Guidance for Industry
Single Dose Acute Toxicity Testing
for Pharmaceuticals
Center for Drug Evaluation and Research (CDER)
August 1996
        PT 1 GUIDANCE FOR INDUSTRY 1
SINGLE DOSE ACUTE TOXICITY TESTING FOR
PHARMACEUTICALS
I. INTRODUCTION
Acute toxicity studies in animals are usually necessary for any pharmaceutical intended for human
use. The information obtained from these studies is useful in choosing doses for repeat-dose
studies, providing preliminary identification of target organs of toxicity, and, occasionally,
revealing delayed toxicity. Acute toxicity studies may also aid in the selection of starting doses for
Phase 1 human studies, and provide information relevant to acute overdosing 
in humans.
II. DEFINITION
Acute toxicity is the toxicity produced by a pharmaceutical when it is administered in one or more
doses during a period not exceeding 24 hours.
III. TESTING PROCEDURES
The test compound should be administered to animals to identify doses causing no adverse effect
and doses causing major (life-threatening) toxicity. The use of vehicle control groups should be
considered. For compounds with low toxicity, the maximum feasible dose should be administered.
Acute toxicity studies in animals should ordinarily be conducted using two routes of drug
administration: (1) The route intended for human administration, and (2) intravenous
administration, if feasible. When intravenous dosing is proposed in humans, use of this route alone
in animal testing is sufficient.
1This guidance was originally published as a part of a proposed implementation document entitled U.S.
FDAs Proposed Implementation of International Conference on Harmonisation (ICH) Safety Working Group
Consensus Regarding new Drug Applications.  The Agency has revised this guidance based on comments it received
on the proposed implementation.  This approach, designed to facilitate the early stages of pharmaceutical development,
is not and ICH consensus position although it is considered to be in general agreement with the ICH position on acute
toxicity testing.  This guidance was published in the  Federal Register  on August 26, 1996 (61  FR 43934).  Although
this guidance does not create or confer any rights for or on any person and does not operate to bind FDA or the industry,
it does represent the Agencys current thinking on single dose acute toxicity testing for pharmaceuticals.  For additional
copies of this guideline, contact the Drug Information Branch, HFD-210, CDER, FDA, 5600 Fishers Lane, Rockville,
MD 20857 (Phone: 301-827-4573) or the Manufacturers Assistance and Communication Staff (HFM-42), CBER, FDA,
1401 Rockville Pike, Rockville, MD 20852-1448.  Send one self-addressed adhesive label to assist the offices in
processing your request.  An electronic version of this guidance is also available via Internet using the World Wide Web
(WWW) (connect to the CDER Home Page at http://www.fda.gov/cder and go to the Regulatory Guidance section).
1 Studies should be conducted in at least two mammalian species, including a nonrodent species
when reasonable. The objectives of acute studies can usually be achieved in rodents using small
groups of animals (for instance, three to five rodents per sex per dose). Where nonrodent species
are appropriate for investigation, use of fewer animals may be considered. Any data providing
information on acute effects in nonrodent species, including preliminary dose-range finding data
for repeat-dose toxicity studies, may be acceptable.
IV. OBSERVATION
Animals should be observed for 14 days after pharmaceutical administration. All mortalities,
clinical signs, time of onset, duration, and reversibility of toxicity should be recorded. Gross 
necropsies should be performed on all animals, including those sacrificed moribund, found dead,
or terminated at 14 days.
In addition, if acute toxicity studies in animals are to provide the primary safety data supporting
single dose safety/kinetic studies in humans (e.g., a study screening multiple analogs to aid in the
selection of a lead compound for clinical development), the toxicity studies should be designed to
assess dose-response relationships and pharmacokinetics. Clinical pathology and histopathology
should be monitored at an early time and at termination (i.e., ideally, for maximum effect and
recovery).
V. NOTE: ANIMAL PROTECTION
Studies should be designed so that the maximum amount of information is obtained from the
smallest number of animals. Calculating lethality parameters (e.g., LD<INF>50) using large
numbers of animals, as was done previously, is not recommended (see the  Federal Register of
October 11, 1988, 53 FR 39650).
To avoid causing excessive pain or tissue damage in the animals, pharmaceuticals with irritant or
corrosive characteristics should not be administered in concentrations that produce severe toxicity
solely from local effects.
2