Dosages
Side effects in children
Warnings & precautions in children
Contra-indications in children

Interactions
PK
Renal impairment
References

Thiamazole

Generic name
Thiamazole
Brand name
ATC Code
H03BB02

Pharmacokinetics in children

Age Dose Cmax Tmax [h] Vd apparent [L/kg] T1/2[h] Reference
2-15 years (n=9) 20 mg/m2 9,2 (4,4-12,6) μmol/L* 1,0 (0,5-4)* 0,602 (0,516-0,913)* 4,75 (2,73-6,04)* Okuno 1987; PAR 2011
Adults 9 mg 150 ng/mL 0,4-1,2 - 3 SmPC Methizol

*median (range)

The thyreostatic effect of thiamazole lasts for approximately 24 hours. This is due to the fact that the substance is actively absorbed into the thyroid and that the inhibition of hormone production apparently correlates with the intrathyroidal rather than the serum concentration. [SmPC Thiamazol Henning®]

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dose recommendation of formulary compared to licensed use (on-label versus off-label)

No information is present at this moment.

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Available formulations

No information is present at this moment.

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Dosages

Hyperthyroidism
  • Oral
    • 1 month up to 18 years
      • 0.5 mg/kg/day in 2 - 3 doses. Max: 40 mg/day.

      • Titrate based on effect. 

    • Preterm and Term neonate
      • 0.5 mg/kg/day in 2 - 3 doses.

      • Titrate based on effect. 

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Renal impaiment in children > 3 months

GFR ≥10 ml/min/1.73m2: Dose adjustment not required.

GFR <10 ml/min/1.73m2: A general recommendation on dose adjustment cannot be provided.

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The complete list of all undesirable drug reactions can be found in the national Summary of Product Characteristics (SmPC) – click here

Side effects in children

Side effects mainly occur in the first 3 months of therapy with a higher rate in younger children. [Mooij et al. 2022] 

Observed side effects in children are as follows: pruritus, arthralgia, muscle pain and/or joint pain, lymphopenia, eosinophilia, neutropenia, mild liver injury [Rivkees et al. 2010]. Agranulocytosis is reported very rarely in pediatric patients. [Mooij et al. 2022] 

Severe skin hypersensitivity reactions, such as generalized dermatitis including Stevens-Johnson syndrome, have been reported very rarely in children and adolescents. [SmPC Methizol]

The side effects are dose-dependent [Lee et al. 2021]

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The complete list of all contra-indications can be found in the national Summary of Product Characteristics (SmPC) – click here

Contra-indications

No information available on specific contra indications in children.

The complete list of all warnings and precautions can be found in the national Summary of Product Characteristics (SmPC) – click here

Warnings & precautions in children

If pruritus / rash is moderate, antihistamines can be administered. Dose reduction or stop of therapy in case of severe allergic reactions.  Switching to propylthiouracil is not recommended. [Mooij et al. 2022]

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Interactions

The complete list of all interactions can be found in the national Summary of Product Characteristics (SmPC) – click here

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Thiouracils
H03BA02
Sulfur-containing imidazole derivatives
H03BB01

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References

  1. Merck Healthcare Germany GmbH., SmPC Thyrozol® 5/10/20 mg Filmtabletten (13478.00-02), 02/2022
  2. Noordam C et al, Werkboek Kinderendocrinologie, digitale publicatie op www.nvk.nl (alleen leden), 2010
  3. Teva Nederland BV., DHPC Carbizol-Thiamazol 31-01-2019
  4. Aspen Pharma Trading Limited., SmPC Strumazol (RVG 02224) 15-02-2019, www.geneesmiddeleninformatiebank.nl
  5. Minamitani, K, et al, Guidelines for the treatment of childhood-onset Graves’ disease in Japan, 2016, Clin Pediatr Endocrinol, 2017, 26(2), 29-62
  6. Kahaly, GJ, et al, European Thyroid Association Guideline for the Management of Graves’ Hyperthyroidism, Eur Thyroid J, 2018, 7, 167–186
  7. Fine S, et al., Neonatal Graves disease with persistent hypoglycemia: A case report., SAGE Open Med Case Rep, 2024, 12, 2050313X241237433
  8. Merck Sharp & Dohme B.V., Public Assessment Report for paediatric studies submitted in accordance with Article 45 of Regulation (EC) No1901/2006., 2011
  9. Mooij CF, et al., European Thyroid Association Guideline for the management of pediatric Graves' disease., Eur Thyroid J, 2022, 11(1), e210073
  10. mibe GmbH Arzneimittel., SmPC Methizol SD 5 mg/- 20 mg (3000158.00.00/49499.00.00), 01/2019
  11. Rivkees SA, et al., Adverse events associated with methimazole therapy of graves' disease in children, Int J Pediatr Endocrinol., 2010, 176970
  12. Segni M, et al., Special features of Graves' disease in early childhood, Thyroid, 1999, 9(9), 871-7
  13. Kayas L, et al., TSHRV656F Activating Variant of the Thyroid Stimulating Hormone Receptor Gene in Neonatal Onset Hyperthyroidism: A Case Review., J Clin Res Pediatr Endocrinol, 2022, 14(1), 114-8
  14. Okuno A, et al., Pharmacokinetics of methimazole in children and adolescents with Graves' disease. Studies on plasma and intrathyroidal concentrations., Acta Endocrinol (Copenh), 1987, 115(1), 112-8
  15. Lee HG, et al., Efficacy and adverse events related to the initial dose of methimazole in children and adolescents with Graves' disease., Ann Pediatr Endocrinol Metab., 2021, 26(3), 199-204
  16. Zhu L, et al., The tortuous diagnosis of one case of neonatal hyperthyroidism., BMC Pediatr., 2024, 24(1), 43
  17. Taha D, et al., Familial neonatal nonautoimmune hyperthyroidism due to a gain-of-function (D619G) thyrotropin-receptor mutation, J Pediatr Endocr Met, 2021, 34(2), 267-71
  18. Yasuda K, et al., Relationship between dose of antithyroid drugs and adverse events in pediatric patients with Graves' disease., Clin Pediatr Endocri., 2017, 26(1), 1-7
  19. Aspen Pharma Trading Limited., SmPC Strumazol (RVG 02224) 02-01-2025, www.geneesmiddeleninformatiebank.nl

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Changes

Changes