Solensia (frunevetmab) is the first and only FDA-approved monthly injection for osteoarthritis pain in cats.

Solensia (frunevetmab injection) is the first FDA-approved monoclonal antibody for any animal species and the only approved treatment specifically for osteoarthritis pain in cats. Approved by the FDA in January 2022 and developed by Zoetis, it is given once monthly as a subcutaneous injection in the veterinary clinic. This article covers how Solensia works, what the clinical studies found, dosing, safety — including what is known about use in cats with chronic kidney disease — side effects, and how it compares to the pain management options that existed before it.

Why feline OA pain has been undertreated

Feline osteoarthritis is far more common than most cat owners realize. Studies have found radiographic evidence of OA in 61% of cats over age 6 and up to 90% of cats over age 12. Yet it is dramatically underdiagnosed, because cats mask pain as a survival behavior. Unlike dogs, who limp or vocalize, arthritic cats show subtle behavioral changes: reduced jumping, decreased grooming, reluctance to use stairs, soiling outside the litter box, withdrawing from interaction.

Before Solensia, long-term OA pain management in cats was limited. The two NSAIDs approved for cats in the US — meloxicam (off-label chronic use) and robenacoxib (Onsior, approved for short-term postoperative use) — carry risks of kidney and gastrointestinal injury with prolonged use. Most cats with OA are seniors who also have chronic kidney disease (CKD), making long-term NSAID use a balancing act between pain relief and renal safety. Gabapentin is widely used off-label but lacks FDA approval for pain in cats and can cause sedation.

Solensia addresses this gap by using a mechanism that does not depend on kidney or liver metabolism. As a monoclonal antibody — a protein — it is broken down through normal protein catabolism pathways rather than through cytochrome P450 enzymes or renal clearance.

How Solensia works: targeting nerve growth factor

Frunevetmab is a cat-specific monoclonal antibody that binds to nerve growth factor (NGF). NGF is a protein produced in joints affected by osteoarthritis. It activates pain receptors (TRPV1) and perpetuates the pain signal by increasing release of additional pain and inflammatory mediators. When frunevetmab binds to NGF, it prevents NGF from activating those receptors, reducing the pain signal reaching the brain.

This mechanism is different from NSAIDs, which reduce inflammation by blocking cyclooxygenase (COX) enzymes throughout the body — including in the stomach lining, kidneys, and intestinal tract. By targeting a single pain pathway, Solensia avoids the broad systemic effects that make NSAIDs risky for long-term use in cats with kidney disease.

NGF blockade has been explored in human medicine but development was slowed by concerns about accelerating OA progression in some human trials. The FDA's approval of Solensia for cats was based on demonstrated pain control with a safety profile acceptable for the feline indication.

What the field studies showed

The FDA approval was supported by two randomized, controlled field studies in client-owned cats with osteoarthritis. The primary endpoint was the Client Specific Outcome Measure (CSOM), where owners rated whether their cat's pain had improved.

In a 3-month field study cited by Zoetis, 77% of cat owners reported improvement in signs of pain when their cats were treated monthly with Solensia, compared with 67% in the placebo group. The difference between treatment and placebo was statistically significant, though the placebo response rate highlights the challenge of subjective pain assessment in cats.

The FDA Freedom of Information summary (NADA 141-546) notes that while individual study results varied, "the weight of the evidence from these two studies demonstrates substantial evidence of effectiveness of Solensia for the control of pain associated with osteoarthritis in cats."

A separate pilot clinical study published in Frontiers in Veterinary Science (2021) evaluated 126 client-owned cats with a mean age of 12–13 years. Roughly half the cats had CKD stage II by virtue of age alone. The study supported both efficacy and tolerability in this population.

What improvement looks like in practice. Owners and veterinarians report changes including:

Resuming jumping onto furniture or counters
Improved grooming behavior
Increased social interaction and play
More willing use of the litter box (particularly if arthritis had made high-sided boxes difficult)
Greater activity and willingness to climb stairs

Zoetis and most veterinary pain specialists recommend evaluating the initial response after 2–3 monthly injections, because steady-state drug levels are achieved after approximately two doses. Some cats show improvement after the first injection; others need longer.

Dosing: weight-based, clinic-administered

Solensia is dosed by weight and administered by a veterinarian as a subcutaneous injection once every 4 weeks. Each vial contains 7 mg/mL of frunevetmab.

Cat weight	Volume	Number of vials
5.5–15.4 lb (2.5–7 kg)	1 mL	1 vial
15.5–30.8 lb (7.1–14 kg)	2 mL	2 vials

Cats over 15.4 lb receive the contents of two vials withdrawn into a single syringe. The target dose is a minimum of 0.45 mg/lb (1 mg/kg) body weight per month.

Solensia is not available for at-home administration. It is prescription-only and must be given in the clinic because professional expertise is required for proper diagnosis, dose calculation, injection, and monitoring of adverse reactions.

Pharmacokinetic data show peak plasma levels at 3–7 days after injection, with a half-life of approximately 10 days. Steady state is reached after two monthly doses.

