Breed · Dog
Mastiff: adverse event reports
FDA breed label "Mastiff" · single-breed animals only
3,093 adverse event reports received by FDA describe an animal recorded as Mastiff (FDA breed label "Mastiff"). That is 0.3% of all reports about dogs. Crossbred animals are not counted here, only reports that give this single breed.
0 reports arrived in the 12 months to March 2026, and none 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, ivermectin + pyrantel pamoate and spinosad. Milbemycin Oxime + Spinosad is named in 17.7% of this breed's reports, a larger share than in reports about all dogs (13.1%).
The terms listed most often are vomiting (21.1%), emesis (10.5%) and ineffective, heartworm larvae (7.6%). Vomiting appears in 21.1% of reports, about the same share as in all dog reports (19.7%). 40.5% 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 Mastiff reports | Share of all dog reports |
|---|---|---|---|
| Milbemycin Oxime + Spinosad | 547 | 17.7% | 13.1% |
| Ivermectin + Pyrantel Pamoate | 380 | 12.3% | 14.9% |
| Spinosad | 234 | 7.6% | 5.8% |
| Carprofen | 209 | 6.8% | 4.8% |
| Moxidectin | 204 | 6.6% | 5% |
| Fluralaner | 128 | 4.1% | 6.7% |
| Pyrantel Pamoate + Sarolaner | 121 | 3.9% | 5.1% |
| Afoxolaner | 114 | 3.7% | 5.7% |
| Milbemycin Oxime | 109 | 3.5% | 3% |
| Melarsomine Dihydrochloride | 105 | 3.4% | 2.3% |
| Oclacitinib | 98 | 3.2% | 2.9% |
| Deracoxib | 87 | 2.8% | 1.1% |
| Lufenuron + Milbemycin Oxime | 73 | 2.4% | 2.7% |
| Firocoxib | 68 | 2.2% | 0.8% |
| Selamectin | 61 | 2% | 3% |
| Sarolaner | 60 | 1.9% | 1.7% |
| Ivermectin | 52 | 1.7% | 1.3% |
| Milbemycin Oxime + Praziquantel | 43 | 1.4% | 3.1% |
| Meloxicam | 38 | 1.2% | 0.8% |
| Imidacloprid + Moxidectin | 35 | 1.1% | 1.3% |
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 Mastiff reports listing the termall dog reports
- Vomiting21.1%654
- Emesis[vomiting]10.5%326
- Ineffective, heartworm larvae[legacy FDA term: the product did not have the expected effect (heartworm larvae)]7.6%236
- Diarrhoea[diarrhea]7.3%227
- Lethargy[unusually tired or inactive]6.5%201
- Anorexia[not eating]5.9%183
- Death5.3%163
- Lack of efficacy (endoparasite) - heartworm[the product did not have the expected effect: heartworm]4.9%152
- Lack of efficacy (ectoparasite) - flea[the product did not have the expected effect: fleas]4.3%133
- Lack of efficacy - NOS[the product did not have the expected effect]4.3%132
- Depression[dull, quiet or withdrawn]4.2%131
- Lack of efficacy (endoparasite) - hookworm[the product did not have the expected effect: hookworms]3.7%113
- Death by euthanasia[the animal was euthanized]3.5%107
- Seizure NOS[seizure, type not specified]2.7%85
- Ataxia[unsteady, uncoordinated movement]2.6%80
- Underdose[less than the labelled amount was given]2.4%75
- Elevated creatinine[a kidney value above the normal range]2.3%72
- Ineffective, ascarids NOS[legacy FDA term: the product did not have the expected effect (ascarids nos)]2.2%69
- Weight loss2.2%69
- Elevated serum alkaline phosphatase (SAP)[a liver and bone enzyme above the normal range]2.2%67
- Other abnormal test result NOS[abnormal laboratory result, type not specified]2.1%66
- Leucocytosis NOS[high white blood cell count]2.1%65
- Elevated alanine aminotransferase (ALT)[a liver enzyme above the normal range]2.1%64
- Anaemia NOS[low red blood cell count]2%63
- Elevated blood urea nitrogen (BUN)[a kidney value above the normal range]2%63
Age and weight
Age of the animal
Weight of the animal
Coloured bar: Mastiff 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
Beside all dogs
| Measure | Mastiff | All dogs |
|---|---|---|
| Reports | 3,093 | 985,675 |
| Latest 12 months | 0 | 53,292 |
| Classed serious, of reports stating it | 40.5% | 38.3% |
| Death or euthanasia recorded, per 1,000 reports | 90.5 | 55 |
Questions about Mastiff reports
How many FDA adverse event reports involve Mastiffs?
3,093 reports through March 2026, 0.3% of reports about dogs; 0 in the latest 12 months.
Which drugs are named most often in Mastiff reports?
By active ingredient: milbemycin oxime + spinosad (547), ivermectin + pyrantel pamoate (380), spinosad (234), carprofen (209) and moxidectin (204). Brands are masked in the public data.
What signs are reported most for this breed?
vomiting (21.1%), emesis (10.5%), ineffective, heartworm larvae (7.6%), diarrhoea (7.3%) and lethargy (6.5%).
Is the Mastiff 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 Mastiff 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 ("Mastiff" becomes "Mastiff"). 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.