# Cyclosporine for Dogs: Side Effects and Owner Reviews Cyclosporine for dogs side effects are usually mild, with stomach upset topping the list of what owners report. Some dogs develop gum overgrowth, and a smaller number get infections because the drug quiets the immune system. Most dogs stay on it safely for months or years with monitoring. This article is educational and is not a substitute for veterinary diagnosis or treatment. ## Quick Answer - Vomiting, diarrhea, and appetite loss are the most common complaints owners report, and they often fade after the first week or two. - Giving the medicine with food, or chilling it in the fridge for an hour before dosing, can reduce stomach upset. - Gum overgrowth (gingival hyperplasia) shows up in some dogs on long-term therapy and may need dental care or a dose change. - About one third of dogs in a referral population developed at least one new infection while taking cyclosporine [1]. - Never stop or change the dose on your own. Call your veterinarian first. ## What Cyclosporine Is and What Veterinarians Use It For Cyclosporine is an immunosuppressant. It calms specific immune cells so the body stops attacking its own tissues or rejects a transplanted surface. Veterinarians prescribe it for immune-mediated conditions, inflammatory diseases, and some eye problems. Common uses include: - Keratoconjunctivitis sicca (KCS, or dry eye), where cyclosporine helps tear production and reduces surface inflammation [2][3] - Immune-mediated skin disease, such as atopic dermatitis and perianal fistulas - Inflammatory bowel disease and other chronic gut inflammation - Meningomyelitis of unknown origin, often alongside prednisolone [4] - Rare conditions like eosinophilic cystitis [5] and trapped neutrophil syndrome [6] A subconjunctival implant that releases cyclosporine slowly is also available for dogs with dry eye who do not respond well to daily drops [3]. Your veterinarian picks the form and route based on your dog's diagnosis. ## How Cyclosporine Works Cyclosporine blocks a protein called calcineurin inside T lymphocytes. T cells are the immune system's coordinators. When calcineurin is blocked, those cells produce less of the chemical signals that drive inflammation and tissue attack. The result is a quieter immune response. That helps in two ways. It reduces the damage caused by an overactive immune system, and it can reduce the inflammation that keeps certain glands from working properly, such as the tear glands in dry eye [2]. The trade-off is that a quieter immune system is less able to fight off bacteria, fungi, and parasites. That is why infection monitoring matters during treatment [1]. ## Dosing Basics: Who Decides, How to Give It, and Missed Doses Your veterinarian calculates the dose from your dog's weight, diagnosis, and overall health. There is no single dose that fits every dog. Never borrow a dose from another pet or adjust it yourself. Cyclosporine comes as capsules, liquid, and topical eye products. Most dogs take the oral form once or twice daily. Giving it with a small meal improves absorption and reduces nausea. If you miss a dose: - Give it when you remember, unless it is almost time for the next dose. - Skip the missed dose if the next one is close. Do not double up. - Call your veterinarian if you miss more than one dose in a row. Your veterinarian will likely check bloodwork before starting and periodically during treatment. Report any new medication, supplement, or change in your dog's condition at each visit. ## Cyclosporine for Dogs Side Effects: What Owners Report Owners describe a fairly consistent pattern. Stomach upset comes first, usually within the first days to weeks. Gum changes and infections tend to appear later, with longer treatment courses. ### Common Side Effects Vomiting is the side effect owners mention most. It is often mild and linked to giving the medicine on an empty stomach. Diarrhea, soft stool, and reduced appetite are also common early complaints. Many dogs adjust within one to two weeks. Gum overgrowth is another owner-reported issue. The gums thicken and can cover part of the teeth. It is not painful at first, but it can trap food and lead to dental disease over time. Your veterinarian may recommend a dental cleaning, a dose adjustment, or a switch to another drug. ### Serious Side Effects Infection is the most important serious risk. In one UK referral population, 33.2% of dogs (88 of 265) developed one or more new infections while receiving cyclosporine [1]. Bacterial infections were the most frequent group, affecting 26.0% of dogs (69 of 265) [1]. These were dogs seen at a referral hospital, so they may have been sicker than the average pet. Still, the number is worth knowing. Severe vomiting, bloody diarrhea, lethargy, fever, or a sudden lack of appetite warrant a call. These can signal infection, pancreatitis, or another serious problem. ### Side Effect Table | Side effect | How common or serious | What to do | |---|---|---| | Vomiting | Common, usually mild | Give with food. Call your vet if it lasts more than 24 hours or your dog cannot keep water