Months › 2021
Month received
November 2021: adverse event reports received
4,568 reports in the openFDA release of 28 Sep 2026
FDA's database holds 4,568 adverse event reports received in November 2021, against 4,799 in the same month a year earlier and a monthly average of 5,337 over the preceding 12 months.
74.2% of the month's reports concern dogs, 10.4% cats and 1.4% horses; the rest concern other species, exposed people, or give no species.
By active ingredient, the drugs named most often were pyrantel pamoate + sarolaner (606), ivermectin + pyrantel pamoate (586) and fluralaner (452), and the terms listed most often were vomiting (646), lack of efficacy (endoparasite) - heartworm (604) and lack of efficacy (endoparasite) - hookworm (337). Report volume has a seasonal shape, with more reports in the warmer months when parasite products are in heavier use.
The months around it
Drugs named most often, by active ingredient
| Active ingredients recorded for the drug | Reports | Share of the month's reports |
|---|---|---|
| Pyrantel Pamoate + Sarolaner | 606 | 13.3% |
| Ivermectin + Pyrantel Pamoate | 586 | 12.8% |
| Fluralaner | 452 | 9.9% |
| Moxidectin | 355 | 7.8% |
| Afoxolaner | 261 | 5.7% |
| Milbemycin Oxime + Praziquantel | 213 | 4.7% |
| Milbemycin Oxime + Spinosad | 176 | 3.9% |
| Nitenpyram | 121 | 2.6% |
| Sarolaner + Selamectin | 120 | 2.6% |
| Oclacitinib | 114 | 2.5% |
| Lotilaner | 101 | 2.2% |
| Sarolaner | 94 | 2.1% |
| Melarsomine Dihydrochloride | 88 | 1.9% |
| Selamectin | 83 | 1.8% |
| Trilostane | 69 | 1.5% |
Ordered by report count, which follows how widely each drug was in use. 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 most often
- Vomiting14.1%646
- Lack of efficacy (endoparasite) - heartworm[the product did not have the expected effect: heartworm]13.2%604
- Lack of efficacy (endoparasite) - hookworm[the product did not have the expected effect: hookworms]7.4%337
- Lethargy[unusually tired or inactive]7.2%328
- Lack of efficacy (ectoparasite) - flea[the product did not have the expected effect: fleas]6.2%284
- Lack of efficacy (ectoparasite) - tick NOS[the product did not have the expected effect: ticks]5.5%253
- Diarrhoea[diarrhea]4.8%220
- Death3.6%163
- Seizure NOS[seizure, type not specified]3.5%159
- Lack of efficacy (endoparasite) - roundworm NOS[the product did not have the expected effect: roundworms]3.2%148
- Lack of efficacy (bacteria) - Borrelia[the product did not have the expected effect: Borrelia (Lyme disease bacteria)]2.7%123
- Anorexia[not eating]2.3%103
- Lack of efficacy (bacteria) - NOS[the product did not have the expected effect: target not specified]2.3%103
- Not eating2.2%102
- Emesis (multiple)[vomiting more than once]2.1%96
Single ingredients, pooled
Species
Questions about November 2021
How many animal drug adverse event reports did FDA receive in November 2021?
4,568 reports are in the openFDA release of 28 Sep 2026. The same month a year earlier has 4,799.
Which drugs were named most often?
By active ingredient: pyrantel pamoate + sarolaner (606), ivermectin + pyrantel pamoate (586), fluralaner (452), moxidectin (355) and afoxolaner (261). Brands are masked in the public data.
Which signs were listed most often?
vomiting (646), lack of efficacy (endoparasite) - heartworm (604), lack of efficacy (endoparasite) - hookworm (337), lethargy (328) and lack of efficacy (ectoparasite) - flea (284).
Can the count for a month still change?
Yes. FDA posts reports quarterly with a delay of three to six months, so the newest months are incomplete and usually grow in later releases. Older months change little.
Does a busy month mean something went wrong that month?
Not by itself. The date is when FDA received the report, not when the event happened, and volume follows season, product launches and publicity. FDA states that "there is no certainty that the reported drug or device caused the adverse event" and that the event "may have been related to an underlying disease, other drugs used at the same time or other non-drug related sources."
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 1 Oct 2026. The month is the date FDA first received the report, not the date of the event. 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.