Below is the product datasheet. This has been provided by the manufacturer and should always be provided with the medication. Introduction 
Company name: MSD Animal Health
Address: Walton Manor
Walton
Milton Keynes
MK7 7AJ
Telephone: 01908 685685 (Customer Support Centre)
Fax: 01908 685555
Email: vet-support.uk@merck.com
Website: www.msd-animal-health.co.uk
Presentation
Clear, slight reddish coloured solution.
Each ml contains:
Active substance: Levothyroxine sodium (as multihydrate) 1 mg (equivalent to 0.97 mg levothyroxine).
Excipient: Ethanol 15% v/v.
Uses
Treatment of hypothyroidism in dogs.
Dosage and administration
For oral use only.
The dose of thyroid hormone replacement therapy with L-thyroxine must be tailored individually to each dog. A starting dose rate of 20 µg L-thyroxine sodium/kg (0.2 ml/10 kg bodyweight) once daily is recommended.
Four weeks later dose adjustment should be performed based on the clinical response to treatment and thyroid hormone concentration evaluated 4-6 hours after administration of the product. Further assessment and dose adjustment may be repeated at 4 week intervals if required.
A maintenance dose rate between 10 and 40 µg/kg body weight once daily is generally sufficient.
Dosing guide (see Table 1) – volume of product to be administered once daily (ml):
Table 1 - Dosing Guide for Leventa
|
| 
|
* The kilogram scale on the syringe provided is calibrated to the recommended starting dose of 20µg/kg.
Once a suitable dose rate and regime have been established, it is recommended to recheck clinical response and thyroid hormone concentrations every 6 months.
The improvement in clinical signs occurs differentially following the onset of treatment: metabolic signs improve within two weeks but dermatological signs may require 6 weeks or more of treatment before improvement is seen.
Leventa should be administered at the same time every day particularly in relation to timing of feeding. The absorption of L-thyroxine is influenced by food. Leventa may be given with food or on an empty stomach, as long as this is not varied from day to day. Preferentially L-thyroxine should be administered 2-3 hours prior to feeding to maximise absorption and minimize variation in absorption.
Instruction for use of the oral syringe: Gently push the syringe onto the insert in the bottle. Turn the bottle/syringe upside down and draw the solution into the syringe by pulling the plunger out. The edge of the ring on the end of the plunger should align with the expected volume or body weight in kilograms. Turn the bottle/syringe the right way up and remove the syringe from the insert. After administration, clean the syringe with clean water and allow to dry naturally.
See diagram.
Contra-indications, warnings, etc
Do not use in dogs with hyperthyroidism or uncorrected adrenal insufficiency (hypoadrenocorticism).
Do not use in case of hypersensitivity to levothyroxine sodium or to any of the excipients.
The product should be used with caution in dogs with cardiac disease, diabetes mellitus or treated adrenal insufficiency (hypoadrenocorticism). Levothyroxine therapy should be gradually introduced for these dogs. Start with 25% of the normal dose (5µg/kg once daily) and increase by 25% increments every two weeks until stabilised.
Adverse reactions associated with L-thyroxine sodium treatment are primarily those of hyperthyroidism, due to therapeutic overdose. They include weight loss, hyperactivity, tachycardia, polydipsia, polyuria, polyphagia, vomiting and diarrhoea. Transient, self-resolving skin reactions such as mild to moderate scale formation may occur.
Use in pregnancy
The safety of use in pregnant bitches, lactating bitches or animals intended for future breeding has not been evaluated. However, thyroxine is essential for normal foetal development. Hypothyroidism during pregnancy may be associated with impaired cognitive development and increased foetal mortality. During pregnancy, maternal thyroid hormone requirements may increase. Pregnant and lactating bitches receiving treatment should be monitored on a regular basis as dose requirements may change during pregnancy and lactation.
Use in lactating bitches or animals intended for future breeding has not been evaluated.
Drug interactions
L-thyroxine absorption may be impaired by the concurrent administration of antacids, e.g. aluminium or magnesium salts or calcium carbonate, or ferrous sulphate and sucralfate. Therefore, Leventa should not be administered within 2 hours of such products.
The therapeutic response to Leventa may be altered by compounds which influence thyroid hormone metabolism and disposition (e.g. drugs displacing protein-binding site, modifying serum thyroxine-binding globulin concentration, or altering hepatic degradation of thyroxine or peripheral conversion of thyroxine to tri-odothyronine). Thus, if Leventa is administered concurrently with a compound exhibiting such properties, thyroid hormone concentrations should be monitored and the dose of Leventa adjusted if needed.
Conversely, L-thyroxine supplementation may affect the pharmacokinetics and activity of concurrent therapies. In diabetic dogs treated with insulin, L-thyroxine supplementation may alter insulin requirements. In dogs with cardiac insufficiency, therapeutic response to cardiac glycosides may be decreased by L-thyroxine supplementation. Therefore, dogs receiving such products should be monitored carefully during initial treatment with Leventa.
Clinical signs of overdose with L-thyroxine are identical to those of hyperthyroidism and include body weight loss, hyperactivity, tachycardia, polydipsia, polyuria, polyphagia and diarrhoea. These signs are generally mild and fully reversible. Overdose may be accompanied by reversible changes in blood biochemistry, e.g. elevated glucose, inorganic phosphorus and albumin:globulin ratio, and reduced total protein and cholesterol.
User warnings
In the case of accidental ingestion, seek medical advice immediately and show the package leaflet or the label to the physician. Note: this product contains a high concentration of L-thyroxine sodium and may present a risk to humans if ingested.
Wash hands after use.
In case of eye contact, flush immediately with water.
Withdrawal periods
Not applicable.
For animal treatment only. Keep out of the reach and sight of children.
Pharmaceutical precautions
Store in a refrigerator (+2°C to +8°C). Store in the original container. Once opened use the product within 6 months.
Legal category
POM-V
Packaging Quantities
30 ml amber glass bottle with a transparent LDPE insert and with a white HDPE child-resistant cap with tamper-proof closure in a printed carton.
A 1 ml oral syringe graduated in 0.05 ml increments is supplied with the product.
Pack sizes: 1 x 30 ml, 6 x 30 ml and 12 x 30 ml. Not all pack sizes may be marketed.
Further information
In a tolerance study, healthy dogs treated with Leventa at 40 µg/kg body weight once daily for 91 consecutive days did not present any adverse clinical signs. At dose rates of 120 and 200 µg/kg body weight, dogs did not exhibit signs other than those of hyperthyroidism, mainly weight loss. These signs were mild and reversible, with recovery occurring within 5 weeks after cessation of treatment.
In the event of an overdose standard measures should be taken to remove non-absorbed drug from the gastro-intestinal tract.
Marketing authorisation number
Vm 01708/4527.
| 
