Tablet formulation of levothyroxine is absorbed less well than powdered levothyroxine

Parameters to Consider for Successful Medication Use in Older Adults - an AGePOP Review

Older adults are the main users of medicine and due to their multimorbidity are often faced/confronted with a complex medication management. This review article provides a brief overview on aspects of medication management such as maintaining a stock of the required medicine, understanding and following the instructions for use, coping with the primary and secondary packaging as well as preparation prior to use. The main focus however is on the drug intake itself and provides an overview about the current understanding of real life dosing conditions of older adults and geriatric patients. Furthermore, it elaborates the acceptability of dosage forms, in particular solid oral dosage forms as they represent the majority of dosage forms taken by these patient populations. An improved understanding of the needs of older adults and geriatric patients, their acceptability of various dosage forms and the circumstances under which they manage their medications, will make the design of more patient-centric drug products possible.

Levothyroxine: Conventional and novel drug delivery formulations

Despite the fact that levothyroxine is one of the most prescribed medications in the world, its bioavailability has been reported to be impaired by many factors, including interfering drugs or foods and concomitant diseases, and persistent hypothyroidism with a high dose of levothyroxine is thus elicited. Persistent hypothyroidism can also be induced by noninterchangeability between formulations and poor compliance. To address these issues, some strategies have been developed. Novel formulations (liquid solutions and soft-gel capsules) have been designed to eliminate malabsorption. Some other delivery routes (injections, suppositories, sprays, and sublingual and transdermal administrations) are aimed at circumventing different difficulties in dosing, such as thyroid emergencies and dysphagia. Moreover, nanomaterials have been used to develop delivery systems for the sustained release of levothyroxine to improve patient compliance and reduce costs. Some delivery systems encapsulating nanoparticles show promising release profiles. In this review, we first summarize the medical conditions that interfere with the bioavailability of oral levothyroxine and discuss the underlying mechanisms and treatments. The efficacy of liquid solutions and soft-gel capsules are systematically evaluated. We further summarize the novel delivery routes for levothyroxine and their possible applications. Nanomaterials in the levothyroxine field are then discussed and compared based on their load and release profile. We hope the article provides novel insights into the drug delivery of levothyroxine.

Switching from the tablet to the powder formulation of levothyroxine corrects severe hypothyroidism in a patient with lactose intolerance

We describe a case of a 38-year-old woman who, after radioactive iodine therapy for Graves' disease, developed severe hypothyroidism despite receiving a high dose of levothyroxine (L-T4) tablet as replacement therapy. Her thyroid stimulating hormone (TSH) remained to be high despite the dose of L-T4 tablets to 400 μg/day after treatment for hypothyroidism, and the patient complained of general malaise and edema of the legs. Reduced intestinal absorption of L-T4 is the most common cause of failure to achieve the therapeutic target in hypothyroid patients receiving replacement therapy. She was admitted to our hospital for severe hypothyroidism due to resistance to treatment with L-T4 tablet. Our patient was found to have lactose intolerance (LI) by a detailed examination during hospitalization. Therefore, we assumed that LI was impairing intestinal absorption of L-T4 tablet in our patient, leading to severe hypothyroidism. The patient was switched to the powder formulation of L-T4 at the same daily dose, and serum levels of thyroid-stimulating hormone and thyroid hormones normalized. This is the case in which hypothyroidism due to reduced absorption of L-T4 tablet in a patient with LI was resolved by switching to L-T4 powder formulation.

Treatment of hypothyroidism in infants, children and adolescents

In 2014, treatment guidelines from the American Thyroid Association reflected the general consensus that levothyroxine (LT4), adjusted to maintain a normal thyrotropin (TSH) level, is the preferred method for treatment of hypothyroidism. Although this is generally applicable to children, there are subsets of children for whom the diagnosis and treatment of hypothyroidism are problematic. These include children with congenital hypothyroidism (CH), low birth weight (LBW) and very low birth weight (VLBW), Down syndrome (DS), subclinical hypothyroidism, and obesity. In this Review, we focus on the progress and remaining pitfalls in diagnosis and treatment of hypothyroidism in these and other groups.

