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Open accessJournal ArticleDOI: 10.3390/PH14030206

Levothyroxine Interactions with Food and Dietary Supplements-A Systematic Review.

02 Mar 2021-Pharmaceuticals, policy and law (Multidisciplinary Digital Publishing Institute)-Vol. 14, Iss: 3, pp 206
Abstract: Levothyroxine (l-thyroxine, l-T4) is a drug of choice for treating congenital and primary hypothyroidism. Although clinically significant interactions between l-T4 and food can alter the safety and efficacy of the treatment, they still seem to be generally underestimated by patients, physicians and pharmacists. This review aimed to investigate the effects of meals, beverages, and dietary supplements consumption on l-T4 pharmacokinetics and pharmacodynamics, to identify the most evident interactions, and to perform the recommendations for safe co-administering of l-T4 and food. A total of 121 studies were identified following a systematic literature search adhering to PRISMA guidelines. After full-text evaluation, 63 studies were included. The results proved that l-T4 ingestion in the morning and at bedtime are equally effective, and also that the co-administration of l-T4 with food depends on the drug formulation. We found limited evidence for l-T4 interactions with coffee, soy products, fiber, calcium or iron supplements, and enteral nutrition but interestingly they all resulted in decreased l-T4 absorption. The altered l-T4 efficacy when ingested with milk, juices, papaya, aluminium-containing preparations, and chromium supplements, as well as observed enhancement effect of vitamin C on l-T4 absorption, shall be further investigated in larger, well-designed studies. Novel formulations are likely to solve the problem of coffee, calcium and iron induced malabsorption of l-T4. Maintaining a proper time interval between l-T4 and food intake, especially for coffee and calcium, or iron supplements, provides another effective method of eliminating such interactions.

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Open accessJournal ArticleDOI: 10.3389/FENDO.2021.664839
Chae Won Chung1, Eun Young Mo2, Gyung Seo Jung1, Yoo Hyung Kim1  +7 moreInstitutions (4)
Abstract: Background Malabsorption of levothyroxine (LT4) is a common problem faced in clinical practice. It is usually solved, if there are no complexities including gastrointestinal absorption disorder, by taking medicines on an empty stomach and avoiding foods interfering with LT4. Herein we present a rare case of a patient exhibiting malabsorption of LT4 with decreased membranous expression of ileal transporters. Case The 22-Year-old female presented with sustained hypothyroid status despite medication of 7.8 μg/kg LT4. Medical history and LT4 absorption test (the absorption rate 8.4%) excluded pseudomalabsorption. No organic gastrointestinal disorder was found in the patient by blood chemistry, endoscopies, and abdominal computed tomography scan. The immunohistochemical analysis showed decreased membranous expression of LAT1 and LAT2 in distal ileum and ascending colon in the patient compared to 20 controls who have no thyroid disease. The expression of MCT8 in colon appeared at both nucleus and brush border in the patient, while it was limited to brush border in controls. The expression of other transporters was similar between the patient and controls. Conclusion The changes of the expression of LAT1 and LAT2 in this patient showing LT4 malabsorption might help to understand the role of intestinal transporters in the absorption of LT4 in humans. The functional relevance of the decrement of LAT1 and LAT2 in this patient remains to be elucidated.

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Topics: Gastrointestinal disorder (57%), Malabsorption (55%), Thyroid disease (51%) ... read more

1 Citations


Open accessJournal ArticleDOI: 10.3390/FOODS10040720
29 Mar 2021-Foods
Abstract: Bisphosphonates and selective estrogen receptor modulators (SERMs) represent the two most important groups of medications taken orally and employed in osteoporosis treatment. Effectiveness of the therapy may be affected by poor patient adherence, in particular, due to the inconvenient dosing regimen of oral bisphosphonates. With this review we aimed to assess the effects that food, beverages, and dietary supplements consumed during treatment, along with the dosing regimens, may have on pharmacokinetics and pharmacodynamics of oral drugs employed in treating osteoporosis; we also aimed to shape the recommendations valuable for professional patients' counseling and education, to provide appropriate dosing regimens in order to improve adherence to the therapy. Food, beverages such as coffee, juices, and mineral water, as well as dietary supplements containing multivalent cations, e.g., calcium, magnesium, aluminium, iron, showed to have a deleterious effect on the bioavailability of all the investigated oral bisphosphonates, specifically alendronate, risedronate, ibandronate, minodronate, and etidronate. For risedronate, a delayed-release (DR) tablet was designed to solve the malabsorption problem in the presence of food, hence DR risedronate can be ingested following breakfast. For other oral bisphosphonates, the proper interval between drug and food, beverages, and dietary supplements intake should be maintained to minimize the risk of interactions. The effect of food on pharmacokinetic parameters of selective estrogen receptor modulators (SERMs) was found to be clinically irrelevant.

