AMES TEST (REVERSE MUTATION ASSAY IN SALMONELLA) ::
S.typhimurium tester strains such as TA98,TA100,TA102,TA1535,TA97 or Escherichia coli WP2 uvrA or Escherichia coli WP2 urvA (pKM101) are used In -vitro exposure (with and without metabolic activation S9 mix ) is done at a minimum of 5 log dose levels Solvent and positive control should be used Positive control may include 9-amino-acridine ,2-Nitro fluorine sodium azide and mitomycin C respectively in the tester strains mentioned above Each set should consist of at least three replicates A 2.5 fold (or more ) increase in number of revertants in comparison to spontaneous revertants would be considered positive
Carcinogenicity ::
Carcinogenicity studies are performed for all drugs that are expected to be clinically used for more than 6 months as well as for drugs used frequently in an intermittent manner in the treatment of chronic or recurrent conditions Carcinogenicity studies are also to be performed for drugs if there is concern about their carcinogenic potential emanating from previous demonstration of carcinogenic potential in the product class that is considered relevant to humans or where structure -activity relationship suggests carcinogenic risk or when there is evidence of preneoplastic lesions in repeated dose toxicity studies or when long -term tissue retention of parent compound or metabolite (s) results in local tissue reactions or other pathophysiological responses for pharmaceuticals developed to treat certain serious diseases Licensing Authority may allow carcinogenicity testing to be conducted after marketing permission has been granted
In instances where the life -expectancy in the indicated population is short (i.e.less than 2-3 years ) no long -term carcinogenicity studies may be required in cases where the therapeutic agent for cancer is generally successful and life is significantly prolonged there may be later concerns regarding secondary cancers When such drugs are intended for adjuvant therapy in tumour free patients or for prolonged use in non -cancer indications carcinogenicity studies may be /are needed
Carcinogenicity studies should be done in a rodent species (preferably rat ) Mouse may be employed only with proper scientific justification The selected strain of animals should not have a very high or very low incidence of spontaneous tumors
At least three dose levels are used The highest dose should be sub-lethal and it should not reduce the life span of animals by more than 10% of expected normal The lowest dose should be comparable to the intended human therapeutic dose or a multiple of it e.g. 2.5 x to make allowance for the sensitivity of the species The intermediate dose to be placed logarithmically between the other two doses An untreated control and (if indicated) a vehicle control group should be included The drug is administered 7 days a week for a fraction of the life span comparable to the fraction of human life spam over which the drug is likely to be used therapeutically Generally the period of dosing should be 24 months for rats and 18 months for mice
Observations should include macroscopic changes observed at autopsy and detailed histopathology of organs and tissues Additional tests for carcinogenicity (short-term bioassays neonatal mouse assay or tests employing transgenic animals ) may also be done depending on their applicability on a case to case basis
Each dose group and concurrent control group not intended to be sacrificed early should contain atleast 50 animals of each sex A high dose group for evaluation of pathology other than neoplasia contains 20 animals of each sex while the control group contains 10 animals of each sex Observation parameters include signs of intoxication effect on body weight food intake clinical chemistry parameters hematology parameters urine analysis organ weights gross pathology and detailed histopathology Comprehensive descriptions of benign and malignant tumour development time of their detection site dimensions histological typing etc should be given
0 Comments