Thyronor 50

Generic

Levothyroxine Sodium

 

Indications

• As a replacement therapy for hypothyroidism caused by any cause. During the healing period of subacute Thyroiditis, replacement medication should not be started for transitory hypothyroidism.
• In the presence of goitres, nodules, and following radiological and/or surgical therapy of Thyroid cancer, to lower Thyroid Stimulating Hormone (TSH) levels.
• For the suppression of other medications' goitrogenic effects, such as lithium.
• In suppression testing as a diagnostic help.

 

Pharmacology

This tablet includes synthetic Levothyroxine (commonly known as Thyroxine or T4), which is the same as the natural thyroid hormone T4. In peripheral tissues, about 30% of T4 is transformed to the far more active Triiodothyronine (T3). The principal carrier of T4 is TBG (Thyroxine Binding Globulin). T4 is protected from metabolism and excretion by this binding, resulting in an extended half-life in circulation. Unbound T4 makes up only 0.03 percent of total T4 in plasma. T4 has a half-life of 6 to 7 days in the body. The half-life in hyperthyroidism is 3 or 4 days, whereas in hypothyroidism it can be 9 to 10 days. The half-life of T4 may be shortened under situations associated with low protein in plasma, such as nephrosis or hepatic cirrhosis, or when binding to protein is blocked by specific medications. Thyroid hormones are primarily broken down in the liver. T4 is eliminated in the urine after being conjugated with Glucuronic and Sulphate conjugates via the Phenolic hydroxyl group. Thyroid hormones have an enterohepatic circulation because they are released and reabsorbed after hydrolysis in the intestine. Because of T4's lengthy half-life, a single daily dose of Levothyroxine can provide a stable blood level of the biologically more active T3.

 

Dosage & Administration

Adult dose:

• Initial starting dose: 25-50 meg/day, with gradual increments in dose at 6-8 week intervals, as needed. The Levothyroxine Sodium dose is generally adjusted in 12.5-25 meg increments until the patient with primary hypothyroidism is clinically euthyroid and the serum TSH has normalized.
• In patients with severe hypothyroidism: Initial dose is 12.5-25 meg/day with increases of 25 meg/day every 2-4 weeks, accompanied by clinical and laboratory assessment,until the TSH level is normalized.
• In patients with secondary (pituitary) or tertiary (hypothalamic)
• hypothyroidism: Levothyroxine Sodium dose should be titrated until the patient is clinically euthyroid and the serum free - T4 level is restored to the upper half of the normal range.
• For patients older than 50 years or for patients under 50 years of age with underlying cardiac disease: 1.7 meg/kg/day.

Pediatric Dosage Newborns: The recommended starting dose is 10-15 meg/kg/day. A lower starting dose should be considered in infants at risk for cardiac failure and the dose should be increased in 4-6 weeks as needed based on clinical and laboratory response to treatment. In infants with very low (<5 mcg/dL) or undetectable serum T4 concentrations, the recommended initial starting dose is 50 meg/day of Levothyroxine Sodium.

Infants and Children: In children with chronic or severe hypothyroidism, initial dose of 25 meg/day with increments of 25 meg every 2-4 weeks until the desired effect is achieved. Hyperactivity in an older child can be minimized if the starting dose is one-fourth of the recommended full replacement dose and the dose is then increased on a weekly basis by an amount equal to one-fourth the full recommended replacement dose until the full recommended replacement dose is reached.

• 0-3 months: 10-15 meg/kg/day
• 3-6 months: 8-10 meg/kg/day
• 6-12 months: 6-8 meg/kg/day
• 1-5 years: 5-6 meg/kg/day
• 6-12 years: 4-5 meg/kg/day
• >12 years but growth and puberty incomplete: 2-3 meg/kg/day
• Growth and puberty complete: 1.7 meg/kg/day.

The dose should be adjusted based on clinical response and laboratory parameters. In the treatment of goitres, nodules and Thyroid cancer, the objective is to ensure a constant and sufficient suppression of TSH. For suppression of TSH levels, a gradual increase in dosing is usually not necessary. For adults, the usual suppressive dosage of T4 is 2.6 meg/kg of body weight daily. When Levothyroxine Sodium is used as a diagnostic aid, the dosage depends on the type of investigation.

 

Interaction

Thyroid hormones taken together with any of the following medicines or substances may cause clinically significant interactions:

Oral anticoagulants: Thyroid hormones may help oral anticoagulants work better.

Anti-diabetic drugs: Thyroid hormones can increase the need for insulin or oral hypoglycemic medications.

Digitalis preparations: Thyroid hormones may change the amount of Digitalis you need. Cholestyramine: Cholestyramine may reduce the absorption of thyroid hormones; consequently, there should be at least a 4-hour gap between administrations.

Phenytoin: Phenytoin appears to improve thyroid hormone metabolism and may displace T4 from TBG.

Foods: To avoid uneven absorption, Levothyroxine pills should be taken on an empty stomach with some fluids at a set time. T4 absorption may be reduced if food is consumed at the same time.

 

Contraindications

Acute Myocardial Infarction, Uncorrected Adrenal Failure, Untreated preclinical or overt Thyrotoxicosis of any origin.

 

Side Effects

Overdosing can cause hyperthyroidism symptoms as tachycardia, agitation, tremor, headache, flushing, perspiration, and weight loss. Treatment can be stopped for a few days and then resumed at a lower dose if necessary.

 

Pregnancy & Lactation

Category A Pregnancy. The need for Levothyroxine may increase during pregnancy. Although thyroid hormones are excreted in small amounts in human milk, caution should be maintained when given to a nursing mother. To maintain regular lactation, however, appropriate replacement doses of Levothyroxine are usually required.

 

Precautions & Warnings

• There may be adrenocortical insufficiency in patients whose hypothyroidism is caused by a decline in pituitary gland function; this should be addressed with appropriate replacement with corticosteroids before initiating Levothyroxine therapy to avoid acute adrenal insufficiency.
• In patients with cardiovascular illness and/or severe and long-term hypothyroidism, the beginning dose and any subsequent dose increases should be carefully considered.
• Angina, arrhythmias, myocardial infarction, cardiac failure, or a fast increase in blood pressure may develop or worsen as a result of a high initial dose or a quick increase in dosing, especially in elderly patients.
• Any significant change in body weight while on T4 therapy necessitates dosage adjustments.
• When checking T3 and T4 levels in the blood, keep in mind that obtaining a normal T3 level will necessitate a "high" normal to slightly elevated T4 level.
• In primary hypothyroidism, the correct dosage of Levothyroxine should be determined by checking the TSH level in the blood to see if it has returned to normal.
• Because Thyroid preparations intoxication might have dangerous repercussions.

 

Therapeutic Class

Thyroid drugs & hormone

 

Storage Conditions

Protect from light and store in a cool, dry location. Keep out of children's reach.

 

Pharmaceutical Name

Nuvista Pharma Limited