Lexikon

acute oral toxicity refers to those adverse effects occurring following oral administration of a single dose of a substance, or multiple doses given within 24 hours.

acute systemic toxicity testing is the estimation of the human hazard potential of a substance by determining its systemic toxicity in a test system (currently animals) following an acute exposure. Its assessment has traditionally been based on the median lethal dose (LD50) value - an estimate of the dose of a test substance that kills 50% of the test animals. For a substance to have systemic toxic effects it must be absorbed by the body and distributed by the circulation to sites in the body where it exerts toxic effects. The liver may transform a circulating drug or chemical to another form (biotransformation), and this new metabolite may be the one causing the observed toxicity.

Acute systemic toxicity is assessed following oral, dermal, and/or inhalation exposure(s) - depending upon the anticipated routes of human exposure to the substance. The Globally Harmonized System (GHS), which is scheduled for implementation in 2008, defines acute toxicity as "those adverse effects occurring following oral or dermal administration of a single dose of a substance, or multiple doses given within 24 hours, or an inhalation exposure of 4 hours"

Sources:
UNECE, 2004, p. 109.
http://www.alttox.org/ttrc/toxicity-tests/acute/

short term toxicity. The adverse effects of chemical substances which result either from a single exposure or from multiple exposures in a short space of time.
In animal testings "acute" is the toxicity, when the adverse effects occurs within 14 days of the administration of the substance. In ecotoxicity testings acute toxicity is defined as a period of time shorter, than the generation time of the testorganism. The endpoints used for the quantitative characterisation of acute toxicity are: EC₅₀, LC₅₀ or ED₅₀ and LD₅₀ values.

Acute toxicity is distinguished from chronic toxicity, which describes the adverse health effects from repeated exposures, often at lower levels, to a substance over a longer time period months or years.

acute toxicity concerns the adverse effects, which may result from a single exposure or multiple exposures within 24 hours to a substance in toxicity tests. Exposure relates to the oral, dermal or inhalation routes. Assessment of the acute toxic potential of a chemical is necessary to determine the adverse health effects that might occur following accidental or deliberate short-term exposure: the types of toxic effects, their time of onset, duration and severity, the dose-response relationships, and the sex differences in response. The investigated damages can be clinical signs of toxicity, abnormal body weight changes, and/or pathological changes in organs and tissues, which in some cases may result in death.

Source: REACH