Breed · Dog

Chihuahua: adverse event reports

FDA breed label "Chihuahua" · single-breed animals only

Read this first · FDA's caveat, in its words

An API dataset query result cannot be used to estimate the risk associated with the product or compare one drug or device product with another. When looking at the results, be aware that there is no certainty that the reported drug or device caused the adverse event. This dataset should not be the sole source of information for clinical decision-making or other assumptions about the safety or effectiveness of a product. The adverse event may have been related to an underlying disease, other drugs used at the same time or other non-drug related sources. FDA Center for Veterinary Medicine

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Not veterinary advice. This site lists what was reported to FDA. For an animal that is unwell, contact a veterinarian.

25,766reports, 1987–20262.6% of dog reports

1,007reports, 12 months to March 20261,119 in the 12 months before

35.9%classed serious, as reportedall dogs: 38.3%

15.6%name milbemycin oxime + spinosadall dogs: 13.1%

25,766 adverse event reports received by FDA describe an animal recorded as Chihuahua (FDA breed label "Chihuahua"). That is 2.6% of all reports about dogs. Crossbred animals are not counted here, only reports that give this single breed.

1,007 reports arrived in the 12 months to March 2026, down 10% from 1,119 in the 12 months before. A breed's count mostly mirrors how common the breed is; registration and ownership figures by breed are not public data, so no per-animal rate can be given.

By active ingredient, the drugs named most often are milbemycin oxime + spinosad, spinosad and ivermectin + pyrantel pamoate. Milbemycin Oxime + Spinosad is named in 15.6% of this breed's reports, about the same share as in reports about all dogs (13.1%).

The terms listed most often are vomiting (22%), lack of efficacy (ectoparasite) - flea (11.5%) and lethargy (11.4%). Vomiting appears in 22% of reports, about the same share as in all dog reports (19.7%). 35.9% of reports stating seriousness were classed as serious, against 38.3% for dogs overall.

Drugs named most often, by active ingredient

Active ingredients recorded for the drug	Reports	Share of Chihuahua reports	Share of all dog reports
Milbemycin Oxime + Spinosad	4,012	15.6%	13.1%
Spinosad	3,150	12.2%	5.8%
Ivermectin + Pyrantel Pamoate	2,184	8.5%	14.9%
Fluralaner	2,048	7.9%	6.7%
Moxidectin	1,377	5.3%	5%
Afoxolaner	1,269	4.9%	5.7%
Selamectin	874	3.4%	3%
Nitenpyram	825	3.2%	1.1%
Pyrantel Pamoate + Sarolaner	772	3%	5.1%
Imidacloprid + Moxidectin	613	2.4%	1.3%
Lufenuron + Milbemycin Oxime	555	2.2%	2.7%
Carprofen	531	2.1%	4.8%
Oclacitinib	526	2%	2.9%
Sarolaner	516	2%	1.7%
Melarsomine Dihydrochloride	507	2%	2.3%
Pimobendan	505	2%	0.6%
Milbemycin Oxime	490	1.9%	3%
Meloxicam	486	1.9%	0.8%
Milbemycin Oxime + Praziquantel	425	1.6%	3.1%
Maropitant	377	1.5%	1.2%

Ordered by report count. Differences from the species column often come from body size (which drugs a breed is prescribed) and from how common the breed was in the years a drug sold most. FDA states that these data cannot be used to estimate risk or to compare one product with another. Brand and manufacturer names are masked by FDA in these records.

