Name: China Manufacturer Supply Top Purity Methylthiouracil CAS 56-04-2 with good service
Brand: Wuhan Fortuna Chemical Co., Ltd.

Specifications of Methylthiouracil CAS 56-04-2

Item	Specifications	Results
Appearance	Almost white or yellowish crystalline powder	Conform
Loss on drying	≤0.5%	0.15%
Sulphated ash	≤0.1%	0.08%
Assay	≥99.0%	99.26%

Parameters of Methylthiouracil CAS 56-04-2

Product parameters
Cas number:	56-04-2
Appearance:	Almost white or yellowish crystalline powder
Purity:	99% min
Package details:	1kg/foil bag, 25kg/drum
Brand:	Fortunachem

Methylthiouracil is a thiourea-derived antithyroid drug. It belongs to the same class as the more commonly used propylthiouracil (PTU) and methimazole.

Chemical Nature: It is a thiouracil derivative, meaning it contains a thiourea moiety within a uracil (a pyrimidine) base structure.
Primary Action: It works by inhibiting the synthesis of thyroid hormones (thyroxine/T4 and triiodothyronine/T3) in the thyroid gland.

Mechanism of Action

Its therapeutic effect comes from two key actions:

Inhibition of Thyroid Peroxidase: It blocks the enzyme thyroid peroxidase, which is essential for incorporating iodine into tyrosine residues on thyroglobulin—a critical step in thyroid hormone production.
Inhibition of Conversion (Mild): Like PTU, it has a secondary effect of partially inhibiting the conversion of the less active T4 to the more active T3 in peripheral tissues, though this effect is weaker than its synthesis blockade.

Historical and Medical Uses

Primary Use: Treatment of Hyperthyroidism

Methylthiouracil was used to manage conditions where the thyroid gland is overactive, such as:

Graves' Disease: The most common cause of hyperthyroidism.
Toxic Nodular Goiter.
Preparation for Thyroid Surgery or Radioactive Iodine Therapy: To make a patient "euthyroid" (normal thyroid state) before a definitive procedure.

Current Status: Largely Obsolete

Methylthiouracil is rarely, if ever, used in modern human medicine. It has been almost entirely replaced by other antithyroid drugs for several critical reasons:

Higher Toxicity: It is associated with a significantly higher incidence of serious adverse effects, particularly:

Agranulocytosis: A severe, life-threatening drop in white blood cells (neutrophils) that increases the risk of serious infections.
Hepatotoxicity: Liver damage.
Vasculitis: Inflammation of blood vessels.

Better Alternatives Available:

Methimazole (MMI): Now the first-line drug for hyperthyroidism in most cases (except during the first trimester of pregnancy). It is more potent, has a longer half-life (allowing once-daily dosing), and has a better safety profile.
Propylthiouracil (PTU): Used in specific situations, such as during the first trimester of pregnancy (due to methimazole's teratogenic risk) or in thyroid storm (because of its stronger inhibition of T4 to T3 conversion). PTU also carries risks of agranulocytosis and hepatotoxicity but is generally preferred over methylthiouracil when needed.

Why is it Still Mentioned?

Historical Context: It is an important part of the history of endocrinology and the development of antithyroid therapies.
Veterinary Medicine: It may have historical or very niche use in veterinary practice for treating hyperthyroidism in animals, though safer options are preferred there as well.
Research Chemical: It may be used in laboratory research to experimentally induce hypothyroidism or study thyroid hormone pathways.

Key Side Effects & Warnings

(These are cited as reasons for its obsolescence)

Agranulocytosis: The most dangerous risk.
Hepatitis and Liver Failure.
Skin Rashes, Urticaria (hives), and Arthralgia (joint pain).
Drug Fever.
Vasculitis.

Conclusion

In summary, Methylthiouracil is an obsolete antithyroid medication that was once used to treat hyperthyroidism. Due to its unfavorable safety profile, particularly a high risk of agranulocytosis and hepatotoxicity, it has been superseded by safer and more effective drugs like Methimazole and Propylthiouracil. You will find it in medical history books and pharmacological texts, but it is no longer a standard part of the therapeutic arsenal for thyroid disease.