National Toxicology Program

View guidelines and regulations relevant to acute systemic toxicity testing

Evaluation of an Up-and-Down Procedure for Acute Dermal Systemic Toxicity Testing

Poisoning by dermal exposure (absorption through the skin), while not as common as poisoning by ingestion, still accounted for nearly 180,000 poisonings in the United States in 2010. Regulatory agencies use information from acute dermal systemic toxicity tests using rabbits or rats to determine the potential of chemicals and chemical products to cause life-threatening health effects or death from acute dermal exposures. Test results are used as the basis for hazard classification and labeling and to inform consumers and workers how to avoid acute dermal exposures to hazardous chemicals and products during the handling, transport, and use of chemicals and products. NICEATM developed an up-and-down procedure for acute dermal systemic toxicity testing to reduce animal use for this purpose.

Validation Study of In Vitro Cytotoxicity Test Methods

In February 2008, ICCVAM forwarded recommendations on the use of two in vitro test methods to estimate starting doses for acute oral systemic toxicity tests. ICCVAM recommended that these test methods be considered before using animals for acute oral systemic toxicity testing, and that the methods should be used where determined appropriate. Data from the in vitro test methods should be used in a weight-of-evidence approach for determining starting doses for in vivo studies. Using these in vitro methods where appropriate is expected to reduce the number of animals required for each toxicity test.

Evaluation of In Vitro Cytotoxicity Test Methods

In vitro methods that use mammalian cell cultures and various cytotoxicity endpoints have been proposed as alternatives to in vivo acute oral systemic toxicity tests that use rodents. In vitro cytotoxicity test methods that measure basal cytotoxicity (general cytotoxicity that affects structures or processes intrinsic to all cell types) are not currently regarded as suitable replacements for rodent acute oral toxicity tests. However, some methods can be useful for establishing the starting dose for acute oral toxicity tests and thus reduce and refine animal use for such testing.

The use of in vitro cytotoxicity test methods to reduce animal use in acute oral systemic toxicity testing was evaluated at an October 2000 Workshop on In Vitro Methods for Assessing Acute Systemic Toxicity. A Guidance Document on Using In Vitro Data to Estimate In Vivo Starting Doses for Acute Toxicity was prepared by ICCVAM with the assistance of the workshop participants.

Development of OECD Test Guidelines for the Evaluation of Acute Systemic Toxicity

NICEATM and ICCVAM actively participate in the development of Test Guidelines and Guidance Documents relevant to toxicology and safety testing issued by the Organisation for Economic Co-operation and Development (OECD). OECD Test Guidelines are based on the most relevant internationally agreed-upon testing methods used by government, industry, and independent laboratories.

NICEATM and the ICCVAM Acute Toxicity Working Group have contributed to the development of a number of OECD Test Guidelines and Guidance Documents. Click on the heading above to view summaries of these activities.

Scientific Workshop on Acute Chemical Safety Testing: Advancing In Vitro Approaches and Humane Endpoints for Systemic Toxicity Evaluations

NICEATM, ICCVAM, and international partners sponsored a workshop to explore alternative methods for acute chemical safety testing. The goals of this February 2008 meeting of international experts in the fields of in vitro and in vivo toxicology and human and veterinary medicine were to:

1. Review the state-of-the-science and identify knowledge gaps (at the whole organism, organ system, cellular, and/or molecular levels) regarding the key in vivo pathways involved in acute systemic toxicity


2. Recommend how these knowledge gaps can be addressed by collecting mechanistic biomarker data during currently required in vivo safety testing


3. Recommend how in vivo key pathway information can be used to develop more predictive mechanism-based in vitro test systems and to identify biomarkers that may serve as earlier, more humane endpoints for in vivo test methods


4. Recommend how mechanism-based in vitro test systems and earlier, more humane endpoints can be used to further reduce, refine, and eventually replace animal use for acute systemic toxicity testing while ensuring the protection of human and animal health

The oral up-and-down procedure (UDP) is an alternative to the traditional oral median lethal dose (LD₅₀) test that reduces animal use. In the oral UDP, one animal is tested at a time, and the response of each animal to a test substance determines whether the next animal receives a higher or lower dose. A peer review panel sponsored by NICEATM and ICCVAM met in 2000 and 2001 to evaluate the revised oral UDP and develop recommendations. U.S. regulatory agencies adopted the ICCVAM recommendations on the revised oral UDP in 2003 and now accept oral UDPs methods issued by OECD and the U.S. Environmental Protection Agency, which have replaced the conventional acute oral systemic toxicity test method.