Pet Drug Reports

Lack of efficacy (endoparasite) - roundworm NOSin adverse event reports for animal drugs

Clinical sign, a VeDDRA term

In plain words: the product did not have the expected effect: roundworms.

Read this first. FDA says this about the data:

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 publishes these words. Source: Adverse Event Reports for Animal Drugs and Devices, read on . The data have the reports that FDA received through .

This page is not veterinary advice. For an animal that is ill, speak to a veterinarian.

Contacting a veterinarianHow to report to FDA

From March 1999 to June 2026, FDA received 14,372 adverse event reports for animal drugs that list this sign. That is 1% of the 1,378,761 reports that FDA received from January 1987 to June 2026. In the 12 months to June 2026, FDA received 1,864 reports that list this sign.

Of the 14,372 reports, 95% are about dogs. A report can list more than one sign and more than one drug. A report is not proof that a drug caused a sign.

By number of reports in all years, this sign is number 39 of 1,149 clinical signs with a page. Reports that list this sign fell by 11.6% in the 12 months to June 2026, compared with the 12 months before. Reports for all animal drugs fell by 4.6% in the same periods. The newest months can get more reports in a later update. Reports about dogs are 95% of the reports that list this sign, and 72.6% of all reports.

Drug pages with reports that list this sign

The table has every drug page with 20 or more reports that list this sign, in order of name. No count decides which drug is in the table. The table has 33 drug pages.

Show the 33 drug pages
Drug pages with 20 or more reports that list this sign, in order of name
Active ingredientsReports that list the sign
Afoxolaner189
Afoxolaner + Moxidectin + Pyrantel Pamoate644
Doramectin40
Emodepside + Praziquantel55
Eprinomectin + Esafoxolaner + Praziquantel176
Eprinomectin + Praziquantel32
Febantel + Praziquantel + Pyrantel Pamoate156
Fenbendazole86
Fluralaner72
Fluralaner + Moxidectin37
Gabapentin21
Imidacloprid21
Imidacloprid + Moxidectin156
Ivermectin48
Ivermectin + Praziquantel + Pyrantel Pamoate38
Ivermectin + Pyrantel Pamoate5,073
Lotilaner127
Lotilaner + Moxidectin + Praziquantel + Pyrantel Pamoate107
Lufenuron + Milbemycin Oxime417
Lufenuron + Milbemycin Oxime + Praziquantel458
Metronidazole37
Milbemycin Oxime110
Milbemycin Oxime + Praziquantel1,190
Milbemycin Oxime + Spinosad85
Moxidectin1,888
Oclacitinib37
Praziquantel + Pyrantel Pamoate39
Pyrantel Pamoate154
Pyrantel Pamoate + Sarolaner3,386
Sarolaner58
Sarolaner + Selamectin152
Selamectin158
Sulfadimethoxine22

The openFDA records give the value "MSK" for the brand name and for the manufacturer name of each drug. FDA says that MSK means "masked". So the site cannot count a report for a brand. A report can name more than one drug.

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.

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. Source: Adverse Event Reports for Animal Drugs and Devices

Ingredients, all combinations

The list has every active ingredient with 20 or more reports that list this sign, in order of name. It has 23 ingredients.

Reports by species

The share is of the 14,372 reports that list this sign. The sign is in 1.4% of all reports about the species dog. The sign is in 0.4% of all reports about the species cat.

Reports by month and by year

Reports for each month, Jul 2021 to Jun 2026. The month is the month in which FDA received the report.

FDA says that a report can take 3 to 6 months to reach the public data. The newest months can get more reports in a later update.

Reports that list Lack of efficacy (endoparasite) - roundworm NOS, by the year in which FDA received them
YearReports
20261,001
20252,017
20242,172
20231,928
20221,691
20211,876
20201,587
20191,059
2018878
20177
201621
201525
201429
20139
201210
201111
20105
20095
20084
20072
20062
20051
20043
20034
20022
20012
200014
19997

What these reports record

Outcome at the time of the report

  • Reports with this sign
  • All reports
  • Recovered/Normal4.4%632
  • Recovered with Sequela[recovered, with a lasting effect]under 0.1%7
  • Ongoing47.8%6,869
  • Died0.2%35
  • Euthanized0.1%15
  • Outcome Unknown47.2%6,788

An outcome in a report is not proof that the drug caused it. The person who sends the report gives the outcome. Each share is of the 14,372 reports that list this sign.

Age of the animal

  • Reports with this sign
  • All reports
  • Under 1 year21.3%3,058
  • 1 to 3 years30.1%4,322
  • 4 to 7 years22.9%3,291
  • 8 to 11 years16.6%2,380
  • 12 years and over6%865
  • Age not given3.2%456

The outcome is for the full report, not for this sign only.

Next in the A to Z list of signs

All clinical signs

Cite this page

Pet Drug Reports. Lack of efficacy (endoparasite) - roundworm NOS: adverse event reports for animal drugs. https://petdrugreports.com/reaction/lack-of-efficacy-endoparasite-roundworm-nos/ Source: FDA Center for Veterinary Medicine, openFDA Animal and Veterinary adverse event reports, export of . Reports received through .

Where the data come from

The counts come from the openFDA Animal and Veterinary adverse event files, export of 30 Oct 2026. The files have the reports that the FDA Center for Veterinary Medicine received through 26 Jun 2026. The files mask brand and manufacturer names. The site counts a drug by the active ingredients that each record gives, and gives no count to a brand, an application or a company. Ingredient names and the lists of approved products follow the FDA Green Book of 2 Nov 2026. The site counts the different spellings of one VeDDRA term together.

The site does not publish report text, lot numbers or details of a reporter. FDA's record is the authority. See how the site counts reports, the data sources and the corrections page.

Questions about this sign

What does this term mean in a report?

In plain words: the product did not have the expected effect: roundworms. It is a term from VeDDRA, the list of terms that FDA and drug companies use to code a report. The person who coded the report selected the term.

How does the count of the latest 12 months compare with the 12 months before?

FDA received 1,864 reports in the 12 months to June 2026. It received 2,109 reports in the 12 months before. FDA says that a report can take 3 to 6 months to reach the public data. The newest months can get more reports in a later update.

How many of these reports have a serious flag?

Of the 14,299 reports that say if the event was serious, 42.6% have the serious flag. The person who sends a report sets the flag.

Does a drug in the table cause this sign?

The reports do not show that. A report can name more than one drug. FDA states this about the data.

When looking at the results, be aware that there is no certainty that the reported drug or device caused the adverse event.

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. Source: Adverse Event Reports for Animal Drugs and Devices