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Topics: Dosing (51%)

1 Citations




Journal ArticleDOI: 10.1210/ENDREV/BNAB031
Jacqueline Jonklaas1Institutions (1)
20 Sep 2021-Endocrine Reviews
Abstract: Hypothyroidism is a common endocrinopathy and levothyroxine is frequently prescribed. Despite the basic tenets of initiating and adjusting levothyroxine being agreed upon, there are many nuances and complexities to consistently maintaining euthyroidism. Understanding the impact of patient weight and residual thyroid function on initial levothyroxine dosage and consideration of age, co-morbidities, TSH goal, life stage, and quality of life as levothyroxine is adjusted can be challenging and continually evolving. As levothyroxine is a life-long medication it is important to avoid risks from periods of overtreatment or undertreatment. For the subset of patients not restored to baseline health with levothyroxine, causes arising from all aspects of the patient's life (co-existent medical conditions, stressors, lifestyle, psychosocial factors) should be broadly considered. If such factors do not appear to be contributing, and biochemical euthyroidism has been successfully maintained, there may be benefit to a trial of combination therapy with levothyroxine and liothyronine. This is not supported by the majority of randomized clinical trials, but may be supported by other studies providing lower quality evidence and by animal studies. Given this discrepancy, it is important that any trial of combination therapy only be continued as long as a patient benefit is being enjoyed. Monitoring for adverse effects, particularly in older or frail individuals, is necessary and combination therapy should not be utilized during pregnancy. A sustained release liothyronine preparation has completed phase 1 testing and may soon be available for better designed and powered studies assessing whether combination therapy provides superior therapy for hypothyroidism.

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Topics: Levothyroxine (61%), Liothyronine (57%), Thyroid function (55%)

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Journal ArticleDOI: 10.7326/0003-4819-117-12-1010
Abstract: ▪Objective:To determine whether simultaneous ingestion of ferrous sulfate and thyroxine reduces the efficacy of thyroid hormone in patients with primary hypothyroidism. ▪Design:Uncontrolle...

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Topics: Primary hypothyroidism (64%), Thyroid (51%)

195 Citations


Open accessJournal ArticleDOI: 10.1111/J.1365-2125.2010.03722.X
David G. Bailey1, David G. Bailey2Institutions (2)
Abstract: A new type of interaction in which fruit juices diminish oral drug bioavailability through inhibition of uptake transport is the focus of this review. The discovery was based on an opposite to anticipated finding when assessing the possibility of grapefruit juice increasing oral fexofenadine bioavailability in humans through inhibition of intestinal MDR1-mediated efflux transport. In follow-up investigations, grapefruit or orange juice at low concentrations potentially and selectively inhibited in vitro OATP1A2-mediated uptake compared with MDR1-caused efflux substrate transport. These juices at high volume dramatically depressed oral fexofenadine bioavailability. Grapefruit was the representative juice to characterize the interaction subsequently. A volume–effect relationship study using a normal juice amount halved average fexofenadine absorption. Individual variability and reproducibility data indicated the clinical interaction involved direct inhibition of intestinal OATP1A2. Naringin was a major causal component suggesting that other flavonoids in fruits and vegetables might also produce the effect. Duration of juice clinical inhibition of fexofenadine absorption lasted more than 2 h but less than 4 h indicating the interaction was avoidable with appropriate interval of time between juice and drug consumption. Grapefruit juice lowered the oral bioavailability of several medications transported by OATP1A2 (acebutolol, celiprolol, fexofenadine, talinolol, L-thyroxine) while orange juice did the same for others (atenolol, celiprolol, ciprofloxacin, fexofenadine). Juice clinical inhibition of OATP2B1 was unresolved while that of OATP1B1 seemed unlikely. The interaction between grapefruit juice and etoposide also seemed relevant. Knowledge of both affected uptake transporter and drug hydrophilicity assisted prediction of the clinical interaction with grapefruit or orange juice.

