News|Articles|December 18, 2025

Virbac acquires feline hyperthyroidism drug Felanorm in €100 million deal

Virbac acquired an oral solution of methimazole, known as Felanorm in the US and Thyronorm outside the US. The drug is the first FDA-approved generic methimazole oral solution for hyperthyroidism in cats.

Virbac has acquired Felanorm (methimazole) Oral Solution from Norbrook Laboratories, the animal health pharmaceutical company said in a statement released yesterday. Felanorm is the only FDA-approved generic methimazole oral solution for treating hyperthyroidism in cats.

Virbac said it will begin selling the product immediately in the United States under the Felanorm name, with veterinary clinics having access to the medication through veterinary distributors across the nation.1,2

Outside the US, methimazole oral solution is sold under the brand name Thyronorm in the United Kingdom, Australia, and New Zealand. Virbac plans to continue selling the drug in these countries under the Thyronorm brand. According to Virbac, for now, Boehringer Ingelheim will continue to distribute the drug in Europe, with Elanco distributing it in Germany, until Virbac gradually takes over distribution.

Virbac and Norbrook were both founded around the same time, in 1968 and 1969, respectively. Following its founding, Norbrook, based in Northern Ireland, UK, went on to become a global top 20 manufacturer of animal health products.4 Virbac, also one of the world’s largest animal health companies, is present in more than 100 countries.5 Founded by a French veterinarian, Virbac’s global headquarters are located in Carros, France.

The transaction was priced at approximately 100 million euros.1 In the company statement, Paul Martingell, CEO of the Virbac Group, said Virbac is looking forward to working with Norbrook in the coming months to ensure a smooth integration and to support more senior cats with hyperthyroidism.1

“This acquisition aligns perfectly with our mission to provide veterinarians with high-quality, innovative solutions that improve animal health and well-being,” Karen Lass, DVM, senior veterinary marketing manager for Virbac US, said in a news release.2 “Felanorm's oral formulation offers an excellent option for cats requiring long-term hyperthyroidism treatment, and we're committed to ensuring veterinarians and pet owners have continued access to this important medication.”

Feline hyperthyroidism is an endocrine disorder causing an increase in thyroid hormones due to an enlarged thyroid gland in the neck of a cat. It is one of the most commonly diagnosed conditions in felines, with approximately 10% of cats over the age of 10 years being affected.2

Signs of the condition, if left untreated, include weight loss, increased appetite, increased heart rate and cardiac complications, hyperactivity and other behavioral changes, vomiting, diarrhea, and poor coat condition. With appropriate treatment, prognosis is generally good, although complications with other organs can negatively impact prognosis, according to the Cornell University College of Veterinary Medicine.3

Felanorm is available in 30 mL and 100 mL sizes with a 1 mL dosing syringe. The drug received FDA approval in the US in July 2024.6 According to the FDA, dose adjustments should be made in 2.5 mg increments, with a maximum daily dose of 20 mg, administered in divided doses and in no more than 10 mg at a single time.6 The medication is not intended for used in pregnant or lactating queens, or cats with renal, hepatic, or hematological disorders. Additionally, the medication contains anti-vitamin K activity and may induce bleeding diathesis without evidence of thrombocytopenia, Virbac noted.1

References

  1. Feline hyperthyroidism: Virbac acquires Felanorm. News release. Virbac. December 17, 2025. Accessed December 18, 2025. https://prnmedia.prnewswire.com/news-releases/feline-hyperthyroidism-virbac-acquires-felanorm-302645264.html
  2. Virbac acquires Felanorm® (methimazole) oral solution from Norbrook, strengthening feline health portfolio. Virbac. News release. Accessed December 18, 2025.
  3. Hyperthyroidism in cats. Cornell University College of Veterinary Medicine. Accessed December 18, 2025. https://www.vet.cornell.edu/departments-centers-and-institutes/cornell-feline-health-center/health-information/feline-health-topics/hyperthyroidism-cats
  4. Our history. Norbrook Laboratories. Accessed December 18, 2025. https://www.norbrook.com/us/about/our-history/
  5. Focusing on animal health, from the beginning. Virbac. Accessed December 18, 2025. https://us.virbac.com/home/discover-virbac/virbac-group.html
  6. FDA approves first generic methimazole for treating hyperthyroidism in cats. News release. US Food & Drug Administration. July 9, 2024. Accessed December 18, 2025. https://www.fda.gov/animal-veterinary/cvm-updates/fda-approves-first-generic-methimazole-treating-hyperthyroidism-cats

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