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Medical Disclaimer: This information is for educational purposes only and is not a substitute for professional medical advice.
Brand Name
Np Thyroid 15
Generic Name
Levothyroxine, Liothyronine
Active Ingredient
LevothyroxineCategory
l-Thyroxine [EPC]
Salt Form
Sodium
Variants
3
Different strengths and dosage forms
| Strength | Form | Route | NDC |
|---|---|---|---|
| 9.5 ug/1 | TABLET | ORAL | 76420-566 |
| 9.5 ug/1 | TABLET | ORAL | 63629-8265 |
| 9.5 ug/1 | TABLET | ORAL | 42192-327 |
This page is for informational purposes only and does not replace medical advice. Before using any prescription or over-the-counter medication for Np Thyroid 15, you must consult a qualified healthcare professional.
Detailed information about Np Thyroid 15
Levothyroxine is a synthetic form of the thyroid hormone thyroxine (T4), primarily used to treat hypothyroidism and suppress thyroid-stimulating hormone in thyroid cancer management. It belongs to the l-Thyroxine pharmacological class.
The dosage of levothyroxine is highly individualized and is based on several factors, including the patient's age, body weight, cardiovascular status, and the underlying cause of the hypothyroidism. For a healthy adult with no cardiovascular disease, the typical full replacement dose is approximately 1.6 micrograms (mcg) per kilogram of body weight per day (e.g., roughly 100-125 mcg/day for a 70 kg adult).
In cases of mild or subclinical hypothyroidism, healthcare providers may start with a lower dose, such as 25-50 mcg once daily. Doses are typically adjusted in increments of 12.5 to 25 mcg every 4 to 6 weeks until the patient's TSH levels are within the target reference range. For TSH suppression in thyroid cancer, higher doses may be required to drive TSH levels below 0.1 mIU/L.
Levothyroxine is approved for use in children and is critical for preventing neurodevelopmental delays in infants with congenital hypothyroidism. Dosing in children is generally higher per kilogram of body weight than in adults because of their rapid growth and development.
Healthcare providers monitor pediatric patients closely to ensure that the dose supports normal linear growth and bone maturation without causing premature closure of the epiphyses (growth plates).
No specific dose adjustments are generally required for patients with kidney disease. However, since thyroid hormones affect renal blood flow and filtration, your doctor will monitor your kidney function and TSH levels closely.
While the liver is the primary site of T4 to T3 conversion, standard dosing is usually maintained in patients with liver disease. However, severe hepatic impairment may alter the protein binding of the hormone, necessitating more frequent monitoring.
In patients over the age of 65 or those with known heart disease, the starting dose is significantly lower—often 12.5 to 25 mcg per day. The 'start low and go slow' approach is used to prevent putting excessive strain on the heart, which could lead to arrhythmias or angina (chest pain).
To ensure consistent absorption, levothyroxine must be taken under strict conditions:
If you miss a dose, take it as soon as you remember. However, if it is almost time for your next dose, skip the missed dose and return to your regular schedule. Do not take two doses at once to make up for a missed one. Because of the drug's long half-life, a single missed dose is unlikely to cause immediate symptoms, but chronic inconsistency will lead to unstable TSH levels.
An overdose of levothyroxine can cause a state of 'thyrotoxicosis' (excessive thyroid hormone). Symptoms include a rapid or irregular heartbeat, chest pain, tremors, extreme nervousness, confusion, and heat stroke. In severe cases, it can lead to seizures or heart failure. If an overdose is suspected, contact a poison control center or seek emergency medical care immediately.
> Important: Follow your healthcare provider's dosing instructions exactly. Do not adjust your dose or stop taking the medication without explicit medical guidance, as this can lead to a recurrence of symptoms or serious health complications.
