Drug profile

The FDA adverse-event record for Azathioprine

104 adverse-event reports submitted to the FDA Center for Veterinary Medicine reference Azathioprine. See the species affected, top reactions, and outcomes below.

104
adverse-event reports
31.7%
death-coded share
Dog
most-reported species
26
Lethargy (see also Central nervous system depression in 'Neurological') - top reaction
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Important: Adverse event reports do not establish that a drug caused or contributed to the event. Consult your veterinarian before making treatment decisions.
104
Total Reports
33
Deaths Reported
31.7%
Death Rate

Active Ingredients

Azathioprine

Administration Routes

OralUnknown

Species Affected

Dog 104

Most Affected Breeds

Retriever - Labrador 10
Shepherd Dog - German 7
Crossbred Canine/dog 6
Retriever - Golden 5
Shih Tzu 5
Spaniel - Cocker American 4
Shepherd Dog - Australian 4
Boxer (German Boxer) 3
Chihuahua 3
Terrier - Jack Russell 3

Most Reported Reactions

Lethargy (see also Central nervous system depression in 'Neurological') 26
Elevated serum alkaline phosphatase (SAP) 21
Anaemia NOS 20
Vomiting 19
Death by euthanasia 19
Immune mediated haemolytic anaemia 19
Other abnormal test result NOS 18
Diarrhoea 18
Leucocytosis NOS 17
Elevated alanine aminotransferase (ALT) 16
Thrombocytopenia 16
Anorexia 15

Outcome Breakdown

Ongoing
27 (27.8%)
Euthanized
19 (19.6%)
Recovered/Normal
17 (17.5%)
Outcome Unknown
16 (16.5%)
Died
14 (14.4%)
Recovered with Sequela
4 (4.1%)

Azathioprine Adverse Event Insights

104 reports name Azathioprine; 33 recorded a death outcome (31.7% of reported events, not a population-level mortality rate). Active ingredient: Azathioprine. Administration routes: Oral, Unknown.

By species: Dog (104 reports). By breed: Retriever - Labrador (10), Shepherd Dog - German (7), Crossbred Canine/dog (6).

Leading clinical signs: Lethargy (see also Central nervous system depression in 'Neurological') (26), Elevated serum alkaline phosphatase (SAP) (21), Anaemia NOS (20), Vomiting (19). Outcome, 97 coded reports: Ongoing leads at 27.8%.

Read these counts as reporting volume, not risk: per our methodology, a widely-prescribed drug will rack up more raw FDA reports in a given year than a rarely-used one at an identical true rate, so we recommend comparing within similar-exposure products rather than across the full 2025 catalog.

Source: FDA Center for Veterinary Medicine openFDA Animal & Veterinary Adverse Events (CVM AER) · 2025

Every figure on PlainBreed is rendered directly from FDA openFDA adverse event data, no number is typed in by an editor. This page draws directly on FDA openFDA data, no figure is typed in by an editor. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error.