Thyrin 50

Indications

For the treatment of hypothyroidism of any cause except transient hypothyroidism during the recovery phase of subacute Thyroiditis.

To lower Thyroid Stimulating Hormone (TSH) levels in cases of goiters, nodules, and post-radiological or surgical treatment of Thyroid cancer.

To counteract goitrogenic effects induced by medications like Lithium.

As a diagnostic tool in suppression tests.

Pharmacology

This tablet comprises synthetic Levothyroxine, also known as Thyroxine or T4, identical to the natural hormone produced in the Thyroid gland. Approximately 30% of T4 converts to the more active Triiodothyronine (T3) in peripheral tissues. TBG (Thyroxine Binding Globulin) predominantly carries T4, shielding it from metabolism and excretion, resulting in a prolonged half-life in circulation. T4’s elimination half-life is 6 to 7 days, shortened to 3 or 4 days in hyperthyroidism and extended to 9 to 10 days in hypothyroidism. T4 degradation primarily occurs in the liver, where it is conjugated and excreted in urine. With its long half-life, a steady blood level of the biologically active T3 can be achieved with a single daily dose of Levothyroxine, ensuring consistent therapeutic effects once the correct dosage is determined.

Dosage & Administration

Adult dose:
Initial dose: 25-50 mcg/day, with gradual increments every 6-8 weeks as necessary. Adjustments are typically made in 12.5-25 mcg increments until clinical euthyroidism is achieved and serum TSH normalizes.

Severe hypothyroidism:
Start with 12.5-25 mcg/day, increasing by 25 mcg/day every 2-4 weeks until TSH normalization.

Secondary or tertiary hypothyroidism:
Titrate Levothyroxine dosage to achieve clinical euthyroidism and restore serum free-T4 to the upper half of the normal range.

Pediatric Dosage:
Newborns: Start with 10-15 mcg/kg/day, adjust as needed based on clinical and laboratory response. Infants and Children: Begin with 25 mcg/day, increasing gradually to desired effect.

Interactions

Concurrent use of tri/tetracyclic antidepressants and Thyrin may amplify therapeutic and toxic effects. Careful monitoring is warranted, especially when initiating, altering, or discontinuing thyroid therapy alongside antidiabetic medications or insulin.

Contraindications

Avoid in untreated Thyrotoxicosis, acute Myocardial Infarction, and uncorrected Adrenal failure.

Side Effects

Adverse reactions to Thyrin therapy mimic hyperthyroidism symptoms due to overdosage. These include fatigue, increased appetite, weight loss, heat intolerance, palpitations, tremors, and gastrointestinal disturbances.

Pregnancy & Lactation

Pregnancy may increase Levothyroxine requirements. While minimal excretion occurs in human milk, caution is advised during lactation. Adequate replacement doses are crucial for maintaining normal lactation.

Precautions & Warnings

In patients with hypothyroidism due to decreased pituitary function, concurrent adrenocortical insufficiency may be present, necessitating corticosteroid replacement before initiating Thyrin therapy. Exercise caution in patients with cardiovascular disease or severe hypothyroidism to prevent adverse events.

Overdose Effects

Overdose symptoms resemble hyperthyroidism manifestations and require prompt intervention. Dose adjustment or temporary discontinuation may be necessary if signs of overdosage occur.

Therapeutic Class

Thyroid drugs & hormones

Storage Conditions

Keep below 30°C in a dry place, shielded from light, and out of children’s reach.