Tyraxin

To the medical and pharmaceutical professions

Composition:
Each tablet contains:
Levo-thyroxine sodium                   0.1 mg = 100 mcg

Pharmacological properties:
The major thyroid hormones are L-thyroxine (T4) and L-triiodothyronine (T3). The amounts of T4 & T3 released into the circulation from the normally functioning thyroid gland are regulated by the amount of thyrotropin (TSH) secreted from the anterior pituitary gland. The principle effect of exogenous thyroid hormone is to increase the metabolic rate of body tissues.
The thyroid hormones are also concerned with growth and differentiation of tissues.
A large part of T3 is derived from T4 by deiodination in the peripheral tissues.

Pharmacokinetics:
-    Fasting increases absorption of the hormones. More than 99% of the circulating hormones are bound to serum proteins.
-    The half life of T4 in normal plasma is 6-7 days.

Indications:
Tyraxin tablets are indicated as replacement therapy for diminished or absent thyroid function, e.g. cretinism, myxedema, or hypothyroidism generally. It may also be used to suppress the secretion of TSH and in chronic lymphocytic thyroiditis. Thyroid hormone drugs are indicated as  diagnostic agents in suppression tests to differentiate suspected mild hyperthyroidism or thyroid gland autonomy.

Contraindications:-
Tyraxin tablets administration is contraindicated in untreated thyrotoxicosis, in acute myocardial infarction, hypersensitivity to the thyroid hormone and in the presence of uncorrected adrenal insufficiency because it increases the tissue demands for adrenocortical hormones and may cause an acute adrenal crisis in such patients.

Warnings:-
The use of thyroid hormones in the therapy of obesity, alone or combined with other drugs, is unjustified and has been shown to be ineffective neither is their use justified for the treatment of male or female infertility unless this condition is accompanied by hypothyroidism.

Precautions:
The therapy of myxedema coma requires simultaneous administration of glucocorticoids.
Tyraxin tablets should be used with caution in patients with cardiovascular disease including hypertension. Thyroid hormone therapy in patients with concomitant diabetes mellitus or diabetes insipidus or adrenal cortical insufficiency aggrevates the intensity of their symptoms.
In infants, excessive doses of thyroid hormone preparations may produce craniosynostosis.

Pregnancy:
Thyroid hormones do not readily cross the placental barrier. Thyroid replacement therapy to hypothyroid women should not be discontinued during pregnancy.

Lactation:
Caution should be exercised when thyroid hormone is administered to a nursing woman.

Drug interactions:
1-    In patients with diabetes mellitus thyroid therapy may cause an increase in the required dose of insulin or hypoglycemic agents.
2-    Thyroid replacement may potentiate anticoagulant effects with agents as warfarin or bis hydroxy coumarin.
3-    Thyroxine may be decreased when estrogens are started thus increasing thyroid requirements.
4-    Careful observation is required if catecholamines (e.g. epinephrine) are administered to patients receiving thyroid preparations as those preparations may enhance the episode of coronary insufficiency that may precipitate if patients with coronary artery disease injected with epinephrine.
5-    Cholestyramine or colestipol impairs absorption of T3 and T4 as they bind to the hormones so 4–5 hours should elapse between administration of them.

Side Effects:
Side effects are rare.

Overdosage:
The most common symptoms:
Nervousness, diarrhea, abdominal cramps, sweating tachycardia, cardiac arrythmias, angina pectoris, tremors.
Menstrual changes, increase in blood pressure, increase in appetite, weight loss, palpitation, insomnia, headache and intolerance to heat and fever.
Treatment:
1-    Dosage should be reduced or therapy temporarily discontinued and then reinstituted at a lower dose.
2-    Vomiting may be induced initially.
3-    Treatment is symptomatic and supportive.
4-    Administration of cholestyramine to interfere with thyroxine absorption and glucocorticoids to inhibit conversion of T4 to T3.


Dosage and Administration:
The usual starting dose is 50 mcg with increases of 50 mcg at 2 to 4 week intervals until the patient is euthyroid.
Adults:
- The usual maintainance dose for adults: 100 –200 mcg daily (One to two tablets daily)
- In adult Myxedema or hypothyroid patients with angina, the starting dose should be 25 mcg with increases at 2 to 4 week intervals of 25 to 50 mcg as determined by clinical response.
Pediatric:
Recommended dosage for congenital hypothyroidism.

Age Dose per day
Less than 6 months
     6-12 months
     1-5 yrs
     6-12 yrs
 
 ¼ – ½ tablet (25-50 mcg)
 ½ – ¾ tablet (50-75 mcg)
 ¾ – one tablet (75-100 mcg)
 1 – 1 ½ tablet (100-150 mcg)

Therapeutic category:
Thyroid hormone.
Legal category:
Prescription only medicine (POM).

Storage:
Store in a dry place at a temperature below 30° C.

Package:-
Boxes each contain 100, 50, 10 tablets

 

THIS IS A MEDICAMENT
Medicament is a product, which affects your health and its consumption contrary to instructions is dangerous for you. Follow strictly the doctor’s prescription, the method of use and the instructions of the pharmacist who sold the medicament.
- The doctor and the pharmacist are the experts in medicines, their benefits and risks.
- Do not by yourself interrupt the period of treatment prescribed.
- Do not repeat the same prescription without consulting your doctor.
- Keep all medicaments out of reach of children.

Council of Arab Health Ministers, Union of Arab Pharmacists.