Most side effects of levothyroxine are actually symptoms of 'iatrogenic hyperthyroidism'—meaning they occur because the dose is slightly too high for the body's needs. When the dose is perfectly calibrated, side effects are rare. Common symptoms of excessive replacement include:
Levothyroxine is a lifelong medication for most patients. It has a narrow therapeutic index, meaning that even small changes in the amount of drug in your system can lead to significant health consequences. Patients must be aware that this is not a 'cure' for hypothyroidism but a replacement for a hormone the body can no longer produce. Consistency in how and when you take the medication is the cornerstone of safe therapy.
The FDA has issued a Black Box Warning stating that levothyroxine should never be used as a tool for weight loss or to treat obesity. In individuals with normal thyroid function, taking levothyroxine will not result in weight loss and can lead to dangerous cardiac events, especially if combined with diet pills or stimulants.
While few drugs are strictly contraindicated, the use of levothyroxine with uncompensated adrenal insufficiency is a clinical contraindication. Additionally, using it alongside high-dose sympathomimetics (like certain weight loss drugs) is dangerous due to the risk of cardiac arrest.
There are three primary conditions where levothyroxine must not be used:
Levothyroxine is considered safe and essential during pregnancy (FDA Category A). Thyroid hormone is critical for the neurological development of the fetus, especially in the first trimester before the baby's own thyroid begins to function.
Small amounts of thyroid hormone are excreted into breast milk. However, this is not known to cause any adverse effects on the nursing infant. Levothyroxine is considered compatible with breastfeeding. Maintaining normal thyroid levels in the mother is also important for maintaining an adequate milk supply.
Levothyroxine is a synthetic L-isomer of thyroxine (T4). Its primary mechanism is the activation of nuclear thyroid hormone receptors. Once T4 is converted to T3 (the active form) by 5'-deiodinase enzymes, T3 enters the cell and the nucleus. It binds to thyroid hormone receptors (TR) which are attached to thyroid response elements (TRE) on the DNA. This binding acts as a 'switch' for gene transcription. It increases the expression of genes responsible for the production of Na+/K+ ATPase (the sodium-potassium pump), beta-adrenergic receptors, and various metabolic enzymes. This results in an increase in the basal metabolic rate and heat production (thermogenesis).
Common questions about Np Thyroid 15
Levothyroxine is primarily used as a replacement therapy for patients with hypothyroidism, a condition where the thyroid gland does not produce enough thyroid hormone. It is also used to treat or prevent goiter (enlarged thyroid gland) and as part of the treatment for certain types of thyroid cancer by suppressing Thyroid-Stimulating Hormone (TSH). By providing a synthetic version of the hormone T4, it helps restore the body's normal metabolic rate. This medication is usually a lifelong treatment because most causes of hypothyroidism are permanent. It is not intended for use in weight loss or treating obesity in patients with normal thyroid function.
The most common side effects of levothyroxine are typically symptoms of having too much thyroid hormone in the system, often called hyperthyroidism. These include heart palpitations, tremors, nervousness, anxiety, and heat intolerance. Patients may also experience increased sweating, weight loss, or difficulty sleeping. If the dose is correctly adjusted by a healthcare provider, most patients experience few to no side effects. However, if you feel like your heart is racing or you are excessively shaky, it may be a sign that your dose needs to be lowered. Always report these symptoms to your doctor for a TSH blood test.
There is no known direct interaction between alcohol and levothyroxine that would make the medication dangerous. However, alcohol can affect your overall metabolic health and liver function, which is where a significant portion of thyroid hormone conversion takes place. Excessive drinking can also lead to inconsistent medication habits, such as forgetting to take your dose on an empty stomach. For the best results, it is recommended to consume alcohol only in moderation. If you have underlying liver issues, you should discuss alcohol use with your doctor as it may complicate your thyroid management. Consistency in your daily routine is key to maintaining stable hormone levels.
Yes, levothyroxine is not only safe but absolutely essential during pregnancy for women with hypothyroidism. Thyroid hormone is critical for the healthy development of the baby's brain and nervous system, especially in the first trimester. Most women require a dose increase of 25% to 50% as soon as they become pregnant to meet the increased demands of the fetus. Untreated hypothyroidism during pregnancy can lead to serious complications like preeclampsia, miscarriage, or developmental delays in the child. If you are planning to become pregnant or find out you are pregnant, contact your doctor immediately to have your TSH levels checked and your dose adjusted.
