FOI release

FOI2025/00057 – Apoquel side effects

Published 5 February 2026

1. FOI2025/00057 Request

Information regarding the incidence of neoplasia related side effects with Apoquel.

The number of cases and ideally whether the animal had any pre-existing skin masses.

2. Our reply

The following Apoquel products are currently authorised in the UK:

• Apoquel 3.6mg Film-coated Tablet for Dogs
• Apoquel 5.4mg Film-coated Tablet for Dogs
• Apoquel 16mg Film-coated Tablet for Dogs
• Apoquel 3.6 mg Chewable Tablets for Dogs
• Apoquel 5.4 mg Chewable Tablets for Dogs
• Apoquel 16 mg Chewable Tablets for Dogs

All adverse event reports in the VMD database have their clinical signs coded using the Veterinary Dictionary for Drug Regulatory Activities (VeDDRA).

We have provided below the number of adverse event reports containing a clinical sign in the neoplasia System Organ Class (SOC). SOCs are one of the hierarchical levels of VeDDRA. Please be aware that one animal may have more than one clinical sign belonging to the same SOC, and therefore the total number of occurrences of clinical signs will be greater than the total number of animals reacted.

We have 858 reports which contain one of the Apoquel products listed above and at least one VeDDRA belonging to the Neoplasia SOC.

You requested to know if any of these animals had any pre-existing skin masses. There is no specific field in our database to identify cases with pre-existing conditions, as VeDDRA codes are only used for adverse events that occurred after product administration, and this information is not always provided when reporting.

To manually review each of the reports for pre-existing condition would exceed the cost limit for a Freedom of Information Act request. However, we used the search term ‘pre-existing’ on all the available data, and identified the following reports with pre-existing skin masses. Please be aware that this may not reflect all the cases with pre-existing skin masses in the database:

• 1 report with progression of pre-existing warts
• 4 reports with progression of pre-existing fatty lumps or lipomas
• 1 report with progression of a pre-existing liposarcoma
• 6 reports with pre-existing papilloma which then developed further papilloma
• 4 reports with progression of pre-existing squamous cell carcinoma
• 3 reports with progression of a pre-existing histiocytoma
• 1 report of progression of a pre-existing mast cell tumour
• 1 reporting progression of pre-existing masses, no details
• 1 report of pre-existing interdigital cysts that became swollen and burst
• 1 report of pre-existing lesion/cyst at tail base, diagnosed with a round cell tumour

The number of adverse event reports includes reports: 

• where more than one product was used
• when the product was used off-label, that is using a medicine in a way that is not specified on the product’s label, including prescribing of unauthorised medicines following the cascade
• where the reporters, medical professionals or MAH did not consider an association between the product administration and the adverse event to be likely
• where, on further evaluation, there were other reasons for the adverse event occurring such as underlying illnesses or an alternative cause for the clinical signs seen

Evaluation of adverse event reports is dependent on the accuracy and quality of data received within adverse event reports from veterinary professionals and animal owners. 

Although adverse event report information can be useful to provide a general overview of a veterinary medicinal product (VMP), it is important for any clinical decisions regarding the use of a VMP to be based on a risk/benefit discussion specific to the animal or group of animals being administered the VMP. An overall frequency of an adverse event occurring for a VMP does not reflect the actual risk for an individual animal, as there are many individual factors that may contribute to the likelihood of an adverse event occurring. 

Data published by the VMD are not subject to independent verification and the VMD does not guarantee their accuracy. Figures may be different to those provided by different regulatory authorities, pharmaceutical companies, and other authorities within the United Kingdom. 

All medicines whether for human or animal use come with risk, and the benefits of use in wider populations need to outweigh the potential risks. Information on adverse events that have been known to occur following administration of a particular product are summarised in sections 3.6/4.6 of the Summary of Product Characteristics (SPC). 

The SPC is a document describing the properties and the officially approved conditions of use of a medicine. The SPC and associated product information are updated as new information is available, and the latest version of an SPC can be found on our publicly available Product Information Database. It is important for veterinary professionals to ensure that this information is reviewed, and any risks discussed with the animal owner or keeper, prior to administering the product. A rolling 6-month list of Summary of Product Characteristic (SPC) changes for veterinary medicines can be found on the monthly medicines update page Vet practice & supply. 

The SPCs for both film-coated and chewable Apoquel list the following adverse events:

Very common (>1 animal / 10 animals treated):

pyoderma, skin lump, papilloma

Common (1 to 10 animals / 100 animals treated):

lethargy, lipoma, polydipsia, increased appetite nausea, vomiting, diarrhoea, anorexia histiocytoma, fungal skin infection, pododermatitis otitis lymphadenopathy cystitis aggression

Very rare (<1 animal / 10,000 animals treated, including isolated reports):

anaemia, lymphoma, convulsion

The SPCs also include the following warnings:

4.5 Special precautions for use

i) Special precautions for use in animals

Oclacitinib modulates the immune system and may increase susceptibility to infection and exacerbate neoplastic conditions. Dogs receiving the veterinary medicinal product should therefore be monitored for the development of infections and neoplasia.

Pharmacovigilance updates are published on gov.uk at https://www.gov.uk/guidance/urgent-safety-updates-for-veterinary-medicines; this also includes any updates involving non-veterinary medicines used in animals. To receive these pharmacovigilance updates via email, please click on the ‘Get emails about this page’ button.