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Thiafeline Film-coated Tablets for Cats


Thiafeline Film-coated Tablets for Cats

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  • 2.5mg (pack of 120)

    Estimated dispatch on Thursday

    Was £38.79 Now £31.99

    Web code: Q10798

  • 5mg (pack of 120)

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    Was £55.69 Now £45.99

    Web code: Q11215

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Thiafeline Film-coated Tablets for Cats.

Thiafeline 2.5, 5 mg Film-coated Tablets for Cats (AT, BE, CZ, DE, EE, EL, ES, FR, HU, IE, IS, IT, LT, LU, LV, PL, PT, RO, SE, SK, UK)
Thiafeline vet 2.5, 5 mg Film-coated Tablets for cats (FI)
Thiafeline Vet (DK, NO)


Each tablet contains:

Active substance:
Thiamazole    2.5  mg

Titanium dioxide (E171)  0.45  mg
Carmoisine (E122)  0.009 mg

Active substance:
Thiamazole    5  mg

Titanium dioxide (E171)  0.15  mg
Sunset Yellow FCF (E110)   0.09  mg
Quinoline Yellow WS (E104)  0.075 mg


Film-coated tablet.
Orange biconvex tablets 5.5 mm diameter.


Target species


Indications for use, specifying the target species

For the stabilisation of hyperthyroidism in cats prior to surgical thyroidectomy.
For the long-term treatment of feline hyperthyroidism.


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. Refer to section 4.7.
Do not use in cats with hypersensitivity to thiamazole or the excipient, polyethylene glycol.

Special warnings for each target species

As thiamazole can cause haemoconcentration, cats should always have access to drinking water.

Special precautions for use

Special precautions for use in animals
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 <2.5 x 109/l) should be treated with prophylactic bactericidal antibacterial drugs and supportive therapy.

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 package leaflet or the label to the physician.
Thiamazole may cause vomiting, epigastric distress, headache, fever, arthralgia, pruritus and pancytopaenia. 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 anti-thyroid products. If allergic symptoms develop, such as a 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 and pregnant women should wear gloves when handling litter of treated cats.
Pregnant women should wear gloves when handling this product.

Adverse reactions (frequency and seriousness)

Adverse reactions have been reported following long term control of hyperthyroidism. In many cases signs 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 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 resolved 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 can occur. 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.

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

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.

Amounts to be administered and administration route

For oral administration only.
For the stabilisation of feline hyperthyroidism prior to surgical thyroidectomy and for the long term treatment of feline hyperthyroidism, the recommended starting dose is 5 mg per day.
Wherever possible, the total daily dose should be divided into two and administered morning and evening. Tablets should not be split.
If, for reasons of compliance, once daily dosing with a 5 mg tablet is preferable, then this is acceptable although   the 2.5 mg tablet given twice daily may be more efficacious in the short term. The 5 mg tablet is also suitable for cats requiring higher dose rates. 
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. At each of the recommended monitoring intervals, the dose should be titrated to effect according to the total T4 and to clinical response to treatment. Dose adjustments should be made in increments of 2.5 mg and the aim should be to achieve the lowest possible dose rate.
If more than 10 mg per day is required animals should be monitored particularly carefully.
The dose administered should not exceed 20 mg/day.
For long term treatment of hyperthyroidism the animal should be treated for life.

Overdose (symptoms, emergency procedures, antidotes), if necessary

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 phosphorus 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 Section 4.6: Adverse reactions.
If overdosage occurs, stop treatment and give symptomatic and supportive care.

Withdrawal period(s)

Not applicable.


Pharmacotherapeutic group:antithyroid preparations, sulphur-containing imidazole derivates.
ATC Vet Code: QH03BB02.

Pharmacodynamic properties

Thiamazole acts by blocking the biosynthesis of thyroid hormone in vivo. The primary action is to inhibit binding of iodide to the enzyme thyroid peroxidase, thereby preventing the catalysed iodination of thyroglobulin and T3 and T4 synthesis.

Pharmacokinetic particulars

Following oral dosing in healthy cats, thiamazole is rapidly and completely absorbed with a bioavailability of >75 %. However, there is a considerable variation between animals.
Peak plasma levels occur approximately 0.5-1 hour after dosing (tmax = 0.69 h). Cmax is between 1.1 and 2.7 µg/ml (1.78 µg/ml) and half-life is 3.3 h.
From man and rats it is known that the drug can cross the placenta and concentrates in the foetal thyroid gland. There is also a high rate of transfer into breast milk.
The drug residence time in the thyroid gland is assumed to be longer than in the plasma.
Metabolism and elimination
The metabolism of thiamazole in cats has not been investigated, however, in rats thiamazole is rapidly metabolised in the thyroid gland. About 64 % of the administered dose being eliminated in the urine and only 7.8 % excreted in faeces. This is in contrast with man where the liver is important for the metabolic degradation of the compound.


List of excipients

Tablet core:
Lactose monohydrate
Sodium starch glycolate Type A
Silica, colloidal anhydrous
Magnesium stearate

Cellulose, microcrystalline
Lactose monohydrate
Titanium dioxide (E171)
Sunset Yellow FCF (E110)
Quinoline Yellow WS (E104)


Not applicable.

Shelf life

Shelf-life of the veterinary medicinal product as packaged for sale:  30 months.

Special precautions for storage

Keep the blister in the outer package in order to protect from light.

Nature and composition of immediate packaging
30 tablets in a cardboard carton containing 1 aluminium/pvcstrips each strip with 30 tablets.
60 tablets in a cardboard carton containing 2 aluminium/pvc strips each strip with 30 tablets.
120 tablets in a cardboard carton containing 4 aluminium/pvc strips each strip with 30 tablets.
150 tablets in a cardboard carton containing 5 aluminium/pvc strips each strip with 30 tablets.
300 tablets in a cardboard carton containing 10 aluminium/pvc strips each strip with 30 tablets.
Not all pack sizes may be marketed.

Data Sheets




Shipping charges mainland UK zone1

ValueWeightDelivery Charge
Over £49.00Any WeightFREE
Under £49.00No weight limit£4.50
Under £49.00Under 250g£2.99

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Prescription items will be sent on receipt of a valid signed and dated prescription.

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Please ring us on 01833 641112 for more information.

Refrigerated Items

Refrigerated items will be sent by carrier or Royal Mail with coolpacks unless you pay for a premium for a refrigerated delivery. We will contact you prior to despatch for your instructions.


We want you to be completely satisfied with any purchase. If not any item* can be returned to us within 14 days of receipt for exchange or refund Please give us a ring for a returns number on 01833 641112 or alternatively email [email protected] to obtain a returns number.

*Due to legal requirements medicines may not be returned except to correct an error in despatch or in response to an "official recall". If an item is believed to be faulty it should be returned for inspection and it may be necessary to forward it to the manufacturers for testing before replacements or refunds can be authorised. This does not infringe legal rights. Please contact our customer services for a "Returns Number" which must appear on the outside of the package or it will not be accepted. We advise customers to use an insured method of shipping and to retain proof of despatch. We may refuse returns on products specially obtained or manufactured to order. Items must be returned unsoiled and unused and sent adequately packed and carriage paid.

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