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Topics: Grapefruit juice (76%), Orange juice (73%), Naringin (56%) ... read more

189 Citations


Open accessJournal ArticleDOI: 10.1001/JAMA.283.21.2822
07 Jun 2000-JAMA
Abstract: ContextThe effect of calcium carbonate on the absorption of levothyroxine has not been studied systematically. Such a potential drug interaction merits investigation because concurrent treatment with both drugs is common, particularly in postmenopausal women.ObjectiveTo investigate the potential interference of calcium carbonate in the absorption of levothyroxine.DesignProspective cohort study conducted from November 1998 to June 1999, supplemented with an in vitro study of thyroxine (T4) binding to calcium carbonate.SettingVeterans Affairs Medical Center in West Los Angeles, Calif.PatientsTwenty patients (age range, 27-78 years; n=11 men) with hypothyroidism who were taking a stable long-term regimen of levothyroxine were included in the study. All patients had serum free T4 and thyrotropin values in the normal range before beginning the study.InterventionSubjects were instructed to take 1200 mg/d of elemental calcium as calcium carbonate, ingested with their levothyroxine, for 3 months.Main Outcome MeasuresLevels of free T4, total T4, total triiodothyronine (T3), and thyrotropin, measured in all subjects at baseline (while taking levothyroxine alone), at 2 and 3 months (while taking calcium carbonate and levothyroxine), and 2 months after calcium carbonate discontinuation (while continuing to take levothyroxine).ResultsMean free T4 and total T4 levels were significantly reduced during the calcium period and increased after calcium discontinuation. Mean free T4 levels were 17 pmol/L (1.3 ng/dL) at baseline, 15 pmol/L (1.2 ng/dL) during the calcium period, and 18 pmol/L (1.4 ng/dL) after calcium discontinuation (overall P<.001); mean total T4 levels were 118 nmol/L (9.2 µg/dL) at baseline, 111 nmol/L (8.6 µg/dL) during the calcium period, and 120 nmol/L (9.3 µg/dL) after calcium discontinuation (overall P=.03). Mean thyrotropin levels increased significantly, from 1.6 mIU/L at baseline to 2.7 mIU/L during the calcium period, and decreased to 1.4 mIU/L after calcium discontinuation (P=.008). Twenty percent of patients had serum thyrotropin levels higher than the normal range during the calcium period; the highest observed level was 7.8 mIU/L. Mean T3 levels did not change during the calcium period. The in vitro study of T4 binding to calcium showed that adsorption of T4 to calcium carbonate occurs at acidic pH levels.ConclusionsThis study of 20 patients receiving long-term levothyroxine replacement therapy indicates that calcium carbonate reduces T4 absorption and increases serum thyrotropin levels. Levothyroxine adsorbs to calcium carbonate in an acidic environment, which may reduce its bioavailability.

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Topics: Elemental calcium (64%), Calcium (61%), Levothyroxine (52%)

186 Citations


Journal ArticleDOI: 10.1016/J.BEEM.2009.06.006
Abstract: Food, dietary fibre and espresso coffee interfere with the absorption of levothyroxine. Malabsorptive disorders reported to affect the absorption of levothyroxine include coeliac disease, inflammatory bowel disease, lactose intolerance as well as Helicobacter pylori (H. pylori) infection and atrophic gastritis. Many commonly used drugs, such as bile acid sequestrants, ferrous sulphate, sucralfate, calcium carbonate, aluminium-containing antacids, phosphate binders, raloxifene and proton-pump inhibitors, have also been shown to interfere with the absorption of levothyroxine.

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Topics: Levothyroxine (55%)

181 Citations


Open accessJournal ArticleDOI: 10.1210/JC.2009-0860
Abstract: Context: Patients treated with levothyroxine typically ingest it in a fasting state to prevent food impairing its absorption. The serum thyrotropin concentration is the therapeutic index of levothyroxine action. Objective: The study objective was to determine the effect of the timing of levothyroxine administration in relationship to food on serum thyrotropin levels. Design: Participants were randomized to one of six sequences, each consisting of three 8-wk regimens in a three-period crossover design. These regimens were in a fasting state, at bedtime, and with breakfast. The concentrations of TSH, free T4, and total T3 during each of the three timing regimens were documented. The primary outcome was the difference between serum TSH concentrations under fasting conditions compared with concentrations during the other 8-wk regimens. Setting: The study was conducted in an academic medical center. Participants: Study participants were receiving levothyroxine for treatment of hypothyroidism or thyroid cancer. Results: Sixty-five patients completed the study. The mean thyrotropin concentration was 1.06 ± 1.23 mIU/liter when levothyroxine was administered in the fasting state. When levothyroxine was taken with breakfast, the serum thyrotropin concentration was significantly higher (2.93 ± 3.29 mIU/liter). When levothyroxine was taken at bedtime, the serum TSH concentration was also significantly higher (2.19 ± 2.66 mIU/liter). Conclusion: Nonfasting regimens of levothyroxine administration are associated with higher and more variable serum TSH concentrations. If a specific serum TSH goal is desired, thereby avoiding iatrogenic subclinical thyroid disease, then fasting ingestion of levothyroxine ensures that TSH concentrations remain within the narrowest target range.

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Topics: Levothyroxine (61%)

158 Citations


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