down | | Diarrhea | Common, usually mild | Withhold treats, offer small bland meals. Call if bloody or lasting more than 2 days | | Appetite loss | Common, usually mild | Try feeding with the dose. Call if your dog skips more than 2 meals | | Gum overgrowth | Uncommon, develops over months | Mention at your next visit. May need dental care or a dose change | | New infection | About 1 in 3 dogs in one referral group [1] | Call your vet for fever, wounds that will not heal, or urinary signs | | Lethargy or weakness | Uncommon, can be serious | Call your vet the same day | If your dog is on other immune-suppressing drugs, the infection risk may be higher. Ask your veterinarian how to balance the benefits and risks for your dog's specific condition. ## Who Should Not Take Cyclosporine and What Interacts With It Cyclosporine is not right for every dog. Your veterinarian will review your dog's history before prescribing. Dogs who should not take it, or who need extra caution, include: - Dogs with active infections that are not yet controlled - Dogs with a history of certain cancers, since immune suppression can affect tumor surveillance - Dogs with significant liver or kidney disease - Dogs who have had an allergic reaction to cyclosporine or a similar drug - Pregnant or breeding dogs, unless your veterinarian specifically recommends it Drug interactions matter. Cyclosporine is processed by liver enzymes, so other drugs that use the same pathway can raise or lower its blood level. Common examples include ketoconazole, itraconazole, erythromycin, and some seizure medications. Tell your veterinarian about every drug, supplement, and topical product your dog receives, including over-the-counter items. If your dog also takes prednisolone, ask about the combined plan. One study found that dogs with suspected spinal meningomyelitis of unknown origin had fewer relapses when cyclosporine was added to prednisolone compared with prednisolone alone [4]. Your veterinarian will weigh that benefit against the added infection risk. Vaccines are another consideration. Live vaccines may be less effective or riskier in an immune-suppressed dog. Ask your veterinarian before any vaccination while your dog is on cyclosporine. ## Overdose and When to Call a Veterinarian or Poison Control An overdose can cause severe vomiting, diarrhea, lethargy, and loss of appetite. If you think your dog ate extra doses, call your veterinarian right away. If your regular clinic is closed, call the ASPCA Animal Poison Control Center at (888) 426-4435 or the Pet Poison Helpline at (855) 764-7661. Both may charge a consultation fee. Bring the bottle with you or have the label ready. The number of milligrams per capsule or milliliter of liquid helps the veterinarian decide on treatment. Do not wait for symptoms to appear before calling. ## Limitations and When to Contact a Veterinarian This article covers general patterns, but your dog's situation is individual. Only your veterinarian can examine your dog, review the history, and decide what is safe. Use the guidance below as a starting point, not a substitute for professional advice. Call your veterinarian the same day if your dog: - Vomits more than twice in a day or cannot keep water down - Has bloody diarrhea or black, tarry stool - Refuses food for more than 24 hours - Seems weak, wobbly, or unusually quiet - Has a fever, a wound that will not heal, or straining to urinate - Develops new swelling, redness, or discharge around the eyes or gums Go to an emergency clinic now if your dog: - Collapses or has a seizure - Has trouble breathing - Has severe abdominal pain or a swollen, hard belly - Cannot stand or seems disoriented Schedule a routine visit if you notice: - Gums that look thicker or are growing over the teeth - Gradual weight loss or a dull coat - New itching, hair loss, or skin odor - Any change that worries you, even if it seems small Your veterinarian may adjust the dose, add a medication to protect the stomach, or switch to a different treatment. Do not make those changes on your own. ## Frequently Asked Questions ### Does cyclosporine make dogs vomit? Yes, vomiting is one of the most common side effects owners report. It is often mild and linked to giving the medicine on an empty stomach. Giving the dose with a small meal usually helps. Call your veterinarian if vomiting lasts more than a day or your dog cannot keep water down. ### How long do cyclosporine side effects last in dogs? Most mild stomach upset fades within one to two weeks as your dog adjusts. Gum overgrowth and infection risk build over months of treatment. If side effects persist or worsen, your veterinarian may lower the dose or change the plan. ### Can cyclosporine cause long-term problems in dogs? The main long-term concerns are gum overgrowth and a higher risk of infection. In one referral group, about one third of dogs developed a new infection during treatment [1]. Regular checkups, bloodwork, and dental care help catch problems early. Many dogs stay on the drug for years with good monitoring. ### What should I do if my dog misses a cyclosporine dose? Give