FOI release

EIR2026/00678 - Fipronil and Imidacloprid: Post-Authorisation Safety Signals

Published 13 July 2026

1. Your request

Background to this request  

Under the Veterinary Medicines Regulations 2013 (as amended by the Veterinary Medicines (Amendment etc.) Regulations 2024), Marketing Authorisation Holders (MAHs) are required to operate a pharmacovigilance system that includes the monitoring of scientific literature as a source of safety signals. Specifically, MAHs must identify, assess, and report to the VMD any signals arising from published literature - including information relevant to human health, environmental risk, and antimicrobial or antiparasitic resistance - as part of their Benefit-Risk Submission Reports (BRSRs), signal notifications, and previously via Periodic Safety Update Reports (PSURs).  

My request  I would like to request the following information in relation to companion animal parasiticide products authorised in the UK containing the active substances fipronil and/or imidacloprid:  

1. Copies of, or summaries of the content of, any signal notifications submitted by MAHs to the VMD that were identified from or supported by published scientific literature, relating to:    a. Human health risks (including handler/owner exposure, dermal or systemic toxicity, endocrine disruption, or other human safety concerns);    b. Environmental risk (including aquatic toxicity, ecotoxicological effects on non-target invertebrates, or detection in surface waters or soil);    c. Resistance and treatment failure (including any published evidence of reduced susceptibility, confirmed resistance, or mechanisms of resistance in target parasite species — in particular Ctenocephalides felis and Ctenocephalides canis — to fipronil or imidacloprid).  

2. Any communications between the VMD and MAHs (including requests for further information or regulatory actions taken) arising from the signal notifications described at (1) above.  

3. Whether the VMD has itself identified any signals relating to fipronil- or imidacloprid-containing companion animal parasiticides from published scientific literature, independently of MAH submissions, and if so, any documentation of how those signals were assessed and acted upon.  

4. Whether any BRSRs (or prior PSURs) submitted by MAHs for fipronil- or imidacloprid-containing companion animal parasiticides have included literature references in relation to the risk categories listed at (1)(a)–(c) above, and if so, a summary or index of those references.  

Scope and format  

If any part of this request would exceed the appropriate cost limit under s.12 of the FOIA, I would welcome guidance on how to prioritise, and I would ask that the VMD consider whether the Environmental Information Regulations 2004 (EIR) apply to any part of this request relating to environmental risk — under which a cost limit does not apply in the same way.  

If any requested information is considered exempt, I ask that you identify which exemption applies and whether, in your view, the public interest favours disclosure — given the ongoing public and regulatory debate about the presence of fipronil and imidacloprid in UK waterways and the environmental risk posed by companion animal parasiticides.  

I would prefer to receive the response by email. If original documents cannot be provided in full, summaries or redacted versions, or a schedule of documents held, would be welcome.  

I confirm that this request is being made under the Freedom of Information Act 2000 and/or the Environmental Information Regulations 2004 as applicable.

2. Our reply

Your requests 1, 2 and 4 are very broad as it does not specify a time parameter and references substances used in over 300 currently authorised products.  

As you correctly noted, benefit-risk reports (BRRs) came into effect with the introduction of the new Veterinary Medicines Regulations (VMRs) from May 2024. Prior to these changes, Marketing Authorisation Holders (MAHs) were not required to submit BRRs; instead, they were required to submit Periodic Safety Update Reports (PSURs), produced under the previous regulatory framework.  

We have searched the BRRs and signal notifications we hold since May 2024 for the information requested, which are held in a searchable format, and found no records that were identified from or supported by published scientific literature.  

While PSURs are held by the VMD, the information you have requested is not held in a way that allows it to be readily retrieved. The reports are not categorised or searchable by the specific parameters set out in your request. 

To provide the requested information, we would need to manually examine each individual PSUR to identify whether it contains relevant information. Given the volume of reports involved and the detailed nature of the review required, this would take a substantial amount of staff time. For this reason, we are unable to provide all the requested information as it is currently framed. 

We therefore consider that these elements of your request are manifestly unreasonable under regulation 12(4)(b) of the Environmental Information Regulations 2004. 

In applying regulation 12(4)(b), we have considered the public interest in disclosure. We recognise the importance of transparency and openness in relation to environmental information. However, this must be balanced against the public interest in ensuring that public authorities are able to carry out their regulatory functions effectively and make best use of limited resources. 

For question 3, independently of marketing authorisation holder submissions, the VMD has identified evidence relating to fipronil and imidacloprid‑containing companion animal parasiticides through published scientific literature and environmental monitoring data. These are not pharmacovigilance signals, but evidence relating to environmental exposure and contamination pathways. 

This includes VMD‑funded, peer reviewed studies published between 2024 and 2025, which demonstrated that topical flea and tick spot‑on treatments can contribute to environmental residues via wastewater pathways and when treated dogs swim. 

This evidence was assessed through the cross‑government Pharmaceuticals in the Environment (PiE) Group, chaired by the VMD, and has informed subsequent actions, including publication of a PiE roadmap to address the environmental concerns, a review of the appropriateness of the distribution categories of these products, and support for an international review of environmental risk assessment methodologies for companion animal parasiticides. 

Further evidence gathering has been undertaken to inform future policy and regulatory decisions. While the aforementioned VMD‑funded studies have confirmed that topical flea and tick spot‑on treatments can contribute to environmental residues of fipronil and imidacloprid via wastewater pathways and when treated dogs swim, important evidence gaps remain.  

These include the contribution of non‑veterinary sources, ecological impacts at current concentrations, potential animal and human health risks associated with changing usage patterns, and the need for baseline data to measure behavioural change. To address these gaps, the VMD is funding further research, including exposure modelling, behavioural studies, a national pet owner survey, and additional research through the University of Plymouth.

2.1 How we can help you refine your request

In accordance with regulation 9 of the EIR, we would be happy to consider a refined request if you are able to narrow the scope, for example by limiting the timeframe, specifying particular products, or identifying specific environmental issues of interest. This may enable us to determine whether any relevant information can be provided.