Librela™ (for dogs) and Solensia™ (for cats) are new drugs used by veterinarians to relieve the pain of osteoarthritis (OA). Since these drugs were approved in Europe (2020) and the US (2023), veterinarians have been reporting that Librela™ and Solensia™ show good results. Unfortunately, the safety of these drugs has come into serious question in recent months, primarily due to reported adverse reactions. Furthermore, the long-term safety and efficacy of these drugs is still unknown.
What are Librela™ and Solensia™?
Librela™ contains the active substance bedinvetmab, which is a monoclonal antibody. Monoclonal antibodies are artificially created antibodies that are designed to bind to a specific protein in the body. In the case of Librela™, bedinvetmab is designed to bind to nerve growth factor (NGF), a protein involved in pain signaling. Canine proteins are used to create the antibodies. Solensia™ is the brand name for the cat-specific monoclonal antibody called frunevetmab. It also binds to nerve growth factor and targets the body’s pain signals, preventing the signals from working. Feline proteins are used in the manufacture of Solensia™. Both drugs are administered via a monthly injection.
In drug trial studies, Librela™ was shown to improve mobility and overall quality of life. Monoclonal antibodies have been hailed as a breakthrough in the treatment of arthritis in dogs and cats. Zoetis, the manufacturer of Librela™ and Solensia™, states that it does not pose a risk of toxicity to the liver, kidney, or heart versus other current arthritis medications (such as NSAIDS) that have that potential. Librela™ was granted marketing authorization by the European Medicines Agency (EMA) in 2020 and has been used by veterinarians in Europe since 2021 as a treatment option for OA pain in dogs. In two field studies, dogs administered Librela™ demonstrated a reduction in OA pain compared to dogs that received the placebo. However, understanding the results of these field studies is essential when considering the use of the drug.
What are the known side effects of Librela™ and Solensia™?
Librela™ offers significant pain relief for dogs with arthritis, improving their quality of life and overall well-being. However, it is important to consider the pros and cons of pet safety and efficacy when using Librela™. While it provides pain relief, it also carries the potential for side effects and risks, especially in older dogs with more than just osteoarthritis.
Like any pharmaceutical, Librela™ has side effects. The most common are:
- Injection site reactions/pain
- Lethargy
- Drooling
- Shaking
- Behavior changes
- Hiding
- Increased or decreased thirst
Other more serious side effects that have been reported include[1]:
- Neurological problems – hind-end weakness, inability to walk, unsteady on their feet (ataxia)
- Hypersensitivity-like reactions such as facial swelling and other allergic reactions, bacterial infection, dermatitis, rash
- New or worsened seizures
- Renal and urinary tract disorders, such as urinary incontinence or infection
- Anorexia
Solensia™ was launched several years before Librela™, and therefore, a peer-reviewed adverse event paper has been published[2]. In this study, side effects were limited to dermatological issues including:
- Moderate to severe pruritus (scratching) resulting in self-trauma to the neck and/or head
- Superficial dermatitis
- Alopecia (hair loss)
- Ulcerations of the skin secondary to self-trauma
- Reactions at the injection site
- Eczema
Zoetis, the company that created Librela™ and Solensia™, is defending the safety and efficacy of its drugs following concerns raised by the Wall Street Journal article reviewing Librela™[3]. Pet owners reported instances where their animals experienced adverse reactions to these drugs, including cases where animals became sick rather than showing improvement in their conditions. Pet owners are blaming the drug for causing a rapid decline in their dogs, including weight loss, urinary tract infection, and other related issues. The company states that the reported side effects are relatively rare (less than 1%). However, keep in mind that it is thought that less than 1% of adverse events are reported to manufacturers and the FDA. More serious side effects have been reported in dogs with comorbidities of chronic disease such as kidney disease, neurological issues, or cancer. The drug has not been studied in dogs with other health problems or comorbidities, only in dogs with osteoarthritis.
What is not yet known about Librela™ and Solensia™?
Because there are no real long-term studies about the side effects of Librela™ and Solensia™, there are many outstanding questions about the long-term consequences of these drugs. The following questions/factors are a start but by no means exhaustive.
