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Cited by 22Thyroid Disorders and TreatmentsAnalytical Methods in PharmaceuticalsDrug Solubulity and Delivery Systems

A Study in Normal Human Volunteers to Compare the Rate and Extent of Levothyroxine Absorption from Synthroid® and Levoxine®

Berg, Jeffrey A., Mayor, Gilbert H.·1992·The Journal of Clinical Pharmacology
DOI 10.1177/009127009203201213
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Abstract

Numerous branded and generic formulations of levothyroxine (LT4) sodium tablets are currently available. Results from previous studies attempting to examine the comparative bioavailability of these formulations are difficult to interpret because of subject heterogeneity, single time-point blood sampling, varying degrees of hypothyroidism, and other factors. This study was devised to compare the rate and extent of absorption of LT4 from different LT4 sodium tablet formulations, in a simple model using a single-dose two-way single-blind, randomized cross-over design in 30 normal, healthy, nonpregnant, female subjects. This design controlled for many factors that limited previous LT4 bioavailability studies. Subjects were given a single 600 micrograms dose of LT4 as either Synthroid (Boots Pharmaceuticals, Inc., Lincolnshire, IL) tablets (formulation A) or Levoxine tablets (Daniels Pharmaceuticals, St. Petersburg, FL; formulation B). Measurements of baseline-corrected total T4 serum concentrations determined at multiple time points demonstrated statistically significant differences between the two formulations at the 1.00, 3.00, 5.00, and 18.00 hour sampling times. Statistically significant differences for area under the curve (AUC) (0 to 48 hours) (formulation A, 159.9 +/- 9.4 micrograms-hour/dL; formulation B, 193.4 +/- 10.1 micrograms-hour/dL) and maximum peak plasma concentration (Cmax) (formulation A, 5.91 +/- .34; formulation B, 7.12 +/- .32) also were demonstrated. Furthermore, the ratio of the baseline-corrected total T4 concentrations (B/A x 100) were 120.9% for AUC and 120.5% for Cmax. These data demonstrate that the administration of Synthroid and Levoxine result in a significantly different rate and extent of absorption of LT4, and therefore these two formulations cannot be considered bioequivalent.(ABSTRACT TRUNCATED AT 250 WORDS)

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  • Changes in brands or formulations may cause TSH elevations, as supported by some reports.

    “Since it is almost impossible to conduct a direct comparative analysis of the bioavailability of all products, we cannot abandon the hypothesis that changes in brands or formulations cause TSH elevations, as supported by some reports (109–111).”

    From Levothyroxine: conventional and novel drug delivery formulations. (2023) · cites this paper as [109]

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Authors
Berg, J. A., & Mayor, G. H.
Corresponding author
Berg, Jeffrey A.
Venue
The Journal of Clinical Pharmacology
Publisher
Wiley
Published
1992-12
Volume
32
Issue
12
Pages
1135-1140
ISSN
  • 0021-9754 (ISSN-L)
  • 0091-2700
  • 1552-4604
DOI
10.1177/009127009203201213
OpenAlex
W4297107769
Cited by
22
References
10
Citations by year
2022: 2 · 2019: 1 · 2015: 1 · 2013: 2 · 2012: 3
FWCI
0.85
Type
journal article
Language
en
Open access
closed
Licence
onlinelibrary.wiley.com/termsAndConditions#vor (vor, 7402 d)
Locations
  • The Journal of Clinical Pharmacology (publishedVersion)
  • PubMed (publishedVersion)
  • PubMed
Topics
  • Health Sciences › Medicine › Endocrinology, Diabetes and Metabolism › Thyroid Disorders and Treatments
  • Physical Sciences › Chemistry › Analytical Chemistry › Analytical Methods in Pharmaceuticals
  • Life Sciences › Pharmacology, Toxicology and Pharmaceutics › Pharmaceutical Science › Drug Solubulity and Delivery Systems
Keywords
levothyroxine, bioequivalence, drug absorption, bioavailability, generic drug formulation, area under the curve, Cmax, healthy female volunteers
MeSH terms
Adult, Biological Availability, Female, Humans, Intestinal Absorption, Tablets, Thyroxine, Triiodothyronine, Single-Blind Method

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