New levothyroxine formulation meeting 95-105% specification over the whole shelf-life: results from two pharmacokinetic trials

Exploring Microemulsion Systems for the Incorporation of Glucocorticoids into Bacterial Cellulose: A Novel Approach for Anti-Inflammatory Wound Dressings

The effective pharmacological treatment of inflamed wounds such as pyoderma gangraenosum remains challenging, as the systemic application of suitable drugs such as glucocorticoids is compromised by severe side effects and the inherent difficulties of wounds as drug targets. Furthermore, conventional semi-solid formulations are not suitable for direct application to open wounds. Thus, the treatment of inflamed wounds could considerably benefit from the development of active wound dressings for the topical administration of anti-inflammatory drugs. Although bacterial cellulose appears to be an ideal candidate for this purpose due to its known suitability for advanced wound care and as a drug delivery system, the incorporation of poorly water-soluble compounds into the hydrophilic material still poses a problem. The use of microemulsions could solve that open issue. The present study therefore explores their use as a novel approach to incorporate poorly water-soluble glucocorticoids into bacterial cellulose. Five microemulsion formulations were loaded with hydrocortisone or dexamethasone and characterized in detail, demonstrating their regular microstructure, biocompatibility and shelf-life stability. Bacterial cellulose was successfully loaded with the formulations as confirmed by transmission electron microscopy and surprisingly showed homogenous incorporation, even of w/o type microemulsions. High and controllable drug permeation through Strat-M® membranes was observed, and the anti-inflammatory activity for permeated glucocorticoids was confirmed in vitro. This study presents a novel approach for the development of anti-inflammatory wound dressings using bacterial cellulose in combination with microemulsions.

Within-subject pharmacokinetic variability has a strong influence on individual exposure ratios in bioequivalence studies, hence on drug formulation interchangeability

INTRODUCTION

Bioequivalence between a reference and a generic drug is based on the hypothesis that a ± 20% change in blood exposure (or ± 10% for drugs with narrow therapeutic index, NTI) following the generic/reference switch will not have any therapeutic consequences. However, the individual exposure ratio between generic and reference can be higher than 1.20 (or 1.10). This study aims to analyse the different parameters influencing the individual exposure ratio, hence the conditions for reference/generic interchangeability.

METHODS

Bioequivalence studies with a double cross-over design for a virtual drug were simulated using 100 random sets of 12, 24, 48 or 100 pairs of areas under the curve (AUC), varying the generic/reference AUC geometric mean ratios between 0.80 and 1.25 and the within-subject exposure variance of the reference and the generic formulations.

RESULTS

The proportion of subjects with an exposure generic/reference ratio outside the ± 10% or ± 20% acceptance intervals increases when (1) the reference within-subject variance increases; (2) the ratio of the generic within-subject variance on the reference within-subject variance increases; and (3) the generic/reference mean AUC ratio diverges from 1.0. When only considering replicated administrations of the reference, the individual exposure ratio increases with the within-subject variance, yielding values outside the usually accepted individual exposure ratio range of 0.5 to 2 for drugs with narrow therapeutic index as soon as the within-subject variance standard deviation is ≥ 0.25 (equivalent to within-patient CV% > 25%).

CONCLUSIONS

Interchangeability between reference and generic formulations, especially for drugs with narrow therapeutic index can only be assumed if, the within-subject variance of generic is less or equal to the within-subject variance of reference or, if this is not the case, if the distribution of the generic/generic individual exposure ratios is included within the therapeutic margins of the reference drug.

Levothyroxine Bioequivalence Study and Its Narrow Therapeutic Index: Comparative Bioavailability Results Between Two Formulations Available in Latin America

INTRODUCTION

The history of levothyroxine has been linked to advances in the treatment of thyroid disease and to date it is the standard therapy for the treatment of hypothyroidism. Bioequivalence studies are the most widely used method to demonstrate interchangeability, although controversy persists regarding the best design for this molecule declared as a narrow therapeutic index product in many countries. This study aimed to evaluate the pharmacokinetic profile of two formulations of levothyroxine to determine bioequivalence between them.

