Thyrox | 50 mcg Tablet
Price: 0.00Generic: Levothyroxine Sodium
Manufactured By: Renata PLCVariant: Tablet 12.5 mcg, Tablet 75 mcg, Tablet 100 mcg, Tablet 25 mcg
PRESENTATION
Thyrox 25 mcg Tablet: Each tablet contains 25 mcg Levothyroxine Sodium BP.
Thyrox 50 mcg Tablet: Each tablet contains 50 mcg Levothyroxine Sodium BP.
Thyrox 75 mcg Tablet: Each tablet contains 75 mcg Levothyroxine Sodium BP.
Thyrox 100 mcg Tablet: Each tablet contains 100 mcg Levothyroxine Sodium BP.
INDICATION
Thyrox is indicated for the management of demonstrated thyroid hormone deficiency. Thyrox may be used to suppress Thyrotropin (Thyroid Stimulating Hormone, TSH) for the management of TSH- responsive tumors of the thyroid. Thyrox may be used in the management of thyroiditis such as Hashimoto's disease.
DOSAGE AND ADMINISTRATION
Thyrox therapy should be initiated at low dosage (e.g. 25 or 50 microgram/day) and increased at intervals of not less than two weeks, but not more than 50 microgram increments.
Adults: 100 to 150 microgram/day
Children: Congenital and acquired hypothyroidism
Note: The lowest dose compatible with clinical euthyroidism and satisfactory laboratory values should be used.
ADMINISTRATION
Thyrox can be taken as a single daily dose and is best ingested in the fasting state since food will impair absorption.
|
Age |
Dosage microgram/kg/day |
|
0-6 months |
Approximately 8 |
|
6-12 months |
Approximately 6 |
|
1-5 years |
Approximately 5 |
|
6-12 years |
Approximately 4 |
|
12 years and over |
Approximately 2 |
CONTRAINDICATIONS
Known hypersensitivity to L-thyroxine, which has been described rarely, is a contraindication to the use of Thyroxine
PRECAUTIONS AND WARNINGS
Initiation of therapy: In all cases, Thyrox should be initiated at not more than 50 microgram/day and gradually increased as described under DOSAGE AND ADMINISTRATION. Presence of cardiac disorder: Even smaller initial dosage (e.g. 12.5 to 25 microgram/day) should be used with increments of not more than 25 microgram/day at not less than two week intervals. If this routine is not tolerated because of angina, increments should be further reduced with prolongation of the intervals between changes. Use of a beta blocker may help to control angina.
Cortisone deficiency: Corticosteroid replacement therapy must precede initiation of T4 therapy to avoid Addisonian crisis in such conditions as hypopituitarism and adrenal insufficiency.
Monitoring: Because both clinically occult hyper-and hypothyroidism have been described in recipients of throxine replacement therapy, there are grounds for using radioimmunoassay monitoring of T4, T3, TSH and
response to Thyrotropin Releasing Hormone (TRH). Blood sampling times should be related to time of ingestion. Monitoring may assist management in malabsorption syndromes and the rare cases of tissue resistance. Monitoring may avoid development of side effects which resemble clinical thyrotoxicosis. Variability in clinical response Individual patients vary in response to both the maintenance dose of Thyrox and to the size and
frequency of dose increments. Too large an increment or too high a replacement dose can lead to manifestations of thyrotoxicosis which include:
Cardiovascular: Tachycardia, cardiac arrhythmias, palpitations, angina, myocardial ischemia, myocardial infarction, death;
Nervous system: Anxiety, restlessness, tremors, headache, poor concentration, emotional liability, sleep disturbance, mania, psychosis, psychotic depression, seizures, petit mat, status epilepticus, pseudotumor cerebri
(especially in children);
Gastrointestinal system: Diarrhoea, vomiting, malabsorption;
Skin: Warmth, erythema, telangiectasia, hyperhydrosis, alopecia, hyperpigmentation;
Respiratory system: Increased minute ventilation, tachypnoea;
Neuromuscular system: Myopathy, lid lag;
Reproductive system: Amenorrhoea, decreased libido, gynaecomastia ;
Metabolic: Fever, glucose intolerance, weight loss, premature craniosynostosis (in children), TRH suppression;
Renal disorder: There is no evidence that T4 dosage should be modified in the presence of renal failure.
However, thyroid function tests may be influenced and need careful interpretation action, vomiting, flatulence, euphoria, confusion, reduced libido, erectile dysfunction, irritability, vertigo, ataxia, tremor, dysarthria,
paraesthesia, fatigue, and oedema. Disturbances of attention, memory, coordination, and gait also occur frequently. Elevation of creatine kinase concentration and rhabdomyolysis have been reported rarely.
Liver disorders: In spite of the major involvement of the Liver in Thyrox metabolism, there is no evidence that dosage should be modified in the presence of cirrohosis, However, thyroid function tests may be influenced
by the cirrhosis itself and need careful interpretation.
Carcinogenicity: There is epidemiological evidence against the use of thyroid supplements enhancing the risk of breast cancer.
Pregnancy and lactation: There is no evidence that change of dosage is required during pregnancy provided adequate replacement was established before conception. Monitoring of TSH concentrations can give
guidance.
