FDA Updates Solensia Safety Labelling for Cats, Strengthening Adverse-Event Communication

US Food and Drug Administration (FDA) has updated the safety-related labelling for Solensia (frunevetmab injection), a monoclonal antibody used to control pain associated with osteoarthritis in cats. The update, recorded last week in the FDA’s Animal Drug Safety-Related Labeling Changes database, adds a post-approval adverse-event section, strengthens instructions for discussing risks with cat owners, and introduces a dedicated Client Information Sheet.

The change is significant for veterinary practice because it formalises how safety information should be communicated before each injection. It is not, on its own, an announcement that Solensia has been withdrawn, that its approved indication has changed, or that the FDA has established a definitive causal relationship between the medicine and every event reported after marketing.

What is Solensia?

Solensia contains frunevetmab, a feline monoclonal antibody that binds to nerve growth factor (NGF), a protein involved in transmitting pain signals. The treatment is indicated for control of pain associated with osteoarthritis in cats and is administered by a veterinarian as a subcutaneous injection, generally once a month. It is intended to relieve pain; it does not reverse or cure the underlying progression of osteoarthritis.

Osteoarthritis can impair a cat’s mobility and daily activities, while behavioural changes may make chronic pain difficult for owners to recognise. A treatment administered at monthly veterinary visits also places particular importance on ongoing review: clinicians need to assess the animal’s response, discuss new symptoms and reconsider the benefit-risk balance before continuing therapy.

What changed in the FDA label?

The FDA lists four main changes:

1. Updated dosage and administration instructions: veterinarians are directed to provide the Client Information Sheet and discuss potential adverse drug events with the owner before each injection.

2. A new “Post-Approval Experience” subsection: adverse events reported after marketing are described in the Adverse Reactions section.

3. A new “Information for Cat Owners” section: the label directs veterinarians to discuss the information sheet and relevant potential reactions before administration.

4. A dedicated Client Information Sheet: owners receive written information about potential adverse reactions, risk considerations and when to contact their veterinarian.

These changes place greater emphasis on documented owner communication, rather than relying solely on the veterinarian’s knowledge of the package insert or on informal counselling.

Adverse events listed in post-approval reporting

The FDA’s revised label groups reported events by body system. The listed categories include:

The FDA also states that deaths, including euthanasia, have been reported as outcomes in some cases involving the listed adverse events.

These reports require careful interpretation. The FDA explicitly cautions that not all adverse events are reported to the agency and that post-approval reports do not necessarily allow reliable calculation of event frequency or confirmation of a causal relationship to exposure.

Spontaneous adverse-event reporting is an important pharmacovigilance tool because it can identify patterns that merit further investigation after a product enters wider clinical use. However, reports alone do not establish incidence: the number of treated animals, completeness of reporting, underlying illnesses, concurrent treatments and other factors affect interpretation.

What cat owners should know

The new Client Information Sheet is intended to support a discussion with the veterinarian before each injection. The FDA advises owners to contact their veterinarian if they observe signs such as severe itching, balance problems, difficulty walking or jumping, weakness, seizures, increased drinking or urination, vomiting, diarrhoea, or other concerning changes. Serious adverse reactions can occur, and the label warns that some reported outcomes have involved death or euthanasia.

Owners should also discuss their cat’s medical history, including skin conditions, neurological signs, kidney disease, pancreatic disease and previous allergic reactions. They should tell the veterinarian about all medicines and supplements the cat receives and disclose any previous or current monoclonal-antibody therapy.

The information sheet does not replace individual veterinary advice. Owners should not independently change treatment or assume that a symptom is caused by Solensia without clinical assessment. Equally, new or worsening symptoms should not be dismissed simply because the cat has an established diagnosis of osteoarthritis.

Implications for veterinary clinics and the companion-animal industry

Veterinary practice and documentation: The instruction to provide and discuss the information sheet before every injection creates a clear workflow requirement. Clinics may need to review appointment protocols, owner handouts, consent documentation and staff training to ensure the discussion occurs consistently.

Pharmacovigilance: The expanded post-approval section makes it easier for clinicians and owners to understand which types of events have been reported. Veterinarians should document suspected reactions and use the applicable manufacturer and FDA reporting channels. Reports should include relevant clinical history, timing, concurrent treatments and outcomes wherever possible.

Product communication and trust: Biologic therapies can offer a useful treatment option, but clear communication about both potential benefits and risks is essential. Written information can improve consistency between clinicians and help owners recognise when follow-up is warranted. The update also underscores the importance of keeping clinic-facing and owner-facing materials aligned with the latest approved labelling.

Commercial and regulatory monitoring: The FDA notes that updated labels may not appear immediately on every product package because existing inventory can remain in distribution. It advises veterinarians to contact the sponsor for the most current product labelling. Clinics should therefore check current official materials rather than assume that every physical package insert has already incorporated the change.