ATC Group: H03B Antithyroid preparations

The World Health Organization's ATC classification organizes medical drugs based on therapeutic properties, chemical composition, and anatomy. It helps make essential medicines readily available globally and is widely used in the pharmaceutical industry.

Position of H03B in the ATC hierarchy

Level Code Title
1 H Systemic hormonal preparations, excl. Sex hormones and insulins
2 H03 Thyroid therapy
3 H03B Antithyroid preparations

Group H03B contents

Code Title
H03BA Thiouracils
H03BB Sulfur-containing imidazole derivatives
H03BC Perchlorates
H03BX Other antithyroid preparations

Active ingredients in H03B

Active Ingredient Description
Benzylthiouracil
Carbimazole

Carbimazole, a thionamide, is a pro-drug which undergoes rapid and virtually complete metabolism to the active metabolite, thiamazole, also known as methimazole. The method of action is believed to be inhibition of the organification of iodide and the coupling of iodothyronine residues which in turn suppress the synthesis of thyroid hormones.

Potassium perchlorate
Propylthiouracil

Propylthiouracil is an antithyroid drug that depresses the formation of thyroid hormone. This is effected by interference both with the incorporation of iodine into tyrosyl residues and the coupling of such residues to form iodothyronines. Propylthiouracil achieves these actions by the inhibition of the enzyme peroxidase.

Sodium perchlorate

Perchlorate competitively inhibits the thyroid’s iodine uptake mechanism, iodination and affects iodisation by flushing the thyroid of iodide that is accumulating but has not yet been incorporated into a thyroglobulin molecule. Re-utilisation of iodide released outside the thyroid during deiodination of thyroid hormone is also inhibited. The antithyroid effect is based on the occurrence of iodine depletion.

Thiamazole

Thiamazole inhibits dose-dependently the incorporation of iodine into tyrosine and thereby the neosynthesis of thyroid hormones. This property permits symptomatic therapy of hyperthyroidism regardless of its cause.

Related product monographs

Title Information Source Document Type  
IRENAT Oral drops Base de donnรฉes publique des mรฉdicaments (FR) MPI, EU: SmPC
NEOMERCAZOLE Tablet Health Products Regulatory Authority (IE) MPI, EU: SmPC
TAPAZOLE Tablet FDA, National Drug Code (US) MPI, US: SPL/Old