New Formulations of Levothyroxine in the Treatment of Hypothyroidism: Trick or Treat?

Background: Levothyroxine (LT4) as a medication is used by up to 5.3% of the adult population. For optimal efficacy, the traditional tablet formulation (LT4tab) requires that patients avoid concomitant ingestion with food, drinks, and certain medications, as well as excellent patient compliance. Some comorbidities influence bioavailability of LT4 and may mandate repeated dose adjustments. Summary: New LT4 formulations (soft gel [LT4soft] and liquid [LT4liq]) containing predissolved LT4 are claimed to improve bioavailability, presumably by facilitating absorption. Thus, these formulations may well be more suitable than LT4tab for patients whose daily requirements are subjected to variations in bioavailability. Here, we review the evidence and indications for use of new LT4 formulations and highlight areas of uncertainty that are worthy of further investigation. While bioequivalence is established for LT4soft and LT4liq administered to healthy volunteers compared with LT4tab in pharmacokinetic (PK) studies, therapeutic equivalence of the new formulations seems to be different in several clinical settings. Some evidence suggests that new formulations of LT4 may mitigate against the strict requirements relating to concomitant ingestion with food, drinks, and certain medications, which apply to traditional LT4 tablets. The principal indication is in selected patients with disease fluctuations and intermittent therapies with interfering medications, where the need for frequent dose adjustments and office visits may be diminished. Whether the use of LT4soft or LT4liq in patients with impaired gastric acid secretion results in better control of hypothyroidism than LT4tab remains unclear. Conclusions: The evidence in favor of using LT4soft and LT4liq in clinical practice over LT4tab is weak, and the underlying putative PK mechanisms unclear. Additional studies to investigate these potential benefits, define the cost-effectiveness, and understand the PK mechanisms involved with new LT4 formulations are needed.

A Case of Hashimoto's Thyroiditis with Multiple Drug Resistance and High Expression of Efflux Transporters

CONTEXT

Hashimoto's thyroiditis is the most common cause of hypothyroidism. Patients usually respond well to oral synthetic thyroxine (levothyroxine); however, for unknown reasons some individuals present with treatment-resistant Hashimoto thyroiditis. In cases of cancer and certain infectious diseases, the ATP binding cassette (ABC) transporters have been implicated in multidrug resistance, and we hypothesized and investigated a role of ABC transporters in drug-resistant Hashimoto's thyroiditis.

CASE DESCRIPTION

The patient whose case we report had a history of Hashimoto's thyroiditis, immune thrombocytopenia, and refractory hypertension, with varying treatment resistance to the oral medications prescribed for each condition. In order to establish or exclude a genetic basis for her illness, we examined the patient's gene expression profiles using peripheral blood leukocytes, and found that ABCG2/BCRPexpression was significantly high compared with healthy volunteers. Also, the increased daunomycin efflux capacity of our patient's lymphocytes was successfully inhibited by fumitremorgin C, a specific ABCG2/BCRP inhibitor, and the patient's level of thyroid-stimulating hormone increased by 248.6% after administration of intact levothyroxine tablets but decreased by 45.1% when tablets were crushed. Her average blood pressure decreased from 166.3/108.5 mmHg to 125.9/78.8 mmHg when switching from intact to crushed losartan tablets.

CONCLUSIONS

High expression and accelerated efflux transporter activity of ABCG2/BCRP in the small intestine are expected to contribute to the ineffectiveness of orally administered intact tablets in cases with treatment-resistant Hashimoto's thyroiditis, and crushed tablets can be more effective for some of these patients.

