NP Thyroid 90

Uses

Hypothyroidism: As replacement or supplemental therapy in congenital or acquired hypothyroidism of any etiology, except transient hypothyroidism during the recovery phase of subacute-thyroiditis.

Specific indications: Primary (thyroidal), secondary (pituitary), and tertiary (hypothalamic) hypothyroidism and subclinical hypothyroidism.

Pituitary TSH Suppression: In the treatment or prevention of various types of euthyroid goiters, subacute or chronic lymphocytic thyroiditis (Hashimoto's thyroiditis), multinodular goiter and, as an adjunct to surgery and radioiodine therapy in the management of thyrotropin-dependent well-differentiated thyroid cancer.

Liothyronine is a thyroid hormone replacement therapy used to treat hypothyroidism, to suppress TSH, and to help in the diagnosis of hyperthyroidism.

Liothyronine is officially approved for the following indications:

• Replacement therapy in primary (thyroidal), secondary (pituitary) and tertiary (hypothalamic) congenital or acquired hypothyroidism.

• As an adjunct therapy to surgery and radioiodine in the management of thyroid cancer.

• As a diagnostic agent in suppression tests for mild hyperthyroidism or thyroid gland autonomy.

In general terms, exogenous liothyronine is used to replace insufficient hormonal production and restore T3 plasma levels.

The lack of liothyronine can be presented as a pale and puffy face, coarse, brittle hair, dry skin, croaky voice and constipation as well as irregular periods, drowsiness, and lethargy.

Liothyronine should never be used in the suppression of benign nodules and nontoxic diffuse goiter in iodine-sufficient patients nor in the treatment of hyperthyroidism during the recovery phase of subacute thyroiditis.

NP Thyroid 90 is also used to associated treatment for these conditions: Adiposity, Cellulite, Hypothyroidism, Myxedema coma, Euthyroid Goitre, Thyrotropin dependent Thyroid cancerAutonomy of thyroid gland, Hyperthyroidism, Hypothyroidism, Myxedema coma, Thyroid Cancers, Euthyroid Goitre, Myxedema pre-coma, Supplemental or replacement therapy

How NP Thyroid 90 works

Levothyroxine is a synthetically prepared levo-isomer of the thyroid hormone thyroxine (T₄, a tetra-iodinated tyrosine derivative) that acts as a replacement in deficiency syndromes such as hypothyroidism. T₄ is the major hormone secreted from the thyroid gland and is chemically identical to the naturally secreted T₄: it increases metabolic rate, decreases thyroid-stimulating hormone (TSH) production from the anterior lobe of the pituitary gland, and, in peripheral tissues, is converted to T₃. Thyroxine is released from its precursor protein thyroglobulin through proteolysis and secreted into the blood where is it then peripherally deiodinated to form triiodothyronine (T₃) which exerts a broad spectrum of stimulatory effects on cell metabolism. T₄ and T₃ have a relative potency of ~1:4.

Thyroid hormone increases the metabolic rate of cells of all tissues in the body. In the fetus and newborn, thyroid hormone is important for the growth and development of all tissues including bones and the brain. In adults, thyroid hormone helps to maintain brain function, food metabolism, and body temperature, among other effects. The symptoms of thyroid deficiency relieved by levothyroxine include slow speech, lack of energy, weight gain, hair loss, dry thick skin and unusual sensitivity to cold.

The thyroid hormones have been shown to exert both genomic and non-genomic effects. They exert their genomic effects by diffusing into the cell nucleus and binding to thyroid hormone receptors in DNA regions called thyroid hormone response elements (TREs) near genes. This complex of T₄, T₃, DNA, and other coregulatory proteins causes a conformational change and a resulting shift in transcriptional regulation of nearby genes, synthesis of messenger RNA, and cytoplasmic protein production. For example, in cardiac tissues T₃ has been shown to regulate the genes for α- and β-myosin heavy chains, production of the sarcoplasmic reticulum proteins calcium-activated ATPase (Ca2+-ATPase) and phospholamban, β-adrenergic receptors, guanine-nucleotide regulatory proteins, and adenylyl cyclase types V and VI as well as several plasma-membrane ion transporters, such as Na+/K+–ATPase, Na+/Ca2+ exchanger, and voltage-gated potassium channels, including Kv1.5, Kv4.2, and Kv4.3. As a result, many cardiac functions including heart rate, cardiac output, and systemic vascular resistance are closely linked to thyroid status.