METHODS

This two-period, randomized, crossover, blind study was conducted in 80 healthy volunteers, of both sexes, using a single levothyroxine dose of 600 μg with a washout period of 42 days. Blood sampling was performed at - 30 min, - 15 min, and 0 h pre-dose and 30 min, 1, 1.5, 2, 2.5, 3, 4, 6, 8, 10, 12, 16, 24, and 48 h post-dose.

RESULTS

A total of 78 subjects successfully completed both periods. There were no serious adverse events during the study and both formulations were well tolerated. Baseline correction of serum levothyroxine concentrations was performed before statistical analysis. The mean maximum plasma concentration of the test product (Levotiroxina MK®) was 57.49 ng/mL while for the reference product it reached 59.32 ng/mL. Importantly, both test and reference formulations reached maximum concentrations in plasma at about the same time. The areas under the pharmacokinetic curves with the test product showed AUC0-t of 1407.1 ng h/mL and the reference product 1394.3 ng h/mL. The bioequivalence statistical analysis showed that the 90% confidence interval (CI90%) of the ratio of test over reference formulation was within the bioequivalence margins of 90-111%. For Cmax, the test/reference ratio was 96.2% with CI90% of 91.6-100.9%, and for AUC0-t the test/reference ratio was 99.9 with CI90% of 93.3-107.0%.

CONCLUSIONS

Both formulations have the same pharmacokinetic profile and are bioequivalent in the narrow therapeutic index required by some health authorities.

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.

Interchangeability between Generic and Reference Products: Limits of Average Bioequivalence Methodology

Marketing authorisation of generic drugs is based on a demonstration of the "average" bioequivalence (ABE), with acceptance limits of 0.8-1.25 for the 90% confidence interval (CI) of the ratio (generic versus reference) of geometric means of exposure (whole blood, serum or plasma drug concentration). However, when interchangeability of reference by one generic is considered during treatment of a given patient, such methodology cannot guarantee the lack of therapeutic impact especially for drugs with narrow therapeutic index. This review article describes the basis and limits of ABE methodology, and the adaptations that have been proposed by regulatory agencies. For highly variable drugs, given their large therapeutic margin, regulatory agencies even allow widening of the bioequivalence acceptance limits. For drugs with a narrow therapeutic index, the average bioequivalence methodology has been amended differently by regulatory agencies. The European Medicine Agency only requires the narrowing of the ABE acceptance limits to the 0.9-1.10 range. The US Food and Drug Administration (FDA) has proposed to narrow the ABE acceptance limits according to the reference within-subject variance. The FDA requires a fully replicate cross-over study (with four periods) which allows one to compare the within-subject variance between generic and reference drug, and to detect any subject-by-formulation interaction. Indeed, any within-subject variance difference or subject by formulation interaction is an obstacle to interchangeability at the individual level. These amendments for the ABE do not fundamentally change the fact that individual ratios of exposure (generic/reference) will vary to a larger extent than the ratio of their means. For these reasons, since true individual bioequivalence studies cannot be performed for practical reasons and statistical issues, one can suggest that, in addition to the usual average bioequivalence criteria, the limits of the 95% confidence interval of the individual generic/reference exposure ratios could be used to allow interchangeability during treatment (at least for narrow therapeutic index drugs). Limit values of such CI for interchangeability acceptance should be scaled to the therapeutic margin of the reference drug. Regulatory agencies could conduct calculations based on real datasets of bioequivalence studies to determine if such criteria could be acceptable to allow interchangeability.

