Contains Non-Binding Recommendations 
 
141 
 
Guidance for Industry 
 
Studies to Evaluate the Safety of Residues of Veterinary 
Drugs in Human Food: Carcinogenicity Testing 
VICH GL28 
 
FINAL GUIDANCE 
 
 
(This version of the guidance replaces the version that was made available in May 24, 
2004. This guidance document has been revised to correct the contact information in 
regard to this document.) 
 
 
 
This final guidance is to ensure that the assessment of carcinogenic potential is appropriate 
to human exposure through residues of veterinary drugs in food. 
 
Comments and suggestions regarding the document should be submitted to Division of Dockets 
Management  (HFA-305),  Food  and  Drug  Administration,  5630  Fishers  Lane,  Rm.  1061, 
Rockville,  MD    20852.  Submit  electronic  comments  to  http://www.regulations.gov.    All 
comments should be identified with the Docket No. 2001D-0357.   
 
For questions regarding this document, contact the Division of Human Food Safety, Center for 
Veterinary  Medicine,  (HFV-150),  Food  and  Drug  Administration,  7500  Standish  Place, 
Rockville, MD 20855, 240-276-8211. 
 
 
U.S. Department of Health and Human Services 
Food and Drug Administration 
Center for Veterinary Medicine 
July 27, 2006 
  Page 1 Contains Non-Binding Recommendations 
 
VICH GL28 (SAFETY: CARCINOGENITICY) 
October 2002 
For implementation at Step 7 - Final 
 
 
 
 
 
S  
TUDIES TO EVALUATE 
 
THE SAFETY OF RESIDUES OF
V D H  
  ETERINARY  RUGS IN  UMAN
F : 
  OOD
C T  
ARCINOGENICITY  ESTING
 
 
 
 
Recommended for Implementation 
on October 2002 
by the VICH Steering Committee 
 
 
 
 
 
 
 
 
 
 
THIS GUIDANCE HAS BEEN DEVELOPED BY THE APPROPRIATE VICH EXPERT WORKING GROUP AND 
WAS SUBJECT TO CONSULTATION BY THE PARTIES, IN ACCORDANCE WITH THE VICH PROCESS. AT 
STEP 7 OF THE PROCESS THE FINAL DRAFT IS RECOMMENDED FOR ADOPTION TO THE REGULATORY 
BODIES OF THE EUROPEAN UNION, JAPAN AND USA. 
 
 
  Page 2 Contains Non-Binding Recommendations 
 
Studies to Evaluate the Safety of Residues of Veterinary Drugs in 
Human Food: Carcinogenicity Testing 
 
 
1.  INTRODUCTION............................................................................................................4 
1.1.  Objective of the guidance................................................................4 
1.2.  Background.....................................................................................4 
1.3.  Scope of the guidance.....................................................................4 
2.  CARCINOGENICITY ASSESSMENT............................................................................4 
2.1.  Overall approach.............................................................................4 
2.2.  Genotoxic compounds.....................................................................5 
2.3.  Non-genotoxic compounds..............................................................5 
2.4.   In vivo carcinogenicity testing..........................................................5 
2.4.1.  Existing relevant guidelines.......................................................................5 
2.4.2.  Species selection for long-term carcinogenicity testing.............................5 
2.4.3.  Number of animals and route of administration.........................................5 
2.4.4.  Dose selection for carcinogenicity testing..................................................6 
2.5.   In-life observations and pathological examination...........................6 
3.  REFERENCES...............................................................................................................6 
 
  Page 3 Contains Non-Binding Recommendations 
 
Studies to Evaluate the Safety of Residues of Veterinary Drugs in 
Human Food: Carcinogenicity Testing 
 
This  guidance  represents  the  Food  and  Drug  Administrations  (FDAs)  current  thinking  for 
establishing the safety of veterinary drug residues in human food.   It does not create or confer any 
rights for or on any person and does not operate to bind FDA or the public.  You can use an 
alternative approach if the approach satisfies the requirements of the applicable statute(s) and/or 
regulation(s).  If you want to discuss an alternative approach, contact the FDA staff responsible for 
implementing this guidance.  If you cannot identify the appropriate FDA staff, call the appropriate 
number listed on the title page of this guidance.  
1.  INTRODUCTION 
1.1.  Objective of the guidance 
In order to establish the safety of veterinary drug residues in human food, a number of 
toxicological evaluations are recommended including the assessment of potential to 
induce neoplasia. The objective of this guidance is to ensure that the assessment of 
carcinogenic potential is appropriate for human exposure to veterinary drug residues in 
human food. 
 
FDAs guidance documents, including this guidance, do not establish legally enforceable 
responsibilities.  Instead, guidances describe the Agencys current thinking on a topic and 
should be viewed only as recommendations, unless specific regulatory or statutory 
requirements are cited.  The use of the word should in Agency guidances means that 
something is suggested or recommended, but not required. 
1.2.  Background 
The assessment of carcinogenic potential has been identified as one of the key areas to 
be considered in the evaluation of the safety of veterinary drug residues in human food. 
Exposure to residues of veterinary drugs will usually occur at extremely low levels, but 
potentially for long periods, possibly over a lifetime. To ensure that substances that could 
pose carcinogenic potential at relevant exposure levels are adequately assessed, a 
number of issues should be considered, including genotoxicity, metabolic fate, species 
differences, and cellular changes.  
1.3.  Scope of the guidance 
This guidance sets out a recommended data-driven decision pathway to determine 
whether carcinogenicity studies should be conducted. It also provides guidance on the 
conduct of carcinogenicity studies. 
 