Hypothyroidism following gastric sleeve surgery resolved by ingesting crushed thyroxine tablets

Bariatric procedures for weight loss have increased in the past few decades. Levothyroxine malabsorption has been reported following gastric bypass; however, few studies have addressed this issue after gastric sleeve procedures. Levothyroxine dosing is usually weight based and administered at approximately 1.6 μg/kg body weight. Absorption occurs mainly in the jejunum and upper ileum, which can be altered by gastric pH, other drugs, food, and other factors. We present a 35-year-old woman with longstanding iatrogenic hypothyroidism treated with thyroxine, whose thyroid-stimulating hormone level rose following a gastric sleeve procedure despite taking levothyroxine daily.

Efficacy and Safety of Once-Weekly Thyroxine for Thyroxine-Resistant Hypothyroidism

Context

Noncompliance with thyroxine therapy is the most common cause of poor control of hypothyroidism. An open-label prospective study to compare once-weekly thyroxine (OWT) with standard daily thyroxine (SDT) was undertaken.

Design

Patients taking thyroxine doses of >3 μg/kg/d, with or without normalization of TSH, were included and administered directly observed OWT or nonobserved SDT according to patient preference based on their weight for 6 weeks. Furthermore, patients on OWT were advised to continue the same at home without supervision.

Results

Twenty six of 34 patients on OWT and 7 of 18 patients on SDT achieved a TSH <10 μIU/mL (P < 0.05), and 2 patients from the SDT arm were lost to follow-up. During home treatment, 15 of 25 at 12 weeks and 19 of 23 contactable patients at a median follow-up of 25 months maintained TSH below target. Thyroxine absorption test was unable to predict normalization of TSH at 6 weeks of OWT therapy. No adverse events were seen with OWT-treated patients over the 12-week follow-up period. OWT has significantly higher efficacy (OR = 5.1) than SDT for patients with thyroxine-resistant hypothyroidism and is not associated with side effects.

Conclusion

OWT benefits a majority of patients in the long-term treatment of thyroxine-resistant hypothyroidism, in the real-world setting.

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

OBJECTIVE

For patients who remain hypothyroid despite the administration of what would seem adequate doses of levothyroxine (L-T4), 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-T4 malabsorption were excluded, and despite often high doses of L-T4, the patients remained hypothyroid.

DESIGN

Using a weight-determined oral L-T4 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 T4 bolus for a 4-week period after which TSH and free T4 (fT4) levels were recorded.

RESULTS

All patients showed a rise in fT4 at 120 min following the administration of the L-T4 bolus, with a mean increase of 54±3% from baseline. Following the treatment period, using an equivalent weekly L-T4 dose, which was significantly less than that of the daily dose taken by the patients before the test, TSH reduced from baseline in ~75% 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.

A Review of the Pharmacokinetics of Levothyroxine for the Treatment of Hypothyroidism

Thyroxine hormone has been recognised since the early part of the nineteenth century and levothyroxine has been available since the mid-nineteenth century as a replacement for deficient thyroid hormones. While levothyroxine remains the staple treatment for hypothyroidism even to this day, its optimal use can be challenging. As is often the case with older drugs, the pharmacokinetics of levothyroxine is often under-appreciated or misunderstood and many factors influence the optimal dosing of levothyroxine. This article will review the pharmacokinetics of levothyroxine in the treatment of hypothyroidism and highlight major concepts that should aid both clinicians and researchers.

Pseudomalabsorption de L-thyroxine: une forme de pathomimie

INTRODUCTION

Thyroxine supplementation of patients with hypothyroidism is usually simple. A few patients, however, continue to present elevated TSH levels despite large doses of L-thyroxine.

CASE

We report the case of a 71-year-old women who had had a thyroidectomy 10 years earlier and had since been hospitalized repeatedly for profound hypothyroidism. Despite her consistent claims of good adherence to her treatment regimen, we considered the diagnosis of L-thyroxine pseudomalabsorption and confirmed it by thyroid hormone absorption tests.

DISCUSSION

L-thyroxine pseudomalabsorption due to concealed poor treatment adherence should be considered after ruling out drug or dietary interference and true organic malabsorption. Diagnosis of this factitious disease can be confirmed by L-thyroxine absorption tests.