Safety and side effects

The label lists the following based on field studies (182 Solensia-treated cats and 93 controls):

Adverse reaction	Solensia (%)	Control (%)
Vomiting	13.2	10.8
Injection site pain	10.9	14.0
Behavioral changes	7.1	6.5
Diarrhea	6.6	5.4
Renal insufficiency	6.6	4.3
Anorexia	6.6	4.3
Lethargy	6.0	3.2
Dermatitis	6.0	1.1
Alopecia	5.5	2.2
Dehydration	4.4	0.0
Pruritus	3.8	0.0
Scabbing on head/neck	3.3	1.1

Most of these events occurred at rates close to the placebo group. Vomiting and injection site pain were the most common but were not statistically significantly different from controls. Dermatitis, pruritus, and scabbing on the head and neck were more notable in the treatment group and are listed in the label's adverse events section.

The prescribing information includes these contraindications and cautions:

Do not use in cats with known hypersensitivity to frunevetmab.
Do not use in breeding, pregnant, or lactating cats. Anti-NGF monoclonal antibodies caused fetal abnormalities, increased stillbirths, and increased postpartum fetal mortality in rodent and primate studies.
Do not use in cats under 12 months of age or under 2.5 kg (5.5 lb).
Concurrent NSAIDs: The safe use of Solensia with concurrent NSAIDs has not been studied in cats. Tell your veterinarian about all medications and supplements.
Concurrent monoclonal antibodies: Safe use with other mAbs (e.g., Librela for dogs — bedinvetmab, another anti-NGF product) is not known, though Solensia is a cat-only product.

Solensia and kidney disease

This is the question most cat owners ask, because the overlap between feline OA and CKD is substantial. The key points from the label and published literature:

Solensia is not processed by the kidneys or liver. As a monoclonal antibody (protein), it is degraded through normal protein catabolism into peptides and amino acids. It does not interact with cytochrome P450 enzymes.
The field studies included cats with early-stage CKD (IRIS stages 1 and 2). In the pilot study, approximately half of enrolled cats had CKD stage II. The majority tolerated Solensia without clinically significant changes in kidney values.
Twelve cats in the field study (6.6% of the treatment group) showed evidence of worsening renal insufficiency on lab work. Four cats in the placebo group (4.3%) also showed renal changes. This difference was small and may reflect the natural progression of CKD in senior cats rather than a drug effect.
The label notes: "The safety and efficacy of this product has not been investigated in cats with kidney disease IRIS stages 3 and 4." For cats with advanced CKD, the decision should involve a direct conversation with the veterinarian about risk versus benefit.

In overdose studies, healthy cats given Solensia at 5× the maximum recommended dose for six consecutive months showed no clinically significant changes on physical exam, lameness evaluation, or body weight.

What Solensia does not do

It does not cure or reverse osteoarthritis. OA is a progressive degenerative disease. Solensia controls the pain signal; it does not repair cartilage.
It does not replace a multimodal approach. Environmental modification (ramps, low-sided litter boxes, padded bedding), weight management, and joint-support diets remain important components of feline OA management.
It does not replace diagnostic work. Before starting Solensia, a veterinarian should confirm that the cat's signs are consistent with OA and not caused by another condition (hyperthyroidism, diabetes, neurologic disease, or neoplasia) that could mimic or contribute to pain behaviors.

Solensia versus NSAIDs and other options

Feature	Solensia (frunevetmab)	NSAIDs (meloxicam, robenacoxib)	Gabapentin (off-label)
FDA-approved for feline OA pain	Yes	No (robenacoxib is post-op only; meloxicam chronic use is off-label)	No
Mechanism	Anti-NGF monoclonal antibody	COX enzyme inhibition	Calcium channel modulation
Route	Subcutaneous injection (clinic)	Oral (home)	Oral (home)
Frequency	Monthly	Daily to every other day	Daily to BID
Kidney metabolism	No	Yes — NSAIDs reduce renal blood flow	Partially renal excretion
GI risk	Minimal	Significant with long-term use	Low
Sedation	No	No	Yes, common
Cost	Higher per dose ($50–100/month)	Lower per dose	Lower per dose

Solensia is not necessarily a replacement for all other pain medications. In some cats, a multimodal approach combining Solensia with environmental changes, weight optimization, and occasionally low-dose adjunctive medications provides the best outcome. The decision should be made with the attending veterinarian based on the cat's full clinical picture.

What to ask your veterinarian

"My cat is slowing down and not jumping as much — could this be OA pain?"
"Is Solensia safe for my cat's stage of kidney disease?"
"How many injections should we try before deciding if it's working?"
"Should we do blood work before starting Solensia?"
"Are there environmental changes we should make at the same time?"

Cost

A single monthly Solensia injection typically costs $50–100 per dose, depending on the practice and geographic area. At that range, annual cost runs approximately $600–1,200. Some pet insurance plans cover Solensia when prescribed for a diagnosed condition; check with your insurer before starting. Zoetis also offers a rewards program that may offset cost for eligible clients.