Reaction profile
The FDA adverse-event record for lack of efficacy (roundworm)
2,765 FDA adverse-event reports reference lack of efficacy (roundworm) (VeDDRA 2656). See the species, breeds, and drugs most associated with it below.
- 2,765
- reports citing this reaction
- 0.5%
- death-coded share
- Dog
- most-affected species
- Milbemycin Oxime + Praziquantel
- most-associated drug
Species Most Affected
Breeds Most Affected
Associated Drugs
Lack of efficacy (roundworm) Reaction Insights
2,765 reports name Lack of efficacy (roundworm); 13 recorded a death outcome (0.5% of reported events, not a population-level mortality rate). VeDDRA code: 2656.
By species: Dog (2,685 reports), Cat (59 reports), Cattle (16 reports). By breed: Retriever - Labrador (519), Retriever - Golden (226), Crossbred Canine/dog (129).
Most co-reported drugs: Milbemycin Oxime + Praziquantel (1,286 reports), Ivermectin + Pyrantel As Pamoate Salt (624 reports), Milbemycin Oxime + Spinosad (337 reports), Lufenuron + Milbemycin Oxime (236 reports).
Read these counts as reporting volume, not risk: per our methodology, co-reporting reflects temporal association captured in voluntary submissions, not proof that a drug caused this reaction. A widely-prescribed drug will rack up more raw co-reports at an identical true rate than a rarely-used one, so compare within similar-exposure products.
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.