Delayed Intestinal Absorption of Levothyroxine

Benvenga, Salvatore; Bartolone, L.; Squadrito, S.; Giudice, Francesco Lo; Trimarchi, Francesco

doi:10.1089/thy.1995.5.249

Cited by 129 publications

(110 citation statements)

References 8 publications

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“…The absorption of levothyroxine occurs within an interval of 3 hrs of ingestion, mainly in the jejunum and ileum (18)(19)(20). On average, approximately 70%-80% of the available tablet dose is absorbed by the euthyroid individual, and this absorption rate may diminish in the hypothyroid patient (18).…”

Section: Drug Interaction and Concomitant Diseasesmentioning

confidence: 99%

The difficult patient: drug interaction and the influence of concomitant diseases on the treatment of hypothyroidism

Ward

2010

Arq Bras Endocrinol Metab

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summaRyAlthough most hypothyroid patients do well with one single tablet of thyroxine daily, approximately 10% are dissatisfied and another important group of patients is difficult to control. We reviewed the most common causes for frequent-dose adjustment or high-dose requirement, including poor compliance with therapy and inadequate medication. Since these two causes have been ruled out, drug interaction and other concomitant diseases need to be investigated. Requirements of thyroxine increase in all conditions characterized by impaired gastric acid secretion. Proton-pump inhibitors, antacids and a long list of drugs may decrease thyroxine absorption. In addition, a series of diseases including celiac disease and chronic inflammatory intestinal diseases, as well as nutritional habits may be important in patient control. Finally, we mention the effects of a growing list of drugs and thyroid disruptors that may also affect thyroid hormone metabolism at many levels. Arq Bras Endocrinol Metab. 2010;54(5):435-42 Keywords Medication-taking behavior; compliance; bioequivalence; absorption; nutritional habits sumáRio Embora a maior parte dos pacientes com hipotiroidismo fique bem com um único comprimido diário de tiroxina, aproximadamente 10% não ficam satisfeitos e outro importante grupo de pacientes apresenta controle difícil. Foram revistas as causas mais comuns para necessidades frequentes de ajuste de dose ou uso de dose elevadas, incluindo falta de adesão à terapia e medicação inadequada. Descartando-se essas duas causas, é necessário investigar o uso de drogas e a presença de doenças concomitantes. Existe necessidade maior de tiroxina quando diminui a secreção ácida do estômago. Inibidores de bomba de prótons, antiácidos e uma longa lista de drogas podem dificultar a absorção da tiroxina. Várias doenças, incluindo a doença celíaca e as doenças intestinais inflamatórias crônicas, além dos hábitos alimentares, são importantes no controle do paciente hipotiroideo. Finalmente, foram mencionados os efeitos de uma lista crescente de drogas e disruptores que podem afetar o metabolismo tiroidiano em diferentes níveis. Arq Bras Endocrinol Metab. 2010;54(5):435-42 Descritores

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Section: Drug Interaction and Concomitant Diseasesmentioning

confidence: 99%

The difficult patient: drug interaction and the influence of concomitant diseases on the treatment of hypothyroidism

Ward

2010

Arq Bras Endocrinol Metab

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“…One such factor is the amount of LT 4 absorbed in the gastrointestinal tract, which is altered by various medical disorders (10)(11)(12), several medications (13)(14)(15)(16), and food and drink (17)(18)(19). The timing of LT 4 administration also has an impact on its absorption (18,(20)(21)(22).…”

Section: Introductionmentioning

confidence: 99%

Levothyroxine Replacement Doses Are Affected by Gender and Weight, But Not Age

Devdhar

Drooger

Pehlivanova

et al. 2011

Thyroid

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Background: Body weight (BW) and age have been shown to affect the dose of levothyroxine (LT 4 ) that results in normalization of serum thyroid-stimulating hormone (TSH) in hypothyroid patients. Our objective was to determine whether gender, menstrual status, and ideal BW (IBW) also affect the LT 4 dose required to achieve a serum TSH within the normal range. Methods: We retrospectively reviewed the charts of patients being treated for primary hypothyroidism who had TSH values within a normal range. We selected patients aged 18-85 years who were taking LT 4 without any confounding medications, and who had no serious chronic conditions. Their LT 4 doses, referred to here as LT 4 dose requirements, based on both BW and IBW were documented. The relationship between gender, menstrual status, age, serum TSH concentrations, and the degree of overweight on LT 4 dose requirements were determined using multivariate analyses. Results: Women were significantly more overweight than men (ratio of BW/IBW was 1.35 for women vs. 1.17 for men, p < 0.0001). LT 4 requirements based on BW did not differ by gender when age was included in the model. However, when degree of overweight was also included, men required lower LT 4 doses than both premenopausal women (1.34 mg/kg vs. 1.51 mg/kg, p ¼ 0.038) and menopausal women (1.34 mg/kg vs. 1.49 mg/ kg, p ¼ 0.023). When examining IBW using a model incorporating age, men also required lower LT 4 doses than both premenopausal women (1.64 mg/kg vs. 1.92 mg/kg, p ¼ 0.0033) and menopausal women (1.64 mg/kg vs. 1.90 mg/kg, p ¼ 0.0024). Serum TSH concentrations were not significantly different in any of the gender groups. There was no relationship between serum TSH and either age or BW. The initial serum TSH concentration was by design with the normal range, but the concentration within that range was not a significant predictor of the LT 4 replacement dose in any of the models. Conclusion: In contrast to previous studies suggesting that age affects LT 4 replacement requirements, we found that age-based differences in doses are secondary to differences in BW and gender. In addition, in contrast to prior studies showing that lean body mass, but not gender, affected LT 4 dose, we instead found a significant impact of gender. Gender-based differences in dose requirement only became apparent either when IBW was used to correct for the dose or when degree of overweight was included in the model. Gender differences in LT 4 dose requirement exist, but are masked unless gender-based differences in degree of overweight are also considered.

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“…In such a situation, physicians need to search for causes of decreased absorption of thyroxine or increased demand for thyroxine (Table 1). [4][5][6][7] Levothyroxine sodium is the most commonly…”

Section: Discussionmentioning

confidence: 99%

“…3,8 Adequate gastric acidity is required to dissolve the salt-based tablet, allowing for intestinal absorption. 4 Approach to treatment-refractory hypothyroidism An approach to treating hypothyroidism refractory to supernormal doses of thyroxine is summarized in Figure 1. Common causes for treatment -refractory hypothyroidism include poor adherence to therapy and interactions between thyroxine and medication or food.…”

Section: Treatment-refractory Hypothyroidismmentioning

confidence: 99%