the missed dose when you remember, unless the next dose is close. If it is almost time for the next one, skip the missed dose and continue on schedule. Never give two doses at once. Call your veterinarian if you miss several doses in a row. ### Is cyclosporine safe to give with prednisone? Many dogs take both drugs together, and veterinarians often prescribe them as a pair for immune-mediated disease [4]. The combination can be more effective than either drug alone for some conditions, but it also raises infection risk. Your veterinarian will set the doses and monitor your dog closely. ### Can I stop cyclosporine suddenly if my dog seems better? No. Stopping suddenly can cause a flare of the underlying disease. Your veterinarian will usually taper the dose slowly over weeks or months. One case report described a dog who improved on cyclosporine and then had the drug tapered gradually after six months of treatment [5]. Always follow your veterinarian's tapering plan. ### Does cyclosporine help dogs with dry eye? Yes, cyclosporine is a standard treatment for keratoconjunctivitis sicca in dogs. It reduces inflammation on the eye surface and can help tear production [2]. A slow-release implant placed under the conjunctiva is another option for dogs who struggle with daily drops [3]. Your veterinary ophthalmologist can advise on the best form for your dog. If your dog takes other medications, it helps to know what side effects to expect. Our guide to [prednisone side effects in dogs](/knowledge/veterinary-medicine/pet-medication-guide/prednisone-side-effects-dogs) covers a drug often paired with cyclosporine. If your dog is also on antibiotics for an infection, see [antibiotic side effects in dogs](/knowledge/veterinary-medicine/pet-medication-guide/dog-antibiotics-side-effects). And if your dog is on thyroid medication, our article on [thyroid medication side effects](/knowledge/veterinary-medicine/pet-medication-guide/dog-thyroid-medication-side-effects) explains what to watch for. ## Related Articles - [What Are the Side Effects of Antibiotics in Dogs?](/knowledge/veterinary-medicine/pet-medication-guide/dog-antibiotics-side-effects) - [What Are the Side Effects of Clavamox for Dogs?](/knowledge/veterinary-medicine/pet-medication-guide/clavamox-side-effects-dogs) - [What Are the Side Effects of Prednisone in Dogs?](/knowledge/veterinary-medicine/pet-medication-guide/prednisone-side-effects-dogs) - [What Are the Side Effects of Thyroid Medication for Dogs?](/knowledge/veterinary-medicine/pet-medication-guide/dog-thyroid-medication-side-effects) - [Dog Anxiety Medication Side Effects: What to Watch For](/knowledge/veterinary-medicine/anxiety-and-behavior-support/dog-anxiety-medication-side-effects) - [What Are the Side Effects of Gabapentin for Dogs?](/knowledge/veterinary-medicine/pet-medication-guide/gabapentin-side-effects-dogs) - [Cyclosporine Eye Drops for Dogs: Uses and Safety](/knowledge/veterinary-medicine/pet-medication-guide/cyclosporine-eye-drops-dogs) - [Oclacitinib for Dogs: Side Effects and Owner Reviews](/knowledge/veterinary-medicine/pet-medication-guide/oclacitinib-dogs-side-effects-reviews) - [Cyclosporine for Dogs with Perianal Fistulas](/knowledge/veterinary-medicine/pet-medication-guide/cyclosporine-dogs-perianal-fistulas) ## References 1. [Occurrence of infections in dogs receiving ciclosporin in a single-centre UK referral population](https://pubmed.ncbi.nlm.nih.gov/42642047/). The Journal of small animal practice, 2026. 2. [A liposomal formulation of cyclosporine a shows promising results in treating symptoms of moderate to severe dry eye disease in dogs](https://pubmed.ncbi.nlm.nih.gov/41615622/). Drug delivery and translational research, 2026. 3. [A Sustained-Release Thermoplastic Polyurethane/Poly L-Lactide-Co-DL-Lactide (TPU/PLDLA) Cyclosporine-A Implant for the Treatment of Canine Keratoconjunctivitis Sicca: A Retrospective Case Series](https://pubmed.ncbi.nlm.nih.gov/42192580/). Veterinary ophthalmology, 2026. 4. [Cyclosporine and prednisolone treatment leads to fewer relapses compared with prednisolone alone in dogs with suspected meningomyelitis of unknown origin](https://pubmed.ncbi.nlm.nih.gov/40865564/). Journal of the American Veterinary Medical Association, 2025. 5. [Cyclosporine as a Novel Therapeutic Option for Eosinophilic Cystitis in a Paraplegic Dog](https://pubmed.ncbi.nlm.nih.gov/42444988/). Case reports in veterinary medicine, 2026. 6. [Successful therapy of a dog with trapped neutrophil syndrome using a combination of cyclosporine and prednisolone: a case report](https://pubmed.ncbi.nlm.nih.gov/41485978/). The Journal of veterinary medical science, 2026. ## Further Reading - [American Veterinary Medical Association: First Aid Tips for Pet Owners](https://www.avma.org/resources-tools/pet-owners/emergencycare/first-aid-tips-pet-owners) - [Merck Veterinary Manual: Dog Owners](https://www.merckvetmanual.com/dog-owners) - [Cornell Richard P. Riney Canine Health Center: Canine Health Information](https://www.vet.cornell.edu/departments-centers-and-institutes/riney-canine-health-center/canine-health-information)