Effects of grapefruit juice on the absorption of levothyroxine

Lilja, Jari J.; Laitinen, Kalevi; Neuvonen, Pertti J.

doi:10.1111/j.1365-2125.2005.02433.x

Cited by 59 publications

(42 citation statements)

References 19 publications

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“…Unfortunately, it was not possible to confirm this hypothesis as these patients declined further repeat testing using crushed L-T 4 tablets. We did not specifically ask about grapefruit juice (18) or ingestion of soy protein supplements (19), both of which have been shown to affect absorption. It is, however, unlikely that this could have explained the lack of TSH suppression observed as massive quantities would have been needed to produce the elevation in TSH levels in those patients who did not respond.…”

Section: Discussionmentioning

confidence: 99%

A thyroxine absorption test followed by weekly thyroxine administration: a method to assess non-adherence to treatment

Walker

Shillo

Ibbotson

et al. 2013

European Journal of Endocrinology

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Objective: For patients who remain hypothyroid despite the administration of what would seem adequate doses of levothyroxine (L-T 4 ), the underlying cause can be difficult to determine. The possibility of a biological cause should first be explored; however, in the majority of cases, poor adherence to medication is likely to be the main cause of treatment failure. When non-adherence is suspected but not volunteered, options to confirm the suspicion are limited. In this study, we identified patients for whom known drugs and pathological causes of L-T 4 malabsorption were excluded, and despite often high doses of L-T 4 , the patients remained hypothyroid. Design: Using a weight-determined oral L-T 4 bolus administration, absorption was initially assessed in 23 patients. In nearly all patients, this was shown to be maximal at 120 min post-ingestion. This was then followed by the continued administration of a weekly T 4 bolus for a 4-week period after which TSH and free T 4 (fT 4 ) levels were recorded. Results: All patients showed a rise in fT 4 at 120 min following the administration of the L-T 4 bolus, with a mean increase of 54G3% from baseline. Following the treatment period, using an equivalent weekly L-T 4 dose, which was significantly less than that of the daily dose taken by the patients before the test, TSH reduced from baseline in w75% of cases. Conclusion: Using this combination of tests allows significant malabsorptive problems to be identified first and then potential non-adherence to be demonstrated. A management plan can then be implemented to increase adherence, aiming to improve treatment outcomes.European Journal of Endocrinology 168 913-917

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Section: Discussionmentioning

confidence: 99%

A thyroxine absorption test followed by weekly thyroxine administration: a method to assess non-adherence to treatment

Walker

Shillo

Ibbotson

et al. 2013

European Journal of Endocrinology

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“…etoposide, L-thyroxine). [19][20][21][22] This seeming dichotomy is explained by differential effects on metabolizing enzymes (i.e. CYP3A) and transporters (i.e.…”

Section: Types Of Drug and Nutrition Interactionsmentioning

confidence: 99%

Drug and nutrition interactions: not just food for thought

Boullata

2013

J Clin Pharm Ther

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Summary What is known and objective The management of drug‐drug interactions – from recognition of the interaction potential, to addressing the negative consequences – are well‐recognized and avoided, or rapidly addressed when identified clinically. Drug‐nutrition interactions are no less important than drug‐drug interactions in patient care. Unfortunately, beyond those caused by food, these interactions are less commonly recognized or identified and managed. This article will re‐introduce the topic of drug‐nutrition interactions to clinicians. Comment Although many clinicians are acutely aware of and vigilant for potential drug‐drug interactions, most are less aware of the possibility of drug‐nutrition interactions beyond classic food‐drug interactions. Interaction can occur between a drug and a nutrient, multiple nutrients, food in general, specific foods or components, or nutrition status. An interaction is considered clinically significant if it alters therapeutic drug response and/or compromises nutrition status. Mechanistically the interactions may be physicochemical reactions, actions at membrane transporters or metabolizing enzymes, or an influence on physiologic function. Appreciating the many types of drug‐nutrition interactions will aid the clinician and have the potential to influence patient outcome. What is new and conclusion Ongoing advances in knowledge about drug and nutrition interactions have potential to improve patient care. Drug‐nutrition interactions need to be better recognized, understood on a mechanistic basis, predicted, and managed as necessary.

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“…12,13 Coffee has been specially described to diminish T 4 absorption, 16 as have grapefruit juice (but not orange juice), 17,18 papaya fruit, 19 and dietary fiber, including bran. 16 Milk and other dairy products, and perhaps other foods that are rich in calcium, may impair the bioavailability of T 4 (see the next section), although there is no formal study of the interaction.…”

Section: Food and Absorption Of Tmentioning

confidence: 99%