Ptu vs Methimazole

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Table of Contents

Overview

PTU Information

Methimazole Information

Comparative Analysis

Overview

PTU Information

Methimazole Information

Comparative Analysis

Introduction

For patients with hyperthyroidism or other types of thyroid disorders, certain drugs that alter the function of the thyroid gland can help in managing symptoms and normalizing hormone levels. Propylthiouracil (PTU) and Methimazole are two such medications often prescribed for these conditions. They both inhibit the production of thyroid hormones, but their mechanism of action and side effects differ slightly. PTU inhibits both the synthesis and conversion of T4 to T3 inside cells which makes it more useful during a thyroid storm, a severe form of hyperthyroidism. Methimazole is generally preferred due to its longer half-life allowing for once-daily dosing, compared to PTU which requires multiple doses per day due to its shorter half-life. However, it only inhibits hormone synthesis without affecting peripheral conversion.

Ptu vs Methimazole Side By Side

Attribute	Not specified for ptu	Tapazole
Brand Name	Not specified for PTU	Tapazole
Contraindications	Should not be taken with iodine supplements or radiopharmaceutical agents that contain iodine. Requires regular liver function monitoring.	Should not be taken with iodine supplements or radiopharmaceutical agents that contain iodine.
Cost	For 60 tablets of 50 mg averages around $150-$200	For 30 tablets of 10 mg is approximately $70-$90
Generic Name	Propylthiouracil (PTU)	Methimazole
Most Serious Side Effect	Liver damage	Allergic responses, severe nausea/vomiting, swelling of glands/lymph nodes, unusual tiredness
Severe Drug Interactions	Not specified	Not specified
Typical Dose	50–300 mg/day, divided into three doses	10-30 mg/day, taken in a single dose

What is Ptu?

Propylthiouracil (the generic name for PTU) was one of the first antithyroid medications developed, which was a significant advancement over previous treatment options. It was initially approved by the FDA in 1947. PTU works by inhibiting the synthesis of thyroid hormones, effectively reducing their levels in the body, which is crucial for treating conditions like hyperthyroidism. Unlike other similar drugs, PTU also blocks the conversion of T4 to T3 within peripheral tissues, providing a second mechanism of action.

Methimazole (also known as Tapazole), on the other hand, came after and has largely replaced PTU due to its more favorable side effect profile and simpler dosing regimen. Methimazole primarily works by inhibiting thyroid hormone synthesis but does not block peripheral conversion like PTU does.

Both medicines are effective at managing hyperthyroid conditions; however, methimazole is generally better tolerated with fewer adverse effects than propylthiouracil.

What conditions is Ptu approved to treat?

PTU (Propylthiouracil) and Methimazole are both approved for the treatment of hyperthyroidism, a condition where the thyroid gland is overactive. However, their uses slightly differ:

PTU is typically used as an initial therapy to bring rapid control of hyperthyroidism symptoms.
Methimazole has longer duration of action and requires less frequent dosing than PTU, making it preferred for long-term management after initial control is achieved.
In pregnant women with hyperthyroidism during the first trimester, PTU is often chosen due to concerns about rare birth defects associated with methimazole. After the first trimester, switching from PTU to methimazole may be considered because of potential liver complications in mothers on sustained PTU therapy.

How does Ptu help with these illnesses?

Propylthiouracil (PTU) and Methimazole are both medications used to manage hyperthyroidism, a condition where the thyroid gland produces an excessive amount of hormones. They function by inhibiting the enzyme thyroperoxidase in the thyroid hormone synthesis pathway, which prevents iodine from being added onto tyrosine residues on thyroglobulin; this process is necessary for creating thyroid hormones T3 and T4.

By blocking this step in hormone production, PTU and Methimazole effectively reduce excess levels of circulating thyroid hormones, alleviating symptoms such as rapid heart rate, weight loss, nervousness or irritability associated with hyperthyroidism. It's noted that individuals with overactive thyroids have relatively higher levels of these hormones. Thus by decreasing them, PTU and Methimazole can limit the negative effects of hyperthyroidism helping patients manage their conditions effectively.

While both drugs operate through similar mechanisms to control an overactive thyroid gland, there are differences between them including side effect profiles and dosing regimens that may influence which medication is preferred for certain patient populations.

What is Methimazole?

