Cited by 76Thyroid Disorders and TreatmentsPharmacogenetics and Drug MetabolismEstrogen and related hormone effects

Raloxifene Causing Malabsorption of Levothyroxine

Siraj, Elias S., Gupta, Manjula K., Reddy, S. Sethu K.·2003·Archives of Internal Medicine

Abstract

To our knowledge, raloxifene hydrochloride, a selective estrogen receptor modulator, has never been reported to interfere with absorption of levothyroxine. We describe a 79-year-old woman with chronic, treated primary hypothyroidism, presenting with increasing levothyroxine requirement while taking raloxifene at the same time as levothyroxine. For two 6- to 8-week periods, we separated the ingestion of raloxifene and levothyroxine by about 12 hours. In addition, we tested the absorption of 1.0 mg of levothyroxine sodium with and without the coadministration of 60 mg of raloxifene hydrochloride on 2 separate occasions by collecting serial blood samples for 6 hours. Hypothyroidism occurred in a reproducible fashion whenever levothyroxine and raloxifene were administered together and improved whenever they were taken separately. Combined administration of levothyroxine and raloxifene resulted in lower levels of serum thyroxine compared with administration of levothyroxine alone. By a yet unknown mechanism, raloxifene caused malabsorption of levothyroxine in our patient when coadministered.

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Crossref · 10.1001/archinte.163.11.1367

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Authors
Siraj, E. S., Gupta, M. K., & Reddy, S. S. K.
Affiliations
Cleveland Clinic (US)
Venue
Archives of Internal Medicine
Published
2003-06-09
Volume
163
Issue
11
Pages
1367
ISSN
0003-9926 (ISSN-L)
OpenAlex
W1975298909
Cited by
76
References
23
Citations by year
2025: 1 · 2023: 2 · 2022: 2 · 2021: 2 · 2019: 2 · 2018: 3 · 2017: 3 · 2016: 3 · 2015: 7 · 2014: 5 · 2013: 3 · 2012: 3
FWCI
2.85
Type
journal article
Language
en
Open access
closed
Locations
  • Archives of Internal Medicine (publishedVersion)
  • PubMed (publishedVersion)
Topics
  • Health Sciences › Medicine › Endocrinology, Diabetes and Metabolism › Thyroid Disorders and Treatments
  • Life Sciences › Pharmacology, Toxicology and Pharmaceutics › Pharmacology › Pharmacogenetics and Drug Metabolism
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Genetics › Estrogen and related hormone effects
Keywords
raloxifene, levothyroxine, drug-drug interactions, malabsorption, selective estrogen receptor modulators, primary hypothyroidism, thyroid hormone absorption
MeSH terms
Absorption, Aged, Drug Interactions, Female, Humans, Hypothyroidism, Thyroxine, Selective Estrogen Receptor Modulators, Raloxifene Hydrochloride

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