Introduction

Company name: CEVA Animal Health Ltd

Address: 90 The Broadway

Chesham

Buckinghamshire

HP5 1EG

Telephone: 01494 781510

Fax: 01494 781519

Email: cevauk@ceva.com

Website: www.ceva.uk.com

Presentation

Cross-scored tablet divisible into sections by means of a groove to facilitate accurate dosage. For oral administration to dogs. Each tablet contains 200 μg of levothyroxine sodium.

Uses

Treatment of hypothyroidism in dogs. Levothyroxine sodium is a synthetic product chemically identical to the naturally occurring hormone “T4”. It is used to replace a deficient endogenous hormone, for the long term treatment of hypothyroidism in dogs.

Thyroid supplementation increases basal cellular metabolism and oxygen consumption thereby affecting the function of virtually all organ systems.

Dosage and administration

The recommended starting dosage of levothyroxine sodium is 10 μg/kg bodyweight orally every 12 hours. Because of variability in absorption and metabolism, the dosage may require alterations before a complete clinical response is observed. The initial dosage and frequency of administration are merely a starting point. Therapy has to be highly individualised and tailored to the requirements of the individual dog.

To adequately monitor therapy, trough values (just prior to treatment) and peak values (approximately three hours after dosing) of plasma T4 can be measured. In adequately dosed dogs peak plasma concentrations of T4 should be in the high-normal range (approximately 30-47 ηmol/l) and trough values should be above 19 ηmol/l. If T4 levels are outside this range the levothyroxine sodium dose can be adjusted in 50 – 200 μg increments, until the patient is clinically euthyroid and serum T4 is within the reference range. Plasma T4 levels can be retested two weeks after a dosage change, but clinical improvement is equally an important factor in determining individual dosage and this will take four to eight weeks. When the optimum replacement dose has been attained, clinical and biochemical monitoring may be performed every 6-12 months.

Contra-indications, warnings, etc

Do not use in dogs suffering from thyrotoxicosis or uncorrected adrenal insufficiency. Administer with caution to animals with clinically significant heart disease, or other complications for which a sharply increased metabolic rate might prove hazardous.

Restoration of physical activity may unmask or intensify other problems, such as arthritis.

Adverse effects of thyroid hormones are generally associated with excessive dosage and correspond to the symptoms of hyperthyroidism.

A sudden increase in demand for oxygen delivery to peripheral tissues, plus the chronotropic effects of T4, may place undue stress on a poorly functioning heart, causing decompensation and signs of congestive heart failure. Hypothyroid dogs suffering from hypoadrenocorticism have a decreased ability to metabolise T4 and therefore an increased risk of thyrotoxicosis. For these dogs, gradual introduction of levothryroxine therapy starting with 25% normal dose, increasing by 25% increments every fortnight until optimal stabilisation is achieved.

Adjustments in the dosage of digitalis may be necessary in a patient that had previously compensated congestive heart failure and that is placed on thyroid hormone supplementation. Prednisone increases T4 binding to serum carrier proteins. This may result in lower T4 transfer rates from serum to extravascular sites and increased extravascular T4 binding. Insulin requirements are decreased in the hypothyroid patient with diabetes.

Overdoses of three to six times label recommended starting dose for four consecutive weeks resulted in no significant clinical signs that could be attributed to treatment. However, following chronic over supplementation, overdose will eventually lead to thyrotoxicosis, manifested by: weight loss without anorexia, polydispia, polyuria, panting and probably tachycardia, and nervousness. The presence of these signs should result in evaluation of T4 serum concentration to confirm the diagnosis, and immediate discontinuation of the supplement.

Forthyron® may be used during pregnancy or lactation according to a risk:benefit assessment. The dosage may have to be increased if symptoms of hypothyroidism return.

For animal treatment only. Keep out of reach and sight of children.

Pharmaceutical precautions

Wash hands after administering the tablets.

Do not store above 25°C.

Tablet portions can be kept for 4 days in the blister pack.

Any unused product or waste material should be disposed of in accordance with national requirements.

Legal category

POM-V

Packaging Quantities

Blisters, consisting of aluminium foil, and a white opaque PVC/PE/PVDC foil.

Box of 25 blisters of 10 tablets.

Further information

Nil.

Marketing authorisation number

Vm 16849/4005.