Methimazole, also known by the brand name Tapazole, is an antithyroid medication that works to reduce the production of thyroid hormones. It accomplishes this by inhibiting the enzyme thyroperoxidase in thyroid cells, which plays a crucial role in synthesizing these hormones. Methimazole was first approved for use by the FDA in 1950 and has become a common choice among healthcare providers due to its effectiveness and longer half-life compared to other medications like PTU (Propylthiouracil). As with any medication, Methimazole does come with potential side effects such as nausea, vomiting or mild rash but its overall safety profile is generally considered more favorable than that of PTU. The actions of Methimazole on reducing excess levels of thyroid hormones can be particularly beneficial for treating conditions like hyperthyroidism and Graves' disease.

What conditions is Methimazole approved to treat?

Methimazole is an antithyroid medication that has been approved for use in the treatment of hyperthyroidism, a condition where the thyroid gland produces too much thyroid hormone. It works by inhibiting the production of these hormones thereby helping to restore normal hormone levels. This can help alleviate symptoms such as rapid heart rate, anxiety, excessive sweating and weight loss associated with this disorder.

How does Methimazole help with these illnesses?

Methimazole is a medication that effectively reduces the production of thyroid hormones, which play vital roles in body metabolism, heart rate regulation and digestion. Overproduction of these hormones can lead to conditions such as hyperthyroidism or Grave's disease. Methimazole works by inhibiting an enzyme known as thyroid peroxidase from catalysing the iodination of tyrosine residues in thyroglobulin, thereby decreasing the production of thyroid hormones. Its action on this specific process makes it effective for managing overactive thyroid disorders. While PTU also hinders the same enzymatic activity, methimazole is often preferred because of its longer half-life and fewer side effects. This allows for less frequent dosing—usually once a day compared with several times a day for PTU—which may improve patient adherence to medication regimen.

How effective are both Ptu and Methimazole?

Both propylthiouracil (PTU) and methimazole are antithyroid drugs that have proven effectiveness in managing hyperthyroidism, a condition characterized by an overactive thyroid gland. Both medications were introduced around the same time in the mid-20th century. They work by inhibiting the production of thyroid hormones, but their precise mechanisms differ slightly.

A 2007 double-blind clinical trial demonstrated that both PTU and methimazole effectively manage symptoms of hyperthyroidism with similar safety profiles.[1] However, this study also showed no significant difference in terms of efficacy between patients who received PTU and those who received methimazole.

According to a meta-analysis conducted in 2015,[2] it was suggested that while both drugs can alleviate symptoms within two weeks of treatment initiation, methimazole may be slightly more effective at reducing levels of thyroid-stimulating hormone receptor antibodies (TRAb). This makes it particularly beneficial for Graves' disease patients as TRAbs play a key role in causing the disease.

Nonetheless, while methimazole is generally considered as first-line therapy due to its longer half-life and lower incidence rates of severe side effects like liver damage compared to PTU,[3] there are specific circumstances where PTU might be preferred. For example, during pregnancy or breastfeeding - owing to less placental transfer and reduced concentration present in breast milk than Methimazole[4]. Furthermore, while rare, if major adverse reactions occur with one drug such as skin rash or agranulocytosis (a potentially serious reduction in white blood cell count), switching to another medication might be necessary[5].

References:

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At what dose is Ptu typically prescribed?

Oral dosages of Ptu (propylthiouracil) range from 50–300 mg/day, divided into three doses. However, studies have shown that a dosage of 100-150 mg/day is often sufficient in treating hyperthyroidism for most people. Children and adolescents may be started on lower dosages decided by their healthcare provider based on the child's weight. In either population, dosage can be increased after a few weeks if there is no response or decreased when thyroid levels normalize. The maximum dosage that should not be exceeded in any case is 900 mg/day.

On the other hand, oral dosages for Methimazole typically start at about 5–30mg/day taken once daily; however, your doctor might adjust this depending on your body's response to the medication. For children and adolescents, doses are calculated based on body weight and severity of condition as determined by their healthcare provider.

As always it would be best to consult with your healthcare provider to determine which medication and what dose would work best for you considering all factors including age, overall health status and specific medical conditions.

At what dose is Methimazole typically prescribed?

Methimazole treatment typically begins at a dosage of 10-30 mg/day, taken in a single dose. However, depending on the individual's thyroid hormone levels and response to treatment, this can be increased up to 60 mg/day. This larger dosage may be divided into three separate doses of 20 mg each and spaced out evenly throughout the day. If there is no significant response after several weeks of taking Methimazole at an initial lower dose, your physician may then suggest increasing it gradually until symptoms improve or thyroid hormone levels normalize.

What are the most common side effects for Ptu?

