pathology:

The study was terminated 6 weeks after its beginning with autopsy of all dogs remaining alive. Animals which died during the study were autopsied within 2 hours of death. At autopsy a complete examination was made and all gross changes were recorded in respect of each animal. The following organs were weighed: adrenals, thyroid, thymus, pancreas, heart, lungs, spleen, liver, gall bladder, stomach, small intestine, large intestine, kidneys, urinary bladder, gonads, prostate, brain, and pituitary. These organs, or portions of them, in addition to portions of mesenteric lymph node and rib, were fixed in neutral buffered formalin before paraffin embedding and staining of sections with routine hematoxylin and eosin.

Results and discussion

Results of examinations

Clinical signs:

no effects observed

Mortality:

no mortality observed

Body weight and weight changes:

effects observed, treatment-related

Haematological findings:

effects observed, treatment-related

Clinical biochemistry findings:

no effects observed

Urinalysis findings:

effects observed, treatment-related

Organ weight findings including organ / body weight ratios:

no effects observed

Gross pathological findings:

effects observed, treatment-related

Details on results:

CLINICAL SIGNS AND MORTALITY
No dogs died during the study.

BODY WEIGHT AND WEIGHT GAIN
The test substance at the rate of 5.0 mg/kg produced significant loss in body weight, but this effect was not observed in the group given the drug at the rate of 2.5 mg/kg.

HAEMATOLOGY
The hematologic examinations made at weekly intervals revealed no major departures from normal limits in the control dogs or in the dogs receiving the test substance. The principal change observed in these groups was a fall in packed cell volume, affecting some of the dogs only in each group. In only one animal, in the group receiving test substance at the rate of 5.0 mg/kg, did the packed cell volume fall below normal limits, to reach 28% at the end of the study.

CLINICAL PATHOLOGICAL
The results of all clinical pathological tests made at the outset of the study were within normal limits. The results of liver function tests, blood urea nitrogen, blood glucose determinations, and urinalyses made prior to autopsy were within normal limits for all dogs. Blood creatinine determinations at the end of the study showed somewhat lower values in all drug-treated animals as compared with those found in the control animals, but the differences were not significant, and no differences could be detected between the treated groups.

URINALYSIS
In all dogs the urine volume varied widely from day to day. The greatest single daily urine output in the control animals was less than 800 mL. The corresponding values for the drug-treated groups were 2.61. The figure is for animals given 5 mg/kg per day, but similar volumes were recorded in respect of the lower dose rate groups. The treated groups do not differ significantly from the controls in respect of mean daily urine volumes, although they do show some increase in mean daily urine excretion.
While the specific gravity of daily urine samples varied from day to day in all dogs. Although depression of specific gravity is seen in all treated groups, the differences between the controls and the test substance groups are not significant.
It does not appear possible to differentiate between the drug-treated groups in the regard of mean daily sodium and potassium excretion rates, but both sodium and potassium excretions in all treated groups are elevated over those of the control animals. However, only in regard to sodium excretion is the difference significant.

AUTOPSY
With the exception of changes in the liver and adrenals in all drug-treated dogs, no significant lesions were observed in any of the animals autopsied at the end of the study.
The livers of treated animals which survived for the full duration of the study were somewhat turgid and had rounded borders. They were tan to red-brown in color and somewhat mottled in appearance. They were moderately friable, and on section the lobular outlines appeared unusually distinct. Microscopic examination revealed some distortion of lobular architecture; large distended hepatic cells were arranged somewhat irregularly in the lobular centers. The cells were irregular in shape and had central nuclei. The cytoplasm consisted of a fine reticulum enclosing large vacuoles. The appearance was typical of glycogen overloading of the cells. Occasional livers presented small areas of focal necrosis, but these did not appear to be significant, except in two dogs which had received the test substance at the rate of 5 mg/kg. In these animals, centrilobular necrosis was quite pronounced. The extent of glycogen deposition in the livers of drug-treated animals appeared to vary generally with the dosage. No evidence of biliary stasis or other hepatic disruption was observed.
The adrenal glands appeared to be reduced in size on gross examination in all treated animals which survived the duration of the study. Microscopic examination revealed this reduction in size to be due to cortical atrophy confined principally to the zona fasciculata. The zona glomerulosa in all treated animals appeared prominent in contrast, but it was not possible to determine absolute increase in width.

ORGAN WEIGHTS
Adrenal, thymus, and liver weights calculated on a gram per kilogram body weight basis varied from those of the control animals in some of the drug-treated dogs, but these variations were not consistently related to dose or compound, and no group varied significantly from the controls in respect of any organ weight.

Effect levels

Basis for effect level:

other: No NOEL established

Remarks on result:

not measured/tested

Remarks:

Effect level not specified

Target system / organ toxicity

Critical effects observed:

not specified

Applicant's summary and conclusion

Conclusions:

The main effects in this study were reduced body weight, skeletal muscle atrophy, increased glycogen deposition in the liver and adrenal atrophy. No NOEL was established in this study.