Felimazole for Cats

Introduction

Company name: Dechra Veterinary Products Limited
Address: (A business unit of Dechra Pharmaceuticals PLC)
Sansaw Business Park
Hadnall, Shrewsbury
Shropshire SY4 4AS
Telephone: 01939 211200
Fax: 01939 211201
Email: info@dechra-uk.com
Website: www.dechra.com

Presentation

Pink sugar-coated biconvex tablets, 5.5 mm diameter. Each tablet contains:
Active substance: 2.5 mg Thiamazole (Methimazole)
Excipients: Titanium dioxide (E171) 1.12 mg
Erythrosine (E127) 0.01 mg

Uses

Thiamazole is indicated for both the stabilisation of feline hyperthyroidism prior to surgical thyroidectomy and for the long-term treatment of feline hyperthyroidism.

Dosage and administration

For oral administration only.
For the stabilisation of feline hyperthyroidism prior to surgical removal of the thyroid gland, one 2.5 mg tablet morning and evening. This should ensure euthyroidism within 3 weeks in most cases.
For long-term treatment of hyperthyroidism, the starting dose should be 2.5 mg twice daily. After 3 weeks, the dose should be titrated to effect according to the serum total T4. Dose adjustments should be made by increments of 2.5 mg. Wherever possible, the total daily dose should be divided into two and administered morning and evening. Tablets should not be split. The aim should be to achieve the lowest possible dose rate.
If, for reasons of compliance, once a day dosing with a 5 mg tablet is preferable, then this is acceptable although reduced efficacy can be expected compared to a twice daily regime. The 5 mg tablet is also suitable for cats requiring higher dose rates.
The dose administered must not exceed 20 mg/day.
For long-term treatment of hyperthyroidism the animal should be treated for life.
Advice on correct administration: Haematology, biochemistry and serum total T4 should be assessed before initiating treatment and after 3 weeks, 6 weeks, 10 weeks, 20 weeks and thereafter every 3 months and the dose titrated as necessary. If more than 10 mg per day is required animals should be monitored particularly carefully.