2.  CARCINOGENICITY ASSESSMENT 
2.1.  Overall approach 
The decision to undertake carcinogenicity testing should take into consideration, 1) the 
results of genotoxicity tests, 2) structure-activity relationships, and 3) findings in systemic 
toxicity tests that may be relevant to neoplasia in longer term studies. It should also take 
into consideration any known species specificity of the mechanism of toxicity. Any 
differences in metabolism between the test species, target animal species, and human 
beings should be taken into consideration. 
  Page 4 Contains Non-Binding Recommendations 
 
 
2.2.  Genotoxic compounds 
Many carcinogens have a genotoxic mode of action and it is prudent to regard 
genotoxicants as carcinogens unless there is convincing evidence that this is not the 
case. Clearly negative results for genotoxicity should usually be taken as sufficient 
evidence of a lack of carcinogenic potential via a genotoxic mechanism.  
2.3.  Non-genotoxic compounds 
Because it is generally believed that non-genotoxic compounds exhibit a threshold dose 
for carcinogenicity and human exposure to residues of veterinary drugs is low, non-
genotoxic compounds should not be routinely tested for carcinogenicity. Such tests may 
however be recommended if, for example, 1) the compound is a member of a chemical 
class known to be animal or human carcinogens, 2) available systemic toxicity studies 
with the compound identify potentially preneoplastic lesions or findings indicative of 
neoplasia, or 3) systemic toxicity studies indicate that the compound may be associated 
with effects known to be linked with epigenetic mechanisms of carcinogenicity that are 
relevant to humans.  
2.4.   In vivo carcinogenicity testing 
2.4.1.  Existing relevant guidelines 
The OECD Test Guideline 451 Carcinogenicity Studies Ref 1 contains study protocol 
guidelines and approaches for testing chemicals for carcinogenicity using experimental 
animals.    OECD Test Guideline serves as the basis for carcinogenicity testing of 
veterinary drugs with clarifications outlined in the following paragraphs.   
Note: Information derived from a combined assay for carcinogenicity and chronic toxicity 
(OECD Test Guideline 453 Combined Chronic Toxicity/Carcinogenicity StudiesRef 2 ) 
would also be acceptable. 
2.4.2.  Species selection for long-term carcinogenicity testing 
 
Carcinogenicity bioassays consisting of a two-year rat study and an 18-month mouse 
study are generally recommended. With appropriate scientific justification, carcinogenicity 
studies may be carried out in one rodent species, preferably the rat. A positive response 
in either test species should be considered indicative of carcinogenic potential. 
2.4.3.  Number of animals and route of administration 
 
Consistent with OECD Test Guideline 4511and common practice, a minimum of 50 rats 
and/or mice per dose (including concurrent controls) per sex is recommended for 
carcinogenicity testing. The route of administration for carcinogenicity testing of 
veterinary drug residues in human food should be oral, preferably dietary. Other routes of 
administration are not generally recommended for risk assessment of veterinary drug 
residues in human food.   
  Page 5 Contains Non-Binding Recommendations 
 
2.4.4.  Dose selection for carcinogenicity testing 
2.4.4.1. General 
It is recommended that at least three dose levels, in addition to a concurrent control 
group(s), be used for typical rodent carcinogenicity studies.  
 
2.4.4.2. Dose selection 
 
The high dose should be set to demonstrate a minimum toxic effect without affecting 
survivability due to effects other than carcinogenicity. Demonstration of a toxic effect in 
the carcinogenicity study, without compromising survivability or physiological 
homeostasis, ensures that the animals were sufficiently challenged and provides 
confidence in the reliability of a negative outcome.  
 
Factors recommended to be considered in establishing other doses include linearity of 
pharmacokinetics, saturation of metabolic pathways, anticipated human exposure levels, 
pharmacodynamics in the test species, the potential for threshold effects in the test 
species, available mechanistic information, and the unpredictability of the progression of 
toxicity observed in short-term rodent studies. It is recommended to set the lowest dose 
at a level that does not induce significant toxicity and is not lower than 10% of the highest 
dose. 
2.5.   In-life observations and pathological examination 
In-life observations and pathological examination, consistent with OECD Test Guideline 
451Ref 1, are recommended for carcinogenicity studies of veterinary drugs. Clinical 
pathology (hematology, urinalysis, and clinical chemistry) is not considered necessary or 
contributory to the assessment of neoplastic endpoints.  
 
3.  REFERENCES 
 
1. OECD. 1981. Test Guideline 451. Carcinogenicity Studies. In: OECD Guideline for the 
Testing of Chemicals. Organization for Economic Cooperation & Development, Paris. 
 
2.  OECD. 1981. Test Guideline 453. Combined ChronicToxicity/Carcinogenicity Studies.  
In: OECD Guideline for the Testing of Chemicals. Organization for Economic Cooperation 
& 
Development, Paris.   
 
 
 
  Page 6