Thyroxine binding globulin (TBG) increases during permanency and therefore total T4 and T3 may appear to be elevated. Measurement of free T4 and T3 may be more appropriate. There is contradictory evidence concerning the passage of T4 and T3 across the placenta but it is unlikely that the fetus is at risk. There is contradictory evidence concerning the secretion of T4 and T3 in human breast milk.
However, T4 and T3 have been demonstrated in one case. The neonate should be carefully observed for evidence of altered thyroid function.
ADVERSE REACTION
Pseudotumor cerebri and premature craniosynostosis have been referred to under PRECAUTIONS AND WARNINGS as a possible complication of treatment of children. In both instances reduction of dosage and reappraisal of the maintenance needs are indicated. Slipped capital femoral epiphysis has also been described associated with high dosage. Allergy to both throxine and triiodothyronine has been described and overcome with use of 3.5 diiodo - 3" isopropyl thyronine (DIIP). Both reversible leucopenia and pancytopenia have been reported.
DRUG INTERACTIONS
Thyroxine can enhance the clinical effect of the following drugs, thus adjustment of dosage may be necessary:-coumarin anticoagulants, meperidine (pethidine), phenobarbitone, methadone, morphine, catecholamines, insulin, tricyclic antidepressants and dihydrotachysterol. Thyroxine can reduce the clinical effect of corticosteroids and digoxin, therefore adjustment of dosage may be necessary. The clinical effect of L-Thyroxine can be enhanced by ketamine. The clinical effect of Thyroxine can be reduced by cholestyramine, colestipol and soya flour, all of which interfere with its absorption from the gastro-intestinal tract and by propranolol and dexamethasone. Thyroid function tests can be modified by barbiturates and phenytoin.
There are contradictory reports as to whether the clinical effect of Thyroxine is reduced. Thyroid function tests can be modified, without changes in clinical effect of Thyroxine, by rifampicin, salicylates, diazepam, heparin, fenclofenac, fenoprofen and flurbiprofen. Monitoring Of the many techniques applied to estimate optimal thyroid replacement therapy, among the more precise are radioimmunoassay of total and free T4, T3 and TSH, with or without TRH stimulus. Both the resin T3 uptake (RT3U) and free Thyroxine index (FT4I) may be helpful.
OVERDOSAGE
Symptoms: Within three to six days after ingestion, any or all of the 'symptoms and signs listed under PRECAUTIONS AND WARNINGS may become evident. They may progress to 'Thyroid storm" with hyperpyrexia, coma and subsequent death.
Treatment
Early treatment has included gastric lavage, induced emesis and ingestion of activated charcoal. Induction of hypothermia has been used to reduce hyperpyrexia occurring later on In the clinical course. Of various adrenergic beta-blockers, propranotol has been used commonly to control cardiac arrhythmia and other manifestations. Reserpine, guanethidine and digoxin have also been used. Exchange transfusion has been recommended for progressive deterioration.
FURTHER INFORMATION
Pharmacology
Thyrox is synthetic Thyroxine sodium which can replace natural Thyroxine (Thyrox) the principal hormone in thyroglobulin (Tg) produced by the normal thyroid gland. It is well but variably absorbed (42-74%) and is bound by Thyroxine binding globulin (TBG), Thyroxine binding prealbumin (TBPA) and albumin, with about 0.03 to 0.05% remaining as free T4. About one third of ingested T4 is converted to triiodothyronine (T3) by deiodination in peripheral tissues. T3 is also protein bound but less avidly than T4 with about 0.2 to 0.5% remaining in the free state. Circulating T4 , and T3 levels influence the hypothalamic release of thyrotropin releasing hormone (TRH) which in turn influences the release of thyrotropin or thyroid stimulating hormone (TSH) which directly control activity of the thyroid gland. T4 plasma half life is about six to seven days whereas that of T3 is approximately two days.
Conjugation in, and clearance by the liver occurs, with no good evidence of a functional enterohepatic circulation. Both free drug and conjugates are found in urine. Variable absorption and deconjugation in the gastrointestinal tract leads to about 20 to 40% recovery of L-Thyroxine from stools. There is controversy about the passage of T4 and TSH across the placenta but not about the passage of TRH. There is controversy about the secretion of T4 and T3 in human breast milk, but the presence of both has been demonstrated. The maximum clinical effect of oral T4 appears in about nine days with an estimated reduction to half maximum effect in 11 to 15 days. Thyrox either directly or by conversion to T3 influences protein synthesis and development of the nervous system; has calorigenic effects; influences the cardiovascular system and influences carbohydrate, fat and cholesterol metabolism.
PHARMACEUTICAL PRECAUTIONS
Store at below 30 C in a dry place protected from light. Keep out of reach of children.
COMMERCIAL PACK
Thyrox 25 mcg Tablet: Each box contains 6 X 10 tablets in Alu-Alu Blister pack.
Thyrox 50 mcg Tablet: Each box contains 6 X 10 tablets in Alu-Alu Blister pack.
Thyrox 75 mcg Tablet: Each box contains 6 X 10 tablets in Alu-Alu Blister pack.
Thyrox 100 mcg Tablet: Each box contains 6 X 10 tablets in Alu-Alu Blister pack.