The non-genomic actions of the thyroid hormones have been shown to occur through binding to a plasma membrane receptor integrin aVb3 at the Arg-Gly-Asp recognition site. From the cell-surface, T₄ binding to integrin results in down-stream effects including activation of mitogen-activated protein kinase (MAPK; ERK1/2) and causes subsequent effects on cellular/nuclear events including angiogenesis and tumor cell proliferation.

Liothyronine replaces endogenous thyroid hormone and then exerts its physiologic effects by controlling DNA transcription and protein synthesis. This effect on DNA is obtained by the binding of liothyronine to the thyroid receptors attached to DNA. Exogenous liothyronine exerts all the normal effects of the endogenous thyroid T3 hormone. Hence, it increases energy expenditure, accelerates the rate of cellular oxidation stimulating growth, maturation, and metabolism of the body tissues, aids in myelination of nerves and development of synaptic processes in the nervous system and enhances carbohydrate and protein metabolism.

Dosage

NP Thyroid 90 dosage

In order to avoid irregular absorption, Levothyroxine should be taken preferably at a fixed time on an empty stomach. Concomitant intake of food may decrease the absorption of Levothyroxine. Dosing must be individualized and adjustments to be made based on periodic assessment of the patient's clinical response and laboratory parameters.

Adult Dosage:

Initial starting dose: 25-50 mcg/day, with gradual increments in dose at 6-8 week intervals, as needed. The Levothyroxine Sodium dose is generally adjusted in 12.5-25 mcg 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 mcg/day with increases of 25 mcg/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 - T 4 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 mcg/kg/day.

TSH suppression: For thyrotropin-dependent well-differentiated thyroid cancer: Doses >2 mcg/kg/day may be given as a single dose to suppress TSH to <0.1 MIU/L. For benign nodules and nontoxic multinodular goitre: Target TSH is generally higher at 0.1-0.5 MIU/L for nodules and 0.5-1 MIU/L for multinodular goitre.

Pediatric Dosage:

Newborns: The recommended starting dose is 10-15 mcg/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 T 4 concentrations, the recommended initial starting dose is 50 mcg/day of Levothyroxine Sodium.

Infants and Children: In children with chronic or severe hypothyroidism, initial dose of 25 mcg/day with increments of 25 mcg 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.

Daily dose per kg body weight:

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

The dose should be adjusted based on clinical response and laboratory parameters.

Side Effects

Adverse reactions associated with Levothyroxine therapy are primarily those of hyperthyroidism due to therapeutic overdose. They include the following:

• General: Fatigue, increased appetite, weight loss, heat intolerance, fever, excessive sweating
• Central nervous system: headache, hyperactivity, nervousness, anxiety, irritability, emotional lability, insomnia
• Musculoskeletal: Tremors, muscle weakness
• Cardiovascular: Palpitations, tachycardia, arrhythmias, increased pulse and blood pressure
• Respiratory: Dyspnea
• Gastrointestinal: Diarrhea, vomiting, abdominal cramps
• Dermatologic: Hair loss, flushing

Toxicity

LD₅₀=20 mg/kg (orally in rat). Hypermetabolic state indistinguishable from thyrotoxicosis of endogenous origin. Symptoms of thyrotoxicosis include weight loss, increased appetite, palpitations, nervousness, diarrhea, abdominal cramps, sweating, tachycardia, increased pulse and blood pressure, cardiac arrhythmias, tremors, insomnia, heat intolerance, fever, and menstrual irregularities.

The reported oral LD50 of liothyronine in the rat is higher than 4540 mg/kg. When overdosage is registered, symptoms of hyperthyroidism are reported as well as confusion, disorientation, cerebral embolism, seizure, shock, coma, and death. The symptoms of overdose can be presented immediately or several days after overdose ingestion. In an overdose state, reduce the dose of liothyronine and do supportive treatment.

There are no reports studying the carcinogenic, and mutagenic potential nor on the effects of liothyronine on fertility.

