Presentation

10 mg tablet: Round pink tablet with little spots.  Each tablet contains 10 mg carbimazole as active ingredient.  Colouring agent: Red ferric oxide (E172): 0.25 mg.          

15 mg tablet: Round dark pink tablet with little spots.  Each tablet contains 15 mg carbimazole as active ingredient.  Colouring agent: Red ferric oxide (E172): 0.75 mg.

Uses

Treatment of hyperthyroidism and hyperthyroidism-associated clinical signs in cats.

Dosage and administration

For oral use only.

Vidalta tablets should be administered at the same time every day, in particular in relation to timing of feeding.  Vidalta may be given with food or on an empty stomach, as long as this is not varied from day to day.

Do not break or crush Vidalta tablets.

The aim of treatment is to maintain total thyroxine concentrations (TT4) in the lower end of the reference range. Accordingly, the following dose recommendations for dosing during adjustment and maintenance phases are suggested. However dosing adjustment should be primarily based upon the clinical assessment of the individual cat. Monitoring of TT4, full haematology and liver and kidney parameters is advised at each recommended follow up visit.

Adjustment phase

The starting dose is a single daily oral administration of one tablet of 15 mg carbimazole per cat. Consideration could be given to a starting dose of Vidalta 10 mg daily where the TT4 concentration is only mildly increased, e.g. between 50 nmol/L and 100 nmol/L.

With the recommended starting dose of one Vidalta 15 mg tablet once daily, total thyroxine concentration (TT4) may decrease to within the euthyroid range (TT4<50 nmol/L) shortly after treatment initiation. A dose adjustment may be required as early as 10 days of treatment.

Dose adjustment should also be performed 3, 5 and 8 weeks after initiation of treatment, depending on both clinical and hormonal responses to treatment.

Maintenance phase

Follow-up visits every 3 to 6 months are recommended. The dose should be adjusted individually based on clinical signs and total thyroxine concentration (TT4). It is advisable to check TT4 10-14 days after dose adjustment.

The therapeutic dose of Vidalta ranges between 10 mg (one 10 mg tablet) and 25 mg (one 10 mg tablet and one 15 mg tablet) once daily.

Some cats require doses of less than 10 mg carbimazole daily. In these cases, alternative treatment should be used.

Dose increases should not be made in increments of greater than 5 mg.

Doses above 20 mg have only been trialled in a small number of cats and should be used with caution.

Contra-indications, warnings, etc.

Do not use in cats with haematological disorders, such as neutropenia, lymphopenia or thrombocytopenia.

Do not use in pregnant or lactating queens.

Do not use in cats with hypersensitivity to carbimazole.

Doses above 20 mg have only been trialled in a small number of cats. Adverse reactions may occur at this dose, therefore careful monitoring is recommended and the dose should be adjusted according to the risk/benefit assessment for the individual case.

Most frequent common adverse reactions include vomiting, diarrhoea, reduced appetite, as well as dermatological signs (pruritus, moist dermatitis, erythema, alopecia). These clinical signs are usually mild, adequately controlled by symptomatic therapy and do not require treatment discontinuation. Weight loss, dehydration, dyspnoea, lethargy, aggressiveness, disorientation, ataxia or pyrexia have also been reported in rare cases.

Treatment of hyperthyroidism may result in a reduction in the glomerular filtration rate. This can lead to unmasking of pre-existent renal dysfunction. Renal function should therefore be monitored (BUN and creatinine) before and during treatment, preferably at each visit of the dose adjustment and maintenance phases. The dose should be adjusted according to the risk/benefit assessment for the individual case.

Treatment of hyperthyroidism with carbimazole may also induce an elevation of liver enzymes (AP and ALT) or a worsening of pre-existing hepatic disorders. Liver enzymes should therefore be monitored before and during treatment, preferably at each visit of the dose adjustment and maintenance phases. Severe cases may require temporary or permanent treatment discontinuation. Liver enzyme elevations are usually reversible following drug discontinuation, although symptomatic therapy (nutritional and fluid support) may be required.

Transient anaemia, increase or decrease in white blood cell count, neutrophilia, thrombocytopenia, eosinophilia and/or lymphopenia may also occur. Haematology parameters should therefore be monitored on a regular basis before and during treatment, preferably at each visit of the dose adjustment phase and maintenance phase. Treatment discontinuation is not required except in case of persistent and marked disorder. In most cases, the abnormalities will resolve spontaneously within 1 month after treatment discontinuation.

In case of overdosage, adverse effects that may appear include, but are not limited to, weight loss, inappetence, vomiting and lethargy. Coat and skin abnormalities (erythema, hair loss), as well as haematological/biochemical changes (eosinophilia, lymphocytosis, neutropenia, lymphopenia, slight leucopenia, agranulocytosis, thrombocytopenia or haemolytic anaemia) may also appear. In particular, at a daily dose of 45 mg carbimazole, haematological changes (decreased red blood cell count, haemoglobin concentration and haematocrit, and increased mean corpuscular volume) have been reported in healthy cats. Hepatitis and nephritis have also been reported.

Total thyroxine concentrations (TT4) below the lower limit of the reference range may be observed during treatment although this is rarely linked to overt clinical signs. Decreasing the dose will lead to an increase in TT4. Dose adjustment should not be made based on TT4 only.

A small proportion of cats with thyroid adenoma may fail to respond or have a poor response to treatment.

Thyroid carcinoma is a rare cause of hyperthyroidism in the cat and medical management alone is not recommended in such cases as it is not curative.

Operator warnings:

In the case of accidental ingestion, seek medical advice immediately and show the package leaflet or the label to the physician.

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 hyperthyroidism inhibitors.

As carbimazole is a suspected human teratogen, women of child-bearing age should wear gloves when handling litter and/or vomit of treated cats.

Withdrawal period:

Not applicable.

FOR ANIMAL TREATMENT ONLY.

KEEP OUT OF REACH AND SIGHT OF CHILDREN.

Pharmaceutical precautions

The tablets should be dispensed in their original packs.

Do not store above 25°C.

Protect from humidity and light.

Keep the plastic container tightly closed to protect from moisture.

Do not remove the desiccant.

Any unused veterinary medicinal product or waste materials derived from such veterinary medicinal product should be disposed of in accordance with local requirements.

Legal category

POM-V           To be supplied only on veterinary prescription. 

Package quantities

30 or 100 Vidalta 10 mg or 15 mg tablets in a white high-density polyethylene tub with a tamper-evident child-resistant screw cap and desiccant capsule.

Further information

Methimazole, the active metabolite of carbimazole, inhibits thyroid hormone production and therefore cessation of treatment with carbimazole will result in a rapid (within 48 hours) return to pre-treatment thyroid hormone levels. Chronic administration is therefore necessary unless surgical or radiation-induced thyroidectomy is performed.

Marketing Authorisation numbers

10 mg tablets: Vm 01708/4529

15 mg tablets: Vm 01708/4530.

Marketing Authorisation holder

Intervet UK Ltd.

W alton Manor

Walton

Milton Keynes

Bucks MK7 7AJ

Date of text preparation:

January 2008.