While you may start to feel a slight improvement in your energy levels within 1 to 2 weeks, it typically takes 4 to 6 weeks for levothyroxine to reach a steady state in your body and for your symptoms to significantly improve. This is because the drug has a very long half-life and takes time to build up in your tissues. Doctors usually wait at least 6 weeks after starting the medication or changing the dose before checking your TSH levels. It is important to be patient and continue taking the medication even if you do not feel better immediately. Full resolution of symptoms like skin changes or hair thinning may take several months of stable hormone levels.
You should never stop taking levothyroxine suddenly without consulting your healthcare provider. Since the medication replaces a hormone that your body can no longer produce, stopping it will cause your metabolism to slow down again, leading to a return of hypothyroid symptoms. These symptoms, such as extreme fatigue, depression, and cold intolerance, can return gradually over several weeks as the drug leaves your system. In severe cases, stopping the medication can lead to a dangerous condition called myxedema coma. If you are experiencing side effects, your doctor will help you adjust the dose safely rather than stopping the treatment entirely.
If you miss a dose of levothyroxine, take it as soon as you remember that same day. If you don't remember until the next day, simply take your scheduled dose for that day and do not double up. Because levothyroxine stays in your system for a long time, a single missed dose is unlikely to cause a major problem or immediate symptoms. However, frequent missed doses will cause your TSH levels to fluctuate, which can make you feel unwell and complicate your treatment plan. To avoid missing doses, try taking your medication at the same time every morning, perhaps by keeping it on your nightstand with a glass of water.
Levothyroxine itself does not cause weight gain; in fact, it is used to treat the weight gain that often occurs with an underactive thyroid. When your thyroid levels are too low, your metabolism slows down, which can lead to weight gain. By restoring your thyroid levels to normal, levothyroxine should help your metabolism return to its natural state, which often helps with weight loss or weight maintenance. However, some patients may experience an increase in appetite as they start to feel better, which could lead to weight gain if not managed. If you are gaining weight while taking levothyroxine, it may be a sign that your dose is still too low or that other lifestyle factors are involved.
Levothyroxine can be taken with other medications, but many drugs and supplements can interfere with its absorption. Common items like calcium supplements, iron pills, antacids, and even multivitamins can bind to levothyroxine in your stomach, preventing it from entering your bloodstream. To avoid this, you should take levothyroxine at least 4 hours apart from these supplements. Other medications, like certain blood thinners or diabetes drugs, may require dose adjustments when you start or change your thyroid medication. Always provide your doctor and pharmacist with a complete list of everything you take, including over-the-counter products and herbal supplements, to ensure there are no dangerous interactions.
Yes, levothyroxine is widely available as a generic medication and is typically much less expensive than brand-name versions like Synthroid or Tirosint. While the active ingredient is the same, different manufacturers may use different fillers or dyes, which can slightly change how the drug is absorbed by your body. Because levothyroxine has a narrow therapeutic index, even a small change in absorption can affect your TSH levels. Most endocrinologists recommend sticking with the same manufacturer once your TSH is stable. If your pharmacy switches your generic brand, you should have your TSH levels checked again in about 6 weeks to ensure the new version is working just as well for you.
Other drugs with the same active ingredient (Levothyroxine)
These effects may occur as the body adjusts to the medication or if the dose is moderately high:
> Warning: Stop taking Levothyroxine and call your doctor immediately if you experience any of these serious cardiovascular or allergic symptoms.
Prolonged use of levothyroxine at doses that suppress TSH below normal levels can lead to two significant long-term health issues:
Thyroid hormones, including levothyroxine, either alone or with other therapeutic agents, should not be used for the treatment of obesity or for weight loss. In euthyroid patients (those with normal thyroid function), doses within the range of daily hormonal requirements are ineffective for weight reduction. Larger doses may produce serious or even life-threatening manifestations of toxicity, particularly when given in association with sympathomimetic amines such as those used for their anorectic (appetite suppressant) effects.
