• Karunrat Tewthanom Department of Pharmacy, Faculty of Pharmacy, Silpakorn University, Nakhon Pathom, 73000, Thailand
  • Walaya Jongjaroenprasert Department of Medicine, Faculty of Medicine, Ramathibodi hospital, Mahidol University, Bangkok, 10400, Thailand


Objective: Hypothyroid has still be a problem in Thailand. Lack of pharmacokinetics information of levothyroxine in athyreotic patients for modify dosing. Therefore, the aim of this study was to investigate the pharmacokinetic parameters of 2 doses of levothyroxine(50 mg and 100 mg) in such group of patients.

Methods: The 24 athyreotic patients were recruited and randomly assigned to receive 50 mg or 100 mg of levothyroxine. The pharmacokinetic parameters (Cmax, Tmax, AUC0-8, ke, T1/2 and Vd) of FT4 and TSH were calculated by the non-compartment model. The parameters of 2 doses were compared.

Results: From the results found that, by monitoring FT4, there was no statistically significant difference (p>0.05) of almost all pharmacokinetic parameters between 2 doses except Cmax which has significant greater in 100 mg of levothyroxine. While all pharmacokinetics parameters of TSH were not statistically significant difference. The use of non-compartment model seems appropriate for calculation of pharmacokinetic parameters of FT4 (R2 = 0.81) while it has poor predictive capacity in terms of TSH (R2 = 0.24).

Conclusion: In conclusion, administration of 50 mg and 100 mg of levothyroxine to athyreotic patients have similar pharmacokinetic in term of FT4(non-significant different in Tmax, AUC) and TSH. Further study of these parameters in more subjects is needed.

Keywords: Pharmacokinetics, Athyreotic patients, Levothyroxine


1. Hollowell JG, Staehling NW, Flanders WD, Hannon WH, Gunter EW, CA S. Serum TSH, T, and thyroid antibodies in the united states population (1988 to 1994): National Health and Nutrition Examination Survey (NHANES III). J Clin Endocrinol Metab 2002;87:489-99.
2. Vanderpump MP, Tunbridge WM, French JM, Appleton D, Bates DFC. The incidence of thyroid disorders in the community: a twenty-year follow-up of the whickham survey. Clin Endocrinol (Oxf) 1995;43:55-68.
3. Tunbridge WM, Evered DC, Hall R, Appleton D, Brewis M, Clark F. The spectrum of thyroid disease in a community: the Whickham survey. Clin Endocrinol (Oxf) 1977;7:481-93.
4. AACE Thyroid Task Force. American association of clinical endocrinologist medical guidelines for clinical practice for evaluation and treatment of hyperthyroidism and hypothyroidism. Endocrine Practice 2002;8:457-69.
5. Thyroid Carcinoma Task Force. AACE/AAES medical/surgical guidelines for clinical practice: management of thyroid carcinoma. Endocrine Practice 2001;7:213-20.
6. Annemieke Roos, Suzanne P Linn-Rasker, Ron T van Domburg, Jan P Tijssen, Arie Berghout. The starting dose of levothyroxine in primary hypothyroidism treatment. A prospective, randomised, double-blind trial. Arch Intern Med 2005;165:1714-20.
7. Srinivas V, Oyibo SO. Levothyroxine pseudo malabsorption and thyroxine absorption testing with use of high-dose levothyroxine: case report and discussion. Endocr Pract 2010;16:1012-5.
8. Blakesley V, Awni W, Locke C, Ludden T, Granneman GR, Braverman LE. Are bioequivalence studies of levothyroxine sodium formulations in euthyroid volunteers reliable? Thyroid 2004;14:191-200.
9. Eduardo Abib Junior, J osé Pedrazzoli Junior, lf duarte, Ps marques, DP tosetti, Sf souza, et al. Levothyroxine bioequivalence study: determination in healthy volunteers by microparticle enzyme immunoassay. Global J Med Res 2010;10:58-63.
10. Soldin OP, Soldin SJ, Vinks AA, Younis I, Landy HJ. Longitudinal comparison of thyroxine pharmacokinetics between pregnant and nonpregnant women: a stable-isotope study. Ther Drug Monit 2010;32:767-73.
11. Jari J Lilja, Kalevi Laitinen, Neuvonen PJ. Effects of grapefruit juice on the absorption of levothyroxine. Br J Clin Pharmacol 2005;60:337-41.
128 Views | 337 Downloads
How to Cite
Tewthanom, K., & Jongjaroenprasert, W. (2016). THE PHARMACOKINETICS OF 2 DOSES (50 µG AND 100 µG) LEVOTHYROXINE TREATMENT IN ATHYREOTIC PATIENTS. International Journal of Applied Pharmaceutics, 8(4), 66-68. Retrieved from
Original Article(s)