- Neurological side effects: Nerve growth factor (NGF) is involved in the inflammatory process and plays a role in regulating inflammation. Certain nerves depend on NGF for survival and maintenance – if the antibodies in Librela™ and Solensia™ bind up NGF to reduce pain, these drugs could negatively influence the growth of nerves. This may be why one of the side effects of these drugs are seizures and weakness. If there is a sudden loss of NGF due to it being bound up by the antibodies of Librela™, there may be a dramatic increase in inflammation due to the loss of this neurotrophin. This effect may also influence movement difficulty, weakness, and seizures.[4]
- Immunogenicity is defined as the “ability of a foreign substance, such as an antigen, to provoke an immune response in the body of a human or other animal. The response may be wanted or unwanted."[5] All therapeutic protein products, including monoclonal antibodies, have the potential for inducing a negative immune response following administration. There are very real possibilities that “antidrug antibodies” could form resulting in potentially adverse effects. As of the writing of this blog, we have no information for whether or when this may happen. We also do not know the ramifications of this occurring, although in some cases it has led to severe immune reactions (fatal anaphylaxis, chronic autoimmune conditions, etc.)
- Long-term effects: The Librela™ package insert states that “Long-term effects which may occur more than 9 months after the use of Librela™ have not been evaluated.[6]” Pet parents need to compare the benefits against the potential harmful effects of this drug. The term “long-term study” means different things to different companies, researchers, veterinarians, and pet parents. In my opinion, we do not yet know the long-term effects of these drugs.
- Organ damage: The Librela™ package insert states that “NGF is expressed within the heart and vasculature, and the long-term effects of reduced NGF in dogs with cardiac disease are unknown.” NGF is not only vital to the functioning of the heart and blood vessels - blocking it can disrupt every major system and organ[7]. Anywhere that NGF is expressed in the body is at potential risk of damage. As a result, we currently do not know the specific cardiac effects of these drugs, or whether there is potential harm to the central nervous system, including a risk of cognitive decline.
- Many other unanswered questions: Does this drug have any effect on vaccinated pets? Can dogs and cats with underlying kidney or neurological issues be at a higher risk of adverse effects from these drugs? What comorbidities put an animal at risk when taking these drugs? Does age or breed matter? These unanswered questions are just a few examples.
Are there alternative treatments to consider?
Yes! There are a variety of treatments available and may include:
- Physical therapy, massage/manual therapy
- Weight management – particularly in obese dogs and cats. Over 50% of pets in the US are overweight!
- Acupuncture
- Cold laser therapy
- Pulse magnetic therapy (PEMF)[8]
- Food therapy – a species-appropriate whole foods diet is always recommended to minimize inflammation and support the joints.
- Supplements such as deer antler velvet, glucosamine and chondroitin, fish oil, SAMe, and turmeric help support joints and reduce inflammation.
- Chinese herbal formulas that reduce inflammation and provide joint support as well as pain control.
- Conventional veterinary medicine has been using nonsteroidal anti-inflammatory drugs (NSAIDS) for decades for animals suffering from OA. However, dogs and cats often do not respond well to these medications or have adverse reactions to them. Other conventional treatment options include use of pain medications in combination, such as gabapentin and amantadine. Adequan injections that supply polyglycosaminoglycans, the building blocks of cartilage and joint fluid, are another option. With any drug, there are potential side effects which must be weighed against the benefits.
Veterinarians should always use caution when prescribing Librela™ and Solensia™. Pain management is very important when considering quality of life, but it is essential to consider the potential risks and side effects of these drugs; veterinarians should discuss them with their clients. Pet owners need to be proactive in discussing their pet’s medical history and any concerns before starting treatment. As relatively new drugs, there are many unanswered questions regarding their safety. The true test of a drug’s safety and effectiveness comes when the drug becomes widely used through its availability in the marketplace. Unfortunately, time must pass and additional studies need to be conducted before these drugs are no longer considered “spooky.”
[1] https://www.fda.gov/animal-veterinary/cvm-updates/fda-approves-first-monoclonal-antibody-dogs-osteoarthritis-pain
[2] https://www.fda.gov/media/178956/download?attachment
[3] https://www.wsj.com/health/pharma/dog-cat-arthritis-drugs-bcdddea6
[4] https://www.realmushrooms.com/solensia-cats-librela-dogs-side-effects/
[5] https://drjosie.substack.com/p/librela
[6] https://www.zoetisus.com/content/pages/Products/Dogs/Librela/Resources/documents/Librela-prescribing-information.pdf
[7] https://petadvocare.com/
[8] https://vcahospitals.com/know-your-pet/pulsed-electromagnetic-field-therapy
