The Importance of Pathology in Tox Studies
Understand what is happening in non-clinical species used,
and how it may or may not be interpreted in humans.
Investigation of Changes that may occur in Toxicology
Studies
• Clinical History of the species and strains used.
• Laboratory Investigation
- Clinical Chemistry
- Biochemistry – urine/faeces testing. Colour, crystals in
urine.
- Haematology
• Biopsy/Necropsy – at the end of the time (e.g. 90 days) –
undertake a schedule termination of the animal –start with
control animals – liver, kidney, heart and lungs checked. A
system is followed. Weighing is important – organ
enlargement, shrinkage (atrophy). Colour of organs. High-
dose is looked at too.
• Histological Examination – fix the tissue – 10% neutral
buffer, take organs leave for 7 days depending on thickness
and animal species – take them under normal histological
process.
After giving the drug, has the animal’s behaviour changed?
MTD – agitated, cuddled up, normal behaviour, test
temperature, secretions around the nose, mouth, eyes, fur
might feel damp, stains around the anus, darker urine, loose
stalls. – these factors are important as they indicate
something is wrong. When looking at the animal in the lab –
eating and drinking behaviours.
There are 4 themes of pathological changes to be considered.
, Introduction: Why the need for Pathology? – to look at
what the drug did to the organs, LT.
Disasters during this century, for example with thalidomide
(teratogenic effects) and the synthetic oestrogen
diethylstilboestrol in utero (carcinogenic) have taught us how
important it is to be watchful for the side-effects of drugs.
Contamination of food sources by pesticides and industrial
wastes also needs monitoring. Examples of compounds that
have been shown to be carcinogenic in experimental animals
(usually at relatively high doses) and that have entered the
human diet at low levels are certain pesticides (DDT and
dieldrin), as well as industrial contaminants (polychlorinated
biphenyls).
Also, the increased post-marketing withdrawal of medicinal
drugs and chemicals already on the market emphasize the
importance of safety assessment.
These examples underline the importance of conducting
safety research before products (drugs) come into the
market. Hence, the toxicological pathologist has an important
role to play with regard to risk evaluation as part of the
integral assessment of the safety of drugs on the basis of
animal testing.
Introduction: Why the need for Pathology?
The use of conventional toxicology studies with pathology is
usually sufficient to predict important adverse drug affects
and to support the safe use in clinical trials.
Understand what is happening in non-clinical species used,
and how it may or may not be interpreted in humans.
Investigation of Changes that may occur in Toxicology
Studies
• Clinical History of the species and strains used.
• Laboratory Investigation
- Clinical Chemistry
- Biochemistry – urine/faeces testing. Colour, crystals in
urine.
- Haematology
• Biopsy/Necropsy – at the end of the time (e.g. 90 days) –
undertake a schedule termination of the animal –start with
control animals – liver, kidney, heart and lungs checked. A
system is followed. Weighing is important – organ
enlargement, shrinkage (atrophy). Colour of organs. High-
dose is looked at too.
• Histological Examination – fix the tissue – 10% neutral
buffer, take organs leave for 7 days depending on thickness
and animal species – take them under normal histological
process.
After giving the drug, has the animal’s behaviour changed?
MTD – agitated, cuddled up, normal behaviour, test
temperature, secretions around the nose, mouth, eyes, fur
might feel damp, stains around the anus, darker urine, loose
stalls. – these factors are important as they indicate
something is wrong. When looking at the animal in the lab –
eating and drinking behaviours.
There are 4 themes of pathological changes to be considered.
, Introduction: Why the need for Pathology? – to look at
what the drug did to the organs, LT.
Disasters during this century, for example with thalidomide
(teratogenic effects) and the synthetic oestrogen
diethylstilboestrol in utero (carcinogenic) have taught us how
important it is to be watchful for the side-effects of drugs.
Contamination of food sources by pesticides and industrial
wastes also needs monitoring. Examples of compounds that
have been shown to be carcinogenic in experimental animals
(usually at relatively high doses) and that have entered the
human diet at low levels are certain pesticides (DDT and
dieldrin), as well as industrial contaminants (polychlorinated
biphenyls).
Also, the increased post-marketing withdrawal of medicinal
drugs and chemicals already on the market emphasize the
importance of safety assessment.
These examples underline the importance of conducting
safety research before products (drugs) come into the
market. Hence, the toxicological pathologist has an important
role to play with regard to risk evaluation as part of the
integral assessment of the safety of drugs on the basis of
animal testing.
Introduction: Why the need for Pathology?
The use of conventional toxicology studies with pathology is
usually sufficient to predict important adverse drug affects
and to support the safe use in clinical trials.