Compared to Methimazole, PTU (Propylthiouracil) might have the following side effects:

Upset stomach
Nausea and vomiting
Dizziness or drowsiness
Mild rash or itching
Joint or muscle pain
Changes in taste sensation
Hair loss,
Decreased sense of taste -Numbness in hands and feet.

In rare cases, both drugs can cause a decrease in blood cells that help your body fight infections. This can make it easier for you to bleed from an injury or get sick from being around others who are ill. However, these serious side effects occur less frequently with Methimazole than with PTU.

abstract image of a patient experiencing side effect

Are there any potential serious side effects for Ptu?

While Methimazole is often well-tolerated, it can occasionally come with potentially serious side effects such as:

Signs of liver problems like dark urine, feeling tired, not hungry, upset stomach or stomach pain, light-colored stools, throwing up or yellow skin/eyes
Fever
Sore throat
Weakness on one side of the body
Trouble speaking or thinking
Change in balance
Blurred eyesight or loss of vision
Any unexplained bruising or bleeding
Enlarged lymph nodes

Other severe reactions might include:

Aplastic anemia and agranulocytosis (severe reduction in blood cells that help the body fight off infections)
Hypothyroidism (under active thyroid)

Should you experience any of these symptoms while taking Methimazole, stop using this medication immediately and consult your doctor.

What are the most common side effects for Methimazole?

Methimazole can have a range of side effects, some of which are:

Nausea and vomiting
Stomach upset or discomfort
Headache, dizziness
Mild rash or itching
Muscle pain or joint ache
Changes in taste sensation
Hair loss, changes in skin coloration These potential side effects do not affect everyone and usually subside as your body adjusts to the medication. However, more serious but less common side effects like severe nausea/vomiting, swelling of the glands/lymph nodes, unusual tiredness could occur indicating that you should seek immediate medical attention.

Are there any potential serious side effects for Methimazole?

While Methimazole is a common medication for hyperthyroidism, it does come with potential side effects and risks. Serious reactions include:

Allergic responses such as hives, itching or skin rash
Swelling of the face, lips, tongue or throat accompanied by difficulty breathing
Fever and swollen glands that may indicate infection
Unusual bruising or bleeding due to decreased platelets in the blood
Extreme fatigue which can be a sign of low red blood cells (anemia)
Abnormal heart rhythms leading to palpitations or chest pain
Neurological issues including headaches, dizziness and numbness

Contraindications for Ptu and Methimazole?

Both PTU and Methimazole, like most other antithyroid medications, can cause changes in mood or behavior in some people. If you notice an increase in irritability, nervousness, depression or any abnormal thoughts and behaviors while taking these drugs, please consult your healthcare provider immediately.

Neither PTU nor Methimazole should be taken if you are using or have recently used iodine supplements or radiopharmaceutical agents that contain iodine. Inform your physician about all the medicines you are currently taking; there needs to be a sufficient gap between the usage of iodine-containing substances and starting with antithyroid medications like PTU and Methimazole to prevent dangerous interactions.

Moreover, both medications require regular liver function monitoring due to potential hepatotoxicity. Therefore it's crucial for patients on either medication to watch for symptoms such as jaundice (yellowing of skin/eyes), severe fatigue, dark urine or abdominal pain which may signify liver damage.

How much do Ptu and Methimazole cost?

For the brand name versions of these drugs:

The price for 60 tablets of Propylthiouracil (PTU, 50 mg) averages around $150-$200, which works out to about $2.50-$3.30/day based on a typical dose.
The cost for 30 tablets of Methimazole (10 mg) is approximately $70-$90, or roughly $2.33-$3 per day.

Thus, if you are taking higher doses of PTU (for example above 300 mg/day), then Methimazole could be less expensive on a per-day treatment basis. It's important to note that costs should not dictate your choice between these two medications; efficacy and side effect profiles are paramount considerations.

When considering generic versions:

Generic PTU is available in packs starting from 30 tablets with approximate costs varying widely depending on location and insurance coverage but generally lower than the branded version.
Generic Methimazole also comes in various pack sizes with prices likewise dependent on factors like location and coverage but typically cheaper than their branded counterpart.

Always consult your healthcare provider when deciding between these two medications as they have different indications and side effect profiles despite both being used for hyperthyroidism management.

Popularity of Ptu and Methimazole

Propylthiouracil (PTU) and Methimazole are antithyroid agents primarily used in the treatment of hyperthyroidism caused by Grave's disease.

