Adverse effects of a drug that appear in a short period of time (usually less than 24 hours) after administration.

A range of pre-clinical studies are carried out to assess the risk of acute toxicity. Guidelines on the nature of these studies are provided by regulatory agencies. They are designed to ensure that risks are minimized when drugs are first tested on people.

Pre-clinical studies aim to generate data on factors such as toxic effects on the specific tissues affected, dependence on dose and the reversibility of any effects seen. Specific studies are required for drugs to be used in special groups, such as women of child-bearing age and children. Information from pre-clinical toxicology studies is used to determine starting dose and dose ranges for clinical trials, as well as to guide clinical monitoring.

Data on acute toxicity can be obtained from single-dose toxicity studies, maximum tolerated dose studies, dose-escalation studies or short-duration dose-ranging studies.