Signs listed in reports

share of Chihuahua reports listing the termall dog reports

Vomiting22%5,665
Lack of efficacy (ectoparasite) - flea[the product did not have the expected effect: fleas]11.5%2,974
Lethargy[unusually tired or inactive]11.4%2,929
Emesis[vomiting]8.3%2,131
Diarrhoea[diarrhea]7.3%1,871
Anorexia[not eating]5.7%1,466
Seizure NOS[seizure, type not specified]4.6%1,177
Depression[dull, quiet or withdrawn]4.5%1,169
Lack of efficacy - NOS[the product did not have the expected effect]4.3%1,106
Ataxia[unsteady, uncoordinated movement]3.7%946
Death3.3%851
Pruritus[itching]3.1%799
Shaking2.9%746
Behavioural disorder NOS[behaviour change, type not specified]2.8%710
Ineffective, heartworm larvae[legacy FDA term: the product did not have the expected effect (heartworm larvae)]2.5%646
Overdose[more than the labelled amount was given]2.3%594
Elevated alanine aminotransferase (ALT)[a liver enzyme above the normal range]2.3%593
Accidental exposure[exposure that was not intended]2.3%587
Not eating2.2%577
Emesis (multiple)[vomiting more than once]2.2%572
Trembling2.1%542
Lack of efficacy (endoparasite) - heartworm[the product did not have the expected effect: heartworm]2.1%540
Lack of efficacy (endoparasite) - hookworm[the product did not have the expected effect: hookworms]1.8%467
Lack of efficacy (flea)[the product did not have the expected effect: fleas]1.8%464
Vocalisation[crying out or unusual noise]1.8%460

Age and weight

Age of the animal

Under 1 year10.7%2,757

1 to 3 years27.5%7,080

4 to 7 years25.7%6,610

8 to 11 years19.2%4,952

12 years and over12%3,082

Age not given5%1,285

Weight of the animal

Under 5 kg (11 lb)71.7%18,484

5 to 9.9 kg (11–22 lb)23.2%5,970

10 to 24.9 kg (22–55 lb)1.2%316

25 to 44.9 kg (55–99 lb)0%5

45 kg and over (99 lb+)0%7

Weight not given3.8%984

Coloured bar: Chihuahua reports. Grey bar: all dog reports.

Trend and outcomes

Reports by month FDA received them. The newest months are incomplete because FDA posts reports with a delay of three to six months.

Outcome recorded in the report

Recovered/Normal29.2%7,512

Recovered with Sequela3%770

Ongoing18.6%4,797

Died3.9%1,017

Euthanized1.3%327

Outcome Unknown25.3%6,525

Beside all dogs

Measure	Chihuahua	All dogs
Reports	25,766	985,675
Latest 12 months	1,007	53,292
Classed serious, of reports stating it	35.9%	38.3%
Death or euthanasia recorded, per 1,000 reports	52.2	55

Questions about Chihuahua reports

How many FDA adverse event reports involve Chihuahuas?

25,766 reports through March 2026, 2.6% of reports about dogs; 1,007 in the latest 12 months.

Which drugs are named most often in Chihuahua reports?

By active ingredient: milbemycin oxime + spinosad (4,012), spinosad (3,150), ivermectin + pyrantel pamoate (2,184), fluralaner (2,048) and moxidectin (1,377). Brands are masked in the public data.

What signs are reported most for this breed?

vomiting (22%), lack of efficacy (ectoparasite) - flea (11.5%), lethargy (11.4%), emesis (8.3%) and diarrhoea (7.3%).

Is the Chihuahua more sensitive to certain drugs?

Report counts cannot answer that. They show what was reported, not what a drug did, and they are not adjusted for how many Chihuahua animals exist or were treated. Breed-related drug sensitivities that are established are described on FDA-approved labels; a veterinarian is the person to ask about an individual animal.

Why are crossbreds not included?

FDA records crossbred animals with one or more component breeds. Counting them under each component would double count, so breed pages use single-breed reports only. Crossbreds remain in the species totals.

How do I report a problem?

Call the drug company using the number on the label, or send Form FDA 1932a to FDA. See the guide on how to report.

Where this comes from. Counts are built from the openFDA Animal & Veterinary adverse event bulk files released 28 Sep 2026, which hold reports FDA's Center for Veterinary Medicine received through 31 Mar 2026. openFDA masks brand and manufacturer names in these files, so drugs are counted by the active ingredients each record discloses and no figure is attributed to a brand, application or company. Ingredient names, and the separate reference lists of approved products, follow the FDA Green Book as of 30 Sep 2026. Breed names are FDA's labels rearranged into everyday order ("Chihuahua" becomes "Chihuahua"). No report text, lot numbers or reporter details are published. See the methodology and sources; FDA's record is authoritative, and corrections are handled within five working days.