Methimazole is the more commonly prescribed medication in the United States, with approximately 1.2 million prescriptions filled annually as of 2020. It accounts for roughly 75% of all antithyroid drug prescriptions across the country. Its popularity can be attributed to its once-daily dosage regimen and lower incidence of severe side effects when compared to PTU.

On the other hand, Propylthiouracil was prescribed about 400,000 times in the same year, making up nearly a quarter of all antithyroid medications dispensed. The use of PTU has been on a gradual decline since mid-2009 due to concerns over potential severe liver injury associated with its use, particularly during first trimester pregnancy or when patients cannot tolerate methimazole.

Conclusion

Both Propylthiouracil (PTU) and Methimazole have been used for many years in the management of hyperthyroidism, with numerous clinical studies confirming their effectiveness. These two drugs work by inhibiting the production of thyroid hormones, but they do so through slightly different mechanisms, hence they may be prescribed under varying circumstances. PTU is often used as a first-line treatment option during pregnancy due to its lower propensity to cross the placenta. However, outside of pregnancy or breastfeeding situations, methimazole is usually preferred due to less frequent dosing and lower risk of severe side effects.

Both medications are accessible in generic form which can provide significant cost savings especially for out-of-pocket expenses. It's important to note that both PTU and Methimazole typically require an adjustment period where symptoms may persist until adequate control of thyroid hormone levels is achieved.

The adverse effect profile between these two drugs varies somewhat; although both are generally well-tolerated, PTU has more potential for serious side effects such as liver damage compared to methimazole. For individuals on either drug regimen, regular monitoring of thyroid function tests and lookout for any signs suggestive of liver injury or other adverse reactions like rash or joint pain should prompt immediate medical attention.

Refrences

Moriyama, K., Tagami, T., Usui, T., Naruse, M., Nambu, T., Hataya, Y., … Nakao, K. (2007, March 1). Antithyroid Drugs Inhibit Thyroid Hormone Receptor-Mediated Transcription. The Journal of Clinical Endocrinology & Metabolism. The Endocrine Society.http://doi.org/10.1210/jc.2006-1621
Hoffman, W. H., & Miceli, J. N. (1988). Pharmacokinetics of Propylthiouracil in Children and Adolescents with Graves’ Disease in the Hyperthyroid and Euthyroid States. Developmental Pharmacology and Therapeutics. S. Karger AG.http://doi.org/10.1159/000457669
Saberi, M., Sterling, F. H., & Utiger, R. D. (1975, February 1). Reduction in extrathyroidal triiodothyronine production by propylthiouracil in man. Journal of Clinical Investigation. American Society for Clinical Investigation.http://doi.org/10.1172/jci107924
Heinen, E., Herrmann, J., Mosny, D., Moreno, F., Teschke, R., & Krüskemper, H. L. (1981, July). Inhibition of peripheral deiodination of 3,5,3′-triiodothyronine: an adverse effect of propylthiouracil in the treatment of T3-thyrotoxicosis. Journal of Endocrinological Investigation. Springer Science and Business Media LLC.http://doi.org/10.1007/bf03349453
Chattaway, J. M., & Klepser, T. B. (2007, June). Propylthiouracil Versus Methimazole in Treatment of Graves' Disease During Pregnancy. Annals of Pharmacotherapy. SAGE Publications.http://doi.org/10.1345/aph.1h535
Lee, S. Y., & Pearce, E. N. (2023, October 17). Hyperthyroidism. Jama. American Medical Association (AMA).http://doi.org/10.1001/jama.2023.19052
Tan, S., Chen, L., Jin, L., & Fu, X. (2021, July 30). The efficiency and safety of methimazole and propylthiouracil in hyperthyroidism. Medicine. Ovid Technologies (Wolters Kluwer Health).http://doi.org/10.1097/md.0000000000026707
He, C., Hsieh, A., Pei, D., Hung, Y., Wu, L., Yang, T., … Kuo, S. (2004, May 18). Comparison of single daily dose of methimazole and propylthiouracil in the treatment of Graves’ hyperthyroidism. Clinical Endocrinology. Wiley.http://doi.org/10.1111/j.1365-2265.2004.02032.x
Emiliano, A. B., Governale, L., Parks, M., & Cooper, D. S. (2010, May 1). Shifts in Propylthiouracil and Methimazole Prescribing Practices: Antithyroid Drug Use in the United States from 1991 to 2008. The Journal of Clinical Endocrinology & Metabolism. The Endocrine Society.http://doi.org/10.1210/jc.2009-2752