POM-V Prescription Required Companion Animal

Felimazole 5 mg/ml Oral Solution for Cats

Name: Felimazole 5 mg/ml Oral Solution for Cats
Brand: Dechra Regulatory B.V.

Active ingredient: Thiamazole

Form

Liquid

Species

Cats

Manufacturer

Dechra Regulatory B.V.

VMD MA No.

50406/3031

What it's used for

For the long-term treatment of feline hyperthyroidism.

Full indications, dosage and side effects ↓

View official SPC (PDF)

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£15.98

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Prescription required

Your vet must provide a written prescription on request. You can then purchase from any licensed online retailer.

Clinical information

Felimazole 5 mg/ml Oral Solution for Cats — SPC Details

Source: VMD Summary of Product Characteristics (SPC). Last updated 27 Mar 2026.

For the long-term treatment of feline hyperthyroidism.

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 (1 ml of the veterinary medicinal product).
Wherever possible, the total daily dose should be divided into two equal doses and
administered morning and evening.
If, for reasons of compliance, once daily dosing is preferable, then this is acceptable,
although the twice-daily dose may be more efficacious in the short term.
In order to administer the dose accurately, use the syringe provided in the
package. The syringe fits on the bottle and is graduated in 0.25 mg increments up to
5 mg. Withdraw the required dose and administer the veterinary medicinal product
directly into the cat’s mouth.
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 (0.5 ml of the veterinary
medicinal product) and the aim should be to achieve the lowest possible dose rate. In
cats that require particularly small dose adjustments, increments of 1.25 mg of
thiamazole (0.25 ml of the veterinary medicinal product) can be used.
If more than 10 mg per day is required (2 ml of the veterinary medicinal product)
animals should be monitored particularly carefully.
The dose administered should not exceed 20 mg/day (4 ml of the veterinary
medicinal product).
For long-term treatment of hyperthyroidism, the animal should be treated for life.

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 cases of hypersensitivity to the active substance or to any of the
excipients.
Please refer to section 3.7.

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 and, in these cases, treatment should be stopped immediately and
alternative therapy considered, following a suitable period for recovery.
Uncommon
(1 to 10 animals / 1,000
animals
treated):
Vomiting
, Anorexia
, Inappetence
, Lethargy
Pruritus
1,2
, Excoriation
1,2
Prolonged bleeding
1,3,4
Icterus
1,4
, Hepatopathy
Eosinophilia
, Lymphocytosis
, Neutropenia
,
Lymphopenia
, Leucopenia
(slight),
Agranulocytosis
Thrombocytopenia
1,5,6
, Haemolytic anaemia
Rare (1 to 10 animals /
10,000 animals treated):
Autoimmune disorder (serum anti-nuclear
antibodies)
Very rare
(<1 animal / 10,000 animals
treated, including isolated
reports):
Lymphadenopathy
, Anaemia
1
These side-effects resolve within 7-45 days after cessation of thiamazole therapy.
Severe and of the head and neck.
Sign of a bleeding diathesis.
Associated with hepatopathy.
Immunological side-effect.
Occurs uncommonly as a haematological abnormality and rarely as an
immunological side effect.
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.
Reporting adverse events is important. It allows continuous safety monitoring of a
veterinary medicinal product. Reports should be sent, preferably via a veterinarian, to
either the marketing authorisation holder, or its local representative, or the national
competent authority via the national reporting system. See the package leaflet for
respective contact details.

In order to enhance stabilisation of the hyperthyroid patient the same feeding and
dosing schedule should be used daily.

Special precautions for safe use in the target species:
•
animals should be monitored particularly carefully.
•
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.
•
•
febrile, should have a blood sample taken for routine haematology and
biochemistry.
•
/litre) should be treated with
prophylactic bactericidal antibacterial drugs and supportive therapy.
•
to drinking water.
•
Special precautions to be taken by the person administering the veterinary medicinal
product to animals:
•
milk, women of child-bearing age and lactating women must wear non-permeable
single use gloves when handling the veterinary medicinal product, vomit or used
litter of treated animals. If you are pregnant, think you may be pregnant or are
attempting to conceive, you should not administer the veterinary medicinal
product or handle the litter/vomit of treated cats.
•
contact. Do not handle this veterinary medicinal product if you are allergic to
thiamazole or one of the excipients. 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 insert or the label to the
physician.
•
and eye contact including hand-to-eye contact. In case of accidental skin and/or
eye contact, rinse exposed skin and/or eyes immediately with clean running
water. If irritation develops, seek medical advice immediately and show the
package insert or the label to the physician.
•
(joint pain), pruritus (itching) and pancytopaenia (decrease in blood cells and
platelets). Avoid oral exposure including hand-to-mouth contact, especially by
children.
•
•
•
treated animals.
•
or used litter of treated animals.
•
veterinary medicinal product remaining on the tip of the dosing syringe should be
wiped off with a tissue. The contaminated tissue should be immediately disposed
of. The used syringe should be stored with the veterinary medicinal product in the
original carton.
•
the package insert or the label to the physician.
•
Special precautions for the protection of the environment:
Not applicable.

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.

This veterinary medicinal product does not require any special storage conditions.

Not applicable.

This information is sourced from the official Summary of Product Characteristics (SPC) published by the Veterinary Medicines Directorate (VMD). It is provided for informational purposes only and does not replace professional veterinary advice. Always consult your vet before administering any medication.

Price comparison

Felimazole 5 mg/ml Oral Solution for Cats Prices by Online retailer

Felimazole 5 mg/ml Oral Solution for Cats is a prescription-only veterinary medicine (POM-V). Prices are listed for information, with every retailer shown on equal terms. To buy it online you need a written prescription from your vet, which the retailer will ask for at checkout. Under the CMA Order your vet must provide one on request, with the fee capped at £21 from 2027. Your prescription rights →

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