Contraindications, warnings, etc

Do not use in cats suffering from systemic disease such as primary liver disease or diabetes mellitus.
Do not use in cats showing signs of autoimmune disease.
Do not use in animals with disorders of white blood cells, such as neutropenia and lymphopenia.
Do not use in animals with platelet disorders and coagulopathies (particularly thrombocytopenia).
Do not use in pregnant or lactating females.
Do not use in cats with hypersensitivity to thiamazole or the excipient, polyethylene glycol.
Adverse reactions: Adverse reactions have been reported following long term control of hyperthyoidism. In many cases symptoms may be mild and transitory and not a reason for withdrawal of treatment. The more serious effects are mainly reversible when medication is stopped.
Adverse reactions are uncommon. The most common clinical side effects that are reported include vomiting, inappetance/anorexia, lethargy, severe pruritus and excoriations of the head and neck, bleeding diathesis and icterus associated with hepatopathy, and haematological abnormalities (eosinophilia, lymphocytosis, neutropenia, lymphopenia, slight leucopenia, agranulocytosis, thrombocytopenia or haemolytic anaemia). These side effects resolve within 7-45 days after cessation of thiamazole therapy.
Possible immunological side effects include anaemia, with rare side effects including thrombocytopenia and serum anti-nuclear antibodies, and, very rarely, lymphadenopathy. Treatment should be stopped immediately and alternative therapy considered following a suitable period for recovery.
Following long-term treatment with thiamazole in rodents, an increased risk of neoplasia in the thyroid gland has been shown to occur, but no evidence is available in cats.
If you notice any serious effects or other effects not mentioned in the data sheet, please inform your veterinary surgeon.
Special precautions for use in animals: As thiamazole can cause haemoconcentration, cats should always have access to drinking water.
If more than 10 mg per day is required animals should be monitored particularly carefully.
Use of the product in cats with renal dysfunction should be subject to careful risk:benefit assessment by the clinician. Due to the effect thiamazole can have on reducing the glomerular filtration rate, the effect of therapy on renal function should be monitored closely as deterioration of an underlying condition may occur.
Haematology must be monitored due to risk of leucopenia or haemolytic anaemia.
Any animal that suddenly appears unwell during therapy, particularly if they are febrile, should have a blood sample taken for routine haematology and biochemistry.
Neutropenic animals (neutrophil counts <2.5x109/l) should be treated with prophylactic bactericidal antibacterial drugs and supportive therapy.
Please refer to 'Dosage and administration' for monitoring instructions.
Use during pregnancy, lactation or lay: Laboratory studies in rats and mice have shown evidence of teratogenic and embryotoxic effects of thiamazole. The safety of the product was not assessed in pregnant or lactating cats. Do not use in pregnant or lactating females.
Interaction with other medicinal products and other forms of interaction: If your cat is being treated with any other medications advise your veterinary surgeon prior to the use of Felimazole®.
Concurrent treatment with phenobarbital may reduce the clinical efficacy of thiamazole.
Thiamazole is known to reduce the hepatic oxidation of benzimidazole wormers and may lead to increases in their plasma concentrations when given concurrently.
Thiamazole is immunomodulatory therefore this should be taken into account when considering vaccination programmes.
Special precautions to be taken by the person administering the veterinary medicinal product to animals: Wash hands after use.
In the case of accidental ingestion, seek medical advice immediately and show the data sheet to the physician.
Thiamazole may cause vomiting, epigastric distress, headache, fever, arthralgia, pruritus and pancytopenia. Treatment is symptomatic.
Wash hands with soap and water after handling litter used by treated animals.
Do not eat, drink or smoke while handling the tablet or used litter.
Do not handle this product if you are allergic to antithyroid products. If allergic symptoms develop, such as skin rash, swelling of the face, lips or eyes or difficulty in breathing, you should seek medical attention immediately and show the package leaflet or label to the doctor.
Do not break or crush tablets.
As thiamazole is a suspected human teratogen, women of child-bearing age should wear gloves when handling litter of treated cats.
Pregnant women should wear gloves when handling the product.
Overdose: In tolerance studies in young healthy cats, the following dose-related clinical signs occurred at doses of up to 30 mg/animal/day: anorexia, vomiting, lethargy, pruritus and haematological and biochemical abnormalities such as neutropenia, lymphopenia, reduced serum potassium and phosphorous levels, increased magnesium and creatinine levels and the occurrence of anti-nuclear antibodies. At a dose of 30 mg/day some cats showed signs of haemolytic anaemia and severe clinical deterioration. Some of these signs may also occur in hyperthyroid cats treated at doses of up to 20 mg per day.
Excessive doses in hyperthyroid cats may result in signs of hypothyroidism. This is however unlikely, as hypothyroidism is usually corrected by negative feedback mechanisms.
Please refer to the section Adverse reactions.
If overdosage occurs, stop treatment and immediately contact your veterinary surgeon. Give symptomatic and supportive care.
General precautions: For animal treatment only.
Keep out of the reach and sight of children.

Pharmaceutical precautions

Do not store above 25°C. Do not use after the expiry date which is stated on the label and carton after EXP. Keep the container tightly closed in order to protect from moisture. Keep the container in the outer carton. Keep out of the reach and sight of children.
Disposal: Dispose of used packaging in the household refuse. Unused product should be returned to the veterinary surgeon.

Legal category

POM-V

Packaging quantities

Nature and composition of immediate packaging: White polypropylene tub with white low density polyethylene tamper evident lid containing 100 tablets.

Further information

To be supplied only on veterinary prescription.
Veterinary medicinal product authorised for use in UK and IE.
Manufacturer for the batch release: Dales Pharmaceuticals, Snaygill Industrial Estate, Keighley Road, Skipton, North Yorkshire, BD23 2RW.

Marketing authorisation holder (if different from distributor)

Dechra Limited, Dechra House, Jamage Industrial Estate, Talke Pits, Stoke-on-Trent, Staffordshire, ST7 1XW.

Marketing authorisation number