Report any unusual symptoms or changes in your health to your healthcare provider immediately to ensure your dose remains in the safe therapeutic window.
Regular laboratory testing is the only way to ensure the safety of levothyroxine therapy.
Levothyroxine generally does not interfere with the ability to drive or operate machinery. However, if you are experiencing tremors, nervousness, or dizziness due to a dose that is too high, you should exercise caution until your levels are stabilized.
There is no direct interaction between alcohol and levothyroxine. However, excessive alcohol consumption can affect liver function, which may indirectly influence how your body converts T4 to T3. Moderation is advised.
Do not stop taking levothyroxine abruptly. Because it is a replacement for a vital hormone, stopping it will cause your hypothyroid symptoms to return, often more severely. There is no 'withdrawal syndrome' in the traditional sense, but your metabolism will crash, leading to extreme fatigue, depression, and potentially myxedema. If discontinuation is necessary (e.g., for certain medical tests), it must be done under strict medical supervision.
> Important: Discuss all your medical conditions, especially heart problems, diabetes, or adrenal issues, with your healthcare provider before starting Levothyroxine.
Food is the most common 'interactor' with levothyroxine.
Certain drugs can change the levels of thyroxine-binding globulin (TBG), which affects the 'Total T4' measurement but not necessarily the 'Free T4.' These include estrogens (including birth control pills), which increase TBG, and androgens or anabolic steroids, which decrease TBG. Always tell your doctor if you start or stop hormonal therapy.
> Important: Tell your doctor about ALL medications, supplements, and herbal products you are taking, as many common items can prevent this medication from working correctly.
These are conditions where the drug should be used with extreme caution:
Patients with known hypersensitivity to any of the inactive ingredients in the specific brand of levothyroxine (such as lactose, corn starch, or specific color dyes like Tartrazine/FD&C Yellow No. 5) should use an alternative formulation. Gel capsules (Tirosint) are often used for patients with multiple sensitivities as they contain the fewest excipients.
> Important: Your healthcare provider will evaluate your complete medical history, including heart health and adrenal function, before prescribing Levothyroxine.
Levothyroxine is the standard of care for congenital and acquired hypothyroidism in children. The goal is to rapidly restore normal TSH and T4 levels to ensure normal physical and mental development.
Patients over 65 are more sensitive to the effects of thyroid hormone, particularly on the heart and bones.
While no specific dose reduction is mandated for renal impairment, the clearance of many drugs is altered in kidney disease. Patients on dialysis may have fluctuating thyroid hormone levels and require more frequent TSH monitoring.
In patients with cirrhosis or hepatitis, the liver's ability to produce thyroxine-binding globulin (TBG) and convert T4 to T3 may be impaired. While the dose of levothyroxine usually stays the same, the 'Total T4' lab result may be misleadingly low, making 'Free T4' and TSH the more reliable markers for these patients.
> Important: Special populations, particularly pregnant women and the elderly, require individualized medical assessment and frequent lab monitoring.
| Parameter | Value |
|---|---|
| Bioavailability | 64% to 80% (Fasting) |
| Protein Binding | >99% (TBG, TTR, Albumin) |
| Half-life | 6 to 7 days (Euthyroid) |
| Tmax | 2 to 4 hours |
| Metabolism | Liver (Deiodination, Glucuronidation) |
| Excretion | Renal (approx. 80%), Fecal (approx. 20%) |
Levothyroxine is the cornerstone of the l-Thyroxine [EPC] class. It is categorized as a thyroid hormone replacement. Unlike liothyronine (synthetic T3), which has a short half-life and causes rapid peaks in hormone levels, levothyroxine provides a stable, long-acting reservoir that the body can convert into T3 as needed, making it the preferred physiological choice for long-term therapy.