New supporting data to guide the use of evident toxicity in acute oral toxicity studies (OECD TG 420)

Currently there are three test guidelines (TG) for acute oral toxicity studies of substances or mixtures from the Organisation for Economic Co-operation and Development (OECD). TG 423 and TG 425 use lethality as an endpoint, while TG 420 replaces death with 'evident toxicity', defined as clear signs that exposure to a higher dose would result in death. However, the perceived subjectivity of 'evident toxicity' may be preventing wider use of TG 420. To address this, the UK National Centre for the Replacement, Refinement and Reduction of Animals in Research (NC3Rs) and the European Partnership for Alternative Approaches to Animal Testing (EPAA) collaborated to provide recommendations on the recognition of 'evident toxicity'. Historical data from acute oral toxicity studies were analysed for clinical signs at the lower dose that could have predicted death at the higher dose. Several signs including ataxia, laboured respiration, and eyes partially closed, alone or in combination, are highly predictive. Others such as lethargy, decreased respiration, and loose faeces have lower but still appreciable positive predictive value (PPV). The data has been used to develop recommendations to promote use of TG 420 and thus reduce the suffering and numbers of animals used in acute oral toxicity studies.

Acute oral toxicity evaluation of extracts of Hydrocotyle sibthorpioides in wister albino rats as per OECD 425 TG

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Toxicity was studied for Hydrocotyle sibthorpioides.

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LD₅₀ was found to be greater than 2000 mg/kg of body weight.

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Petroleum ether extract showed increase in somatomotor activity for short time.

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Methanolic and aqueous extract exhibited some change in Haematological parameters.

Hydrocotyle sibthorpioides (Family: Apiaceae) is a medicinal plant and is been a part of traditional cuisine. Hence, an acute toxicity study was performed to confirm its safety profile. Female rats (n=5) were randomly divided into 5 groups. One group served as the control and the other groups were been administered with the petroleum ether, chloroform, methanolic and aqueous extract of Hydrocotyle sibthorpioides at 2000 mg/kg body weight. Blood was collected at certain intervals to measure the haematological and biochemical parameters. The vital organs were isolated and preserved for histopathological examinations.

The result suggested that the LD₅₀ of all the extracts are greater than 2000 mg/kg body weight. There was no significant change in body weight, Behaviour, Renal Function test, Liver function test and Lipid profile. In haematological evaluation, there was an increase in RBC count and haemoglobin production post administration of methanolic and aqueous extract. The study suggested that the LD₅₀ of the plant is greater than 2000 mg/kg body weight of rats in all the extracts.