The Effect of Famotidine, Esomeprazole, and Ezetimibe on Levothyroxine Absorption
Abstract
BACKGROUND: Recent literature describing the effect of gastric acid suppression on levothyroxine absorption has been inconsistent. Also, ezetimibe, a lipid-lowering compound that inhibits intestinal absorption of cholesterol, may interfere with levothyroxine absorption. The objective of this study was to measure changes in levothyroxine absorption before and after famotidine, esomeprazole or single-dose ezetimibe." METHODS: We conducted levothyroxine absorption testing on 30 healthy volunteers, excluding those with thyroid disease. Subjects were randomized to receive one of three regimens: 1 week of either famotidine or esomeprazole, or a single dose of ezetimibe administered simultaneously with levothyroxine (n = 10 in each group). Baseline levothyroxine absorption testing was performed on all subjects using 600 mcg of Synthroid with thyroid hormone levels checked at 0, 2, 4, 6, and 8 hours after administration, and then repeated 6 weeks later, after administration of one of the three study drug regimens. The area under the curve (AUC) over 8 hours for serum thyroxine (T4), triiodothyronine (T3), and free T4 index, and the mean peak hormone levels achieved during levothyroxine absorption testing at baseline and following administration of one of the three study medications were compared using paired t-tests. RESULTS: Peak mean hormone levels and AUCs of T4, T3, and free T4 index during absorption testing before and after each of three study medications did not differ. Results for differences before and after study medication did not reach significance even when using the subtractive correction method of AUC calculation. CONCLUSIONS: No differences were noted in levothyroxine absorption after gastric acid suppression with 1 week of famotidine or esomeprazole. A simultaneously administered dose of ezetimibe did not significantly change levothyroxine absorption.
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LT4 absorption was unaltered with use of PPIs (146,147) and histamine-2 blockers (147) for a 1-week period in two other studies in healthy volunteers.
“LT4 absorption was unaltered with use of PPIs (146,147) and histamine-2 blockers (147) for a 1-week period in two other studies in healthy volunteers.”
From Guidelines for the Treatment of Hypothyroidism: Prepared by the American Thyroid Association Task Force on Thyroid Hormone Replacement (2014) · cites this paper as [147]
Clinical studies of one week pantoprazole, 3 months omeprazole, and one week esomeprazole did not find significant intergroup differences in TSH or thyroid hormone levels.
“In contrast, various clinical studies of one week of treatment with pantoprazole [ 74 ], 3 months of treatment with omeprazole [ 75 ], and a week’s treatment with esomeprazole [ 76 ] did not find significant intergroup differences in the TSH or thyroid hormone levels.”
From Factors influencing the levothyroxine dose in the hormone replacement therapy of primary hypothyroidism in adults (2022) · cites this paper as [76]
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- Authors
- Ananthakrishnan, S., Braverman, L. E., Levin, R. M., Magnani, B., & Pearce, E. N.
- Affiliations
- Boston University (US)
- Tufts Medical Center (US)
- Venue
- Thyroid
- Publisher
- SAGE Publications
- Published
- 2008-05
- Volume
- 18
- Issue
- 5
- Pages
- 493-498
- ISSN
- 1050-7256 (ISSN-L)
- 1557-9077
- OpenAlex
- W1981406776
- Cited by
- 38
- References
- 26
- Citations by year
- 2026: 1 · 2025: 1 · 2024: 2 · 2023: 4 · 2021: 5 · 2020: 1 · 2019: 1 · 2018: 2 · 2017: 3 · 2016: 2 · 2015: 3 · 2014: 6 · 2012: 2
- FWCI
- 1.21
- Type
- journal article
- Language
- en
- Open access
- closed
- Locations
- Thyroid (publishedVersion)
- PubMed (publishedVersion)
- Funders
- National Institute of Diabetes and Digestive and Kidney Diseases (5K23DK4611)
- National Center for Research Resources (M01-RR-00533, M01RR000533)
- 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 › Pharmacology, Toxicology and Pharmaceutics › Pharmaceutical Science › Drug Solubulity and Delivery Systems
- Keywords
- famotidine, esomeprazole, ezetimibe, gastric acid suppression, drug-drug interactions, triiodothyronine, free thyroxine index, cholesterol absorption inhibition
- MeSH terms
- Ezetimibe, Adult, Anti-Ulcer Agents, Anticholesteremic Agents, Azetidines, Dose-Response Relationship, Drug, Female, Humans, Intestinal Absorption, Male, Random Allocation, Thyroxine, Triiodothyronine, Famotidine, Esomeprazole
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