Precaution

Levothyroxine has a narrow therapeutic index. So, careful dosage titration is necessary to avoid the consequences of over- or under-treatment. Caution is needed when administering Levothyroxine to patients with cardiovascular disorders, to the elderly in whom there is an increased risk of occult cardiac disease & for patients with nontoxic diffuse goiter or nodular thyroid disease in order to prevent precipitation of thyrotoxicosis

Interaction

Concurrent use of tri/tetracyclic antidepressants and Levothyroxine may increase the therapeutic and toxic effects of both drugs, possibly due to increased receptor sensitivity to catecholamines. Toxic effects may include increased risk of cardiac arrhythmias and CNS stimulation; onset of action of tricyclics may be accelerated. Administration of sertraline in patients stabilized on Levothyroxine may result in increased Levothyroxine requirements. Addition of Levothyroxine to antidiabetic or insulin therapy may result in increased antidiabetic agent or insulin requirements. Careful monitoring of diabetic control is recommended, especially when thyroid therapy is started, changed, or discontinued. Serum digitalis glycoside levels may be reduced in hyperthyroidism or when the hypothyroid patient is converted to the euthyroid state. Therapeutic effect of digitalis glycosides may be reduced.

Volume of Distribution

The reported volume of distribution of liothyronine is reported to be of 0.1-0.2 L/kg.

Elimination Route

Absorption of orally administered T4 from the gastrointestinal tract ranges from 40% to 80% with the majority of the levothyroxine dose absorbed from the jejunum and upper ileum. T4 absorption is increased by fasting, and decreased in malabsorption syndromes and by certain foods such as soybeans, milk, and dietary fiber. Absorption may also decrease with age. In addition, many drugs affect T4 absorption including bile acide sequestrants, sucralfate, proton pump inhibitors, and minerals such as calcium (including in yogurt and milk products), magnesium, iron, and aluminum supplements. To prevent the formation of insoluble chelates, levothyroxine should generally be taken on an empty stomach at least 2 hours before a meal and separated by at least 4 hours from any interacting agents.

Thyroid hormones are well absorbed orally. From these hormones, liothyronine is almost completely absorbed and it does not present changes in the absorption rate due to concomitant administration of food.liothyronin Multiple administration of 50 mcg of liothyronine provided a maximal plasma concentration of total T3 of 346 ng/dL in about 2.5 hours with an AUC of 4740 ng.h/dL.

Half Life

T₄ half-life is 6 to 7 days. T₃ half-life is 1 to 2 days.

The half-life of liothyronine is reported to be between 1 and 2 days.

Clearance

There are no reports obtaining this value specifically.

Elimination Route

Thyroid hormones are primarily eliminated by the kidneys. A portion of the conjugated hormone reaches the colon unchanged and is eliminated in the feces. Approximately 20% of T₄ is eliminated in the stool. Urinary excretion of T₄ decreases with age.

The main elimination of thyroid hormones is known to be done via the kidneys from which less than 2.5% of the excreted drug is represented by the unchanged drug. This elimination route is reduced with age. A portion of the metabolic products of liothyronine is excreted to the bile and gut where they can be part of enterohepatic recirculation.

Pregnancy & Breastfeeding use

Pregnancy Category A. Pregnancy may increase Levothyroxine requirements. Although thyroid hormones are excreted only minimally in human milk, caution should be exercised when it is administered to a nursing woman. However, adequate replacement doses of Levothyroxine are generally needed to maintain normal lactation.

Contraindication

Untreated subclinical or overt thyrotoxicosis of any etiology and acute myocardial infarction.

Acute Overdose

The signs and symptoms of overdose are those of hyperthyroidism – agitation, confusion, irritability, hyperactivity, headache, sweating, mydriasis, tachycardia, arrhythmias, tachypnoea, pyrexia, increased bowel movements and convulsions. Cerebral embolism, shock, coma, and death have been reported. Symptoms may not necessarily be evident or may not appear until several days after ingestion of Levothyroxine Sodium.

Treatment of Overdose: Levothyroxine Sodium should be reduced in dose or temporarily discontinued if signs or symptoms of overdosage occur. Treatment is symptomatic.

Storage Condition

Store in a cool place, protect from light & moisture.

Innovators Monograph

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