Humira for dogs: Dosage and safety

In this article:

• What is Humira used for in dogs?
• Is Humira safe for dogs?
• Humira alternatives for dogs
• Summary

In this article

• What is Humira used for in dogs?
• Is Humira safe for dogs?
• Humira alternatives for dogs
• Summary

Humira (adalimumab) is an injected monoclonal antibody that blocks the immune system. Healthcare professionals prescribe it to treat various autoimmune conditions in people, including rheumatoid arthritis, psoriasis, and inflammatory bowel disease. Dogs can get some of the same autoimmune conditions, but veterinarians do not use human biologic drugs like Humira to treat these conditions.

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What is Humira used for in dogs?

Humira is not used in dogs.

Humira is a brand-name, premium-priced prescription drug prescribed to treat rheumatoid arthritis, juvenile idiopathic arthritis (JIA), spinal arthritis (ankylosing spondylitis), inflammatory bowel disease (Crohn’s disease and ulcerative colitis), plaque psoriasis, psoriatic arthritis, uveitis, and hidradenitis suppurativa. All of these conditions involve the immune system attacking healthy tissues, causing inflammation, pain, and eventually permanent injury to the tissues.

Dogs can get all of these conditions. Some, like rheumatoid arthritis and IBD, are common veterinary diagnoses. Psoriasis is relatively rare in dogs. Canine hidradenitis suppurativa—an inflammatory immune response to bacterial infection of the sweat glands—is extremely rare. 

For all these conditions, treatments usually consist of anti-inflammatory drugs, corticosteroids, or immune suppressants in more severe cases. Veterinarians do not use drugs like Humira. The active ingredient in Humira is adalimumab, a humanized monoclonal antibody. These drugs can’t be used in animals. 

Most drugs are small molecules. The body’s immune system usually doesn’t notice these drugs. Antibodies are big molecules. They catch the attention of the body’s immune system, and the immune system is designed specifically to identify and attack these big molecules. If you put antibodies from humans into an animal, the animal’s immune system will eventually destroy them. The drug will fail. To work, monoclonal antibodies (called mAbs) have to be species-specific.

Monoclonal antibodies for people are humanized. The only job of a monoclonal antibody is to “stick” to one specific section (called the epitope) of another molecule (called an antigen). The tiny part of the monoclonal antibody that does the sticking (called the binding part) is often not humanized. Scientists genetically engineer the rest of the molecule to look like something a human body would make. To work in dogs, monoclonal antibodies must be caninized, that is, genetically engineered so that almost all of the molecule looks like it comes from dogs. 

Also, the working part of adalimumab may not work in dogs. Adalimumab suppresses the immune system by blocking tumor necrosis factor alpha (TNF-α), a protein that controls and activates the inflammatory response. Humira renders this protein ineffective, preventing the immune system from attacking healthy tissues. Dogs have a similar molecule called canine TNF-α, but its structure is not as complex as the human version, so adalimumab may not work. 

Veterinary researchers are working with the adalimumab molecule to produce a dog version of Humira. They have arrived at a working biosimilar version they’re calling Humivet-1. The results are promising, but the work isn’t finished yet. 

Is Humira safe for dogs?

Veterinarians do not know if Humira is safe for dogs. 

If and when a canine version of Humira is developed, it could cause serious problems in the dog the way Humira does in people. The FDA has mandated a black box warning about the risks of serious infections and cancer in people taking Humira. 

Adalimumab is a TNF blocker that powerfully suppresses the immune system, increasing the risk of serious infections. TNF blockers can worsen existing infections of tuberculosis and hepatitis B in people, but dogs do not get infected with hepatitis B. TNF inhibitors also make people more vulnerable to certain types of cancers, including lymphoma, leukemia, and non-melanoma skin cancers. All of these could be a risk when a dog version of adalimumab is developed.

Adalimumab also increases the risk of nervous system problems, aplastic anemia, and worsening of heart failure. All of these may be risky when a canine version of Humira becomes available.

Side effects of Humira in dogs

Humira is not used in dogs, so dogs have no recorded Humira side effects. Veterinary researchers are using the active ingredient in Humira to engineer a dog version of the drug. We do not know how that drug will affect dogs, but the most common side effects of Humira in people are:

• Injection site reactions
• Infections
• Skin rash
• Headache
• Sinus swelling (sinusitis)

Humira’s most serious side effects in people are:

• Serious infections
• Malignancies
• Severe nervous system disorders or worsening of existing nervous system disorders
• Blood disorders include low white blood cells (leukopenia), low platelet counts (thrombocytopenia), and aplastic anemia.
• Heart failure
• Heart problems, including heart attack
• Liver problems, including liver failure
• Lung problems
• Gastrointestinal bleeding
• Severe allergic reactions

Interactions of Humira with other pet meds

Humira has not been studied or used in dogs, so veterinarians do not know if it has drug interactions with other pet medications.

We do know that TNF blockers should not be used with live vaccines. Because TNF blockers like Humira weaken the immune system, live vaccines that are normally safe could bring about serious infections. Live vaccines given to dogs include the parvovirus vaccine, adenovirus-2 vaccine, and some forms of distemper and parainfluenza vaccines.

TNF blockers may make other vaccines less effective.

Humira alternatives for dogs

Among the conditions Humira treats in people, dogs commonly experience rheumatoid arthritis, inflammatory bowel disease, and uveitis (inflammation of eye tissues). Psoriasis is rare in dogs, and hidradenitis suppurativa has only a handful of reported cases. Since Humira is not used in dogs, pets will be treated with the therapies most commonly used in people.

For rheumatoid arthritis and other types of immune-mediated arthritis, such as osteoarthritis, veterinarians use corticosteroids. If that doesn’t work, they add immune suppressants such as azathioprine, cyclosporine, or cyclophosphamide.

Inflammatory bowel disease is an intestinal autoimmune disease. Veterinarians treat inflammatory bowel disease in dogs with dietary changes, antibiotics such as metronidazole or tylosin, and corticosteroids such as prednisolone, prednisone, or budesonide. If corticosteroids aren’t effective, a veterinarian may add an immunosuppressant such as azathioprine, sulfasalazine, cyclosporine, or chlorambucil.

Healthcare professionals also use Humira to treat noninfectious immune-mediated uveitis, an inflammatory condition of the eye that causes red eye, eye irritation, narrow pupils, and swollen irises. In dogs, infections and injuries are the most common cause of uveitis, but they can experience uveitis caused by immune disorders, too. The treatment of choice is corticosteroid eye drops including dexamethasone or prednisolone acetate. Corticosteroid pills may be necessary if the back of the eye is affected. Other possible treatments include non-steroidal anti-inflammatory drugs (NSAIDs), such as Ocufen (flurbiprofen) or atropine eye drops.

Summary

Humira is not used in dogs because it will not work. Veterinarians are trying to develop a dog version of Humira, so that option may be available at some point. Do not give a dog Humira injections. Talk to the veterinarian if your dog’s current treatment for an autoimmune disorder is not working.