Getting the levothyroxine (LT4) dose right for adults with hypothyroidism: opportunities and challenges in the use of modern LT4 preparations

Lifelong treatment with levothyroxine (LT4) is the mainstay of management for individuals with hypothyroidism. Many hypothyroid patients start LT4 treatment at a low dose (e.g. 25-50 µg), especially the elderly, those with residual thyroid function, those with low body weight, and those with significant (especially cardiac) comorbidities. Almost half of patients on LT4 replacement therapy demonstrate either under- or over-treatment. Many LT4 preparations have relatively large intervals between tablet strengths at the lower end of their dose ranges (providing 25 µg, 50 µg, and 75 µg tablets), which may represent a barrier to achieving the optimum maintenance treatment for some patients. The availability of intermediate tablet strengths of LT4 in the 25-75 µg range may facilitate precise and effective dose titration of LT4 and may also enable convenient maintenance regimens based on a single LT4 tablet daily, to support adherence to therapy.

Stability of levothyroxine tablets in blister packaging versus bottles and vials under simulated in-use conditions

Introduction

Levothyroxine, the standard-of-care treatment for hypothyroidism, is susceptible to degradation when exposed to light and moisture and is an FDA-designated narrow therapeutic index drug. In this report, we examined how different packaging (e.g., cold form blister packs, manufacturer’s bottles, or pharmacy amber vials) affects the physicochemical integrity and potency of levothyroxine in conditions simulating real-world patient use.

Methods

In part 1 of this study, we evaluated changes in the physicochemical properties (e.g., moisture gain, hardness, and disintegration time) of levothyroxine tablets stored in high-density polyethylene (HDPE) bottles, amber vials, and blister packs when exposed intermittently to different relative humidities (RH), 25 °C/75% RH and 25 °C/90% RH for 90 days, or 54 °C/75% RH continuously for 2 days. In part 2 of the study, we compared the potency of levothyroxine tablets in bottles and aluminum/aluminum cold form blister packs exposed to 28 °C/65% RH intermittently over 105 days and continuously over 30 days.

Results

Moisture content, hardness, and disintegration time were relatively unchanged for blister-packaged levothyroxine tablets under all conditions studied. Conversely, the physicochemical properties of tablets stored in amber vials and bottles were altered over time. Levothyroxine potency remained relatively consistent for blister-packaged tablets (100.8% at baseline, 99.6% at day 105) and decreased for bottled levothyroxine (101.4% at baseline to 93.9% at day 105).

Conclusion

Levothyroxine packaging can influence tablet integrity. Blister packages preserved physicochemical properties and potency better than bulk bottles. Additional studies are needed to determine the impact of packaging and changes in tablet integrity on patient outcomes.

Pharmacokinetics and Generic Drug Switching: A Regulator's View

There appears to be a mismatch between the assumed therapeutic equivalence of generic drugs, their interchangeability, and reported clinical discomfort following generic drug use and drug switches. In this article, we describe why we are of the opinion that the current regulatory approach to the evaluation of generic drugs based on average bioequivalence is sufficient to expect therapeutic equivalence in the clinical setting. This has often been debated, specifically as adverse drug reactions related to generic drug switches are regularly reported. We agree that clinical discomfort during a bioequivalent drug switch may indeed be caused by different exposures to the active substance. However, this difference in exposure is not a result of the characteristics or quality of generic drugs; it is caused by the pharmacokinetic within-subject variability of the active substance, i.e., the variability on the bioavailability of the active substance, when comparing two occasions of administration of the same drug product, to the same patient. Therefore, reported clinical discomfort following generic drug use and drug switches does not warrant a change in the regulatory approach to the evaluation of the bioequivalence of generic drugs. Switching from a brand-name drug to currently approved generic drugs, or between different generic drugs, will in principle result in comparable exposure, within boundaries determined by the within-subject variability of the pharmacokinetics of the active substance involved.

Why Were More Than 200 Subjects Required to Demonstrate the Bioequivalence of a New Formulation of Levothyroxine with an Old One?

