Drug profile

The FDA adverse-event record for Diphenydramine

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

11
adverse-event reports
0.0%
death-coded share
Dog
most-reported species
4
Vomiting - 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.
11
Total Reports
0
Deaths Reported
0.0%
Death Rate

Active Ingredients

Diphenydramine

Administration Routes

OralUnknown

Species Affected

Dog 9
Cat 2

Most Affected Breeds

Terrier (unspecified) 2
Terrier - Bull - Staffordshire 2
Domestic Shorthair 2
Chihuahua 1
Maltese 1
Bichon Frise 1
Terrier - Bull - American Pit 1
Cattle Dog - Australian (blue heeler, red heeler, Queensland cattledog) 1

Most Reported Reactions

Vomiting 4
Pale mucous membrane 3
Hyposthenuria 3
Sleepiness - systemic disorder 3
Injection site pain 2
Panting 2
Lack of efficacy (ectoparasite) - flea 2
Polyuria 2
Polydipsia 2
Facial pruritus 2
Facial oedema 2
Vocalisation 2

Outcome Breakdown

Outcome Unknown
6 (54.5%)
Recovered/Normal
3 (27.3%)
Ongoing
2 (18.2%)

Diphenydramine Adverse Event Insights

11 reports name Diphenydramine; 0 recorded a death outcome (0.0% of reported events, not a population-level mortality rate). Active ingredient: Diphenydramine. Administration routes: Oral, Unknown.

By species: Dog (9 reports), Cat (2 reports). By breed: Terrier (unspecified) (2), Terrier - Bull - Staffordshire (2), Domestic Shorthair (2).

Leading clinical signs: Vomiting (4), Pale mucous membrane (3), Hyposthenuria (3), Sleepiness - systemic disorder (3). Outcome, 11 coded reports: Outcome Unknown leads at 54.5%.

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.