Is Neo Mercazole a Steroid?
No, Neo Mercazole (carbimazole) is not a steroid—it is an antithyroid drug that inhibits thyroid hormone synthesis by blocking iodine organification in the thyroid gland. 1
Drug Classification and Mechanism
- Carbimazole belongs to the mercaptoimidazoline class of antithyroid drugs, which are chemically and pharmacologically distinct from corticosteroids 1
- The drug works by inhibiting iodine organification in the thyroid gland, thereby reducing thyroid hormone production and secretion 2
- Carbimazole is a prodrug that is completely converted to methimazole (the active form) during absorption, with bioavailability of 80-95% 1
Clinical Context Where Confusion May Arise
The evidence shows that carbimazole and steroids are mentioned together in certain clinical scenarios, but they serve completely different purposes:
- In immunotherapy-induced thyroid dysfunction, carbimazole is listed as a treatment option alongside steroids, but they are separate drug classes used for different indications—beta-blockers are first-line for symptomatic hyperthyroidism, while carbimazole is "rarely" required and steroids may be used for painful thyroiditis 3
- Guidelines specifically distinguish between carbimazole (for anti-TSH receptor antibody-positive cases) and prednisolone (for painful thyroiditis), demonstrating they are different therapeutic agents 3
Pharmacological Properties Confirming Non-Steroid Classification
- Carbimazole has a volume of distribution of approximately 40L and is virtually non-protein-bound, unlike steroids which typically have high protein binding 1
- The drug has a half-life of 3-5 hours with total clearance of about 200ml/minute, pharmacokinetic properties inconsistent with steroid medications 1
- Carbimazole concentrates specifically in the thyroid gland where it exerts its antithyroid effects, a mechanism completely different from steroid hormone receptor binding 1