Assessment of interchangeability of two brands of levothyroxine preparations with a third-generation TSH assay

Escalante, David A.; Arem, Noura; Arem, Ridha

doi:10.1016/s0002-9343(99)80316-7

Cited by 29Thyroid Disorders and TreatmentsThyroid and Parathyroid SurgeryClinical Laboratory Practices and Quality Control

Assessment of interchangeability of two brands of levothyroxine preparations with a third-generation TSH assay

Escalante, David A., Arem, Noura, Arem, Ridha·1995·The American Journal of Medicine

DOI 10.1016/s0002-9343(99)80316-7

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Abstract

Purpose To evaluate, in a prospective fashion, the clinical interchangeability between two brands of levothyroxine, Synthroid (Boots Pharmaceuticals, Inc., Lincolnshire, Illinois) and Levoxine (Daniels Pharmaceuticals, Inc., St. Petersburg, Florida), by using clinical scores of hyperthyroidism and hypothyroidism, free thyroxine index (FTI), sensitive thyroid-stimulating hormone (TSH), and thyrotropin-releasing hormone (TRH) stimulation testing.Patients and methods Twenty-three of the 31 patients with long-standing primary hypothyroidism (6 men, 25 women; age range 30 to 71 years, mean 47.2 +/- 2.2 SEM) were switched from Synthroid to Levoxine (group 1) and the remaining patients from Levoxine to Synthroid (group 2). After switching, each patient continued to receive the same dosage as previously. Clinical scores of hypothyroidism and hyperthyroidism (Billewicz and Crooks scoring systems, respectively), basal FTI, and TRH stimulation test were obtained before and 4 months after the switching. Comparison of the variables before and after switching was performed separately in each subgroup and in the entire group.Results There was no statistically significant difference in the hypothyroid clinical scores (-40.1 +/- 1.2 versus -39.7 +/- 1.2), the hyperthyroid clinical scores (-19.6 +/- 0.9 versus -19.2 +/- 1.0), FTI (9.6 +/- 0.3 versus 9.6 +/- 0.3), basal TSH levels (1.4 +/- 0.2 versus 1.4 +/- 0.2 mIU/L), or the magnitude of TSH response to TRH (mean delta TSH 9.4 +/- 1.5 versus 9.2 +/- 1.4 mIU/L), whether the patients were receiving Synthroid or Levoxine.Conclusions Switching did not result in substantial clinical or laboratory changes in any individual patient. We conclude that the two brands of levothyroxine are clinically interchangeable.

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Escalante et al. found two popular LT4 brands to be bioequivalent and therapeutically equivalent.
“Escalante et al. (99) studied two well-known, popular brands of LT4 (one of which has been reformulated twice since this evaluation) and found them to be both bioequivalent and therapeutically equivalent.”
From Guidelines for the Treatment of Hypothyroidism: Prepared by the American Thyroid Association Task Force on Thyroid Hormone Replacement (2014) · cites this paper as [99]

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Authors: Escalante, D. A., Arem, N., & Arem, R.
Affiliations: Baylor College of Medicine (US)
Corresponding author: Arem, Ridha
Venue: The American Journal of Medicine
Publisher: Elsevier BV
Published: 1995-04
Volume: 98
Issue: 4
Pages: 374-378
ISSN: 0002-9343 (ISSN-L)
DOI: 10.1016/s0002-9343(99)80316-7
OpenAlex: W2110287465
Cited by: 29
References: 26
Citations by year: 2021: 2 · 2019: 1 · 2016: 1 · 2015: 1 · 2014: 2 · 2012: 2
FWCI: 3.16
Type: journal article
Language: en
Open access: closed
Licence: www.elsevier.com/tdm/userlicense/1.0/ (tdm)
www.elsevier.com/legal/tdmrep-license (tdm)
Locations: The American Journal of Medicine (publishedVersion)
PubMed (publishedVersion)
Topics: Health Sciences › Medicine › Endocrinology, Diabetes and Metabolism › Thyroid Disorders and Treatments
Health Sciences › Medicine › Surgery › Thyroid and Parathyroid Surgery
Health Sciences › Medicine › Physiology › Clinical Laboratory Practices and Quality Control
Keywords: levothyroxine, drug interchangeability, brand switching, primary hypothyroidism, free thyroxine index, thyroid-stimulating hormone, TRH stimulation test
MeSH terms: Adult, Aged, Female, Humans, Hypothyroidism, Male, Middle Aged, Thyroid Function Tests, Thyrotropin, Thyroxine

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Assessment of interchangeability of two brands of levothyroxine preparations with a third-generation TSH assay

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