At the request of French Regulatory Authorities, a new formulation of Levothyrox^® was licensed in France in 2017, with the objective of avoiding the stability deficiencies of an existing licensed formulation. Before launching the new formulation, an average bioequivalence (ABE) trial was conducted, having enrolled 204 subjects and selected for interpretation a narrow a priori bioequivalence range of 0.90-1.11. Bioequivalence was concluded. In a previous publication, we questioned the ability of an ABE trial to guarantee the switchability within patients of the new and old levothyroxine formulations. It was suggested that the two formulations should be compared using the conceptual framework of individual bioequivalence. The present paper is a response to those claiming that, despite the fact that ABE analysis does not formally address the switchability of the two formulations, future patients will nevertheless be fully protected. The basis for this claim is that the ABE study was established in a large trial and analyzed using a stringent a priori acceptance interval of equivalence. These claims are questionable, because the use of a very large number of subjects nullifies the implicit precautionary intention of the European guideline when, for a Narrow Therapeutic Index drug, it recommends shortening the a priori acceptance interval from 0.80-1.25 to 0.90-1.11.

Comparison of Safety Profiles of the New and Old Formulations of Levothyroxine in a First Global Introduction in France

BACKGROUND

Levothyroxine sodium marketed in France was reformulated following a French National Agency for Medicines and Health Products Safety request for a more stringent potency specification. Despite previously established purity and bioequivalence of the new and old formulations, reports of adverse events substantially increased following reformulation. This analysis evaluated the nature and relevance of the medically confirmed safety reports.

METHODS

Spontaneous and solicited individual case safety reports in France were retrieved from 26 March 2015 to 30 June 2016 (old formulation) and 26 March 2017 to 30 June 2018 (new formulation). Rates of reports and adverse events were calculated for the overall patient population and for at-risk subgroups. Adverse events delineated by thyroid-stimulating hormone levels were evaluated.

RESULTS

A total of 295 and 42 775 reports for the old formulation and new formulation, respectively, were retrieved, with 149 and 5503 medically confirmed. The most common medically confirmed adverse events were consistent with the known safety profile of levothyroxine, with generally comparable rates between both formulations (range of differences, 1.8-4.1%). Most cases were not serious (old formulation, 65.8%; new formulation, 78.7%). Reporting rates were similar or higher for the old formulation within subgroups of at-risk patients. Nature/distributions of adverse events by thyroid-stimulating hormone levels as determined by both the marketing authorization holder of levothyroxine and the French National Agency for Medicines and Health Products Safety were similar.

CONCLUSIONS

The new formulation safety profile aligns with the established profile of the old formulation of levothyroxine. The benefit-risk profile is unchanged, such that the benefits of using the new formulation in the approved indications outweigh the risks associated with the treatment.

Levothyrox® New and Old Formulations: Are they Switchable for Millions of Patients?

In France, more than 2.5 million patients are currently treated with levothyroxine, mainly as the marketed product Levothyrox^®. In March 2017, at the request of French authorities, a new formulation of Levothyrox^® was licensed, with the objective of avoiding stability deficiencies of the old formulation. Before launching this new formulation, an average bioequivalence trial, based on European Union recommended guidelines, was performed. The implicit rationale was the assumption that the two products, being bioequivalent, would also be switchable, allowing substitution of the new for the old formulation, thus avoiding the need for individual calibration of the dosage regimen of thyroxine, using the thyroid-stimulating hormone level as the endpoint, as required for a new patient on initiating treatment. Despite the fact that both formulations were shown to be bioequivalent, adverse drug reactions were reported in several thousands of patients after taking the new formulation. In this opinion paper, we report that more than 50% of healthy volunteers enrolled in a successful regulatory average bioequivalence trial were actually outside the a priori bioequivalence range. Therefore, we question the ability of an average bioequivalence trial to guarantee the switchability within patients of the new and old levothyroxine formulations. We further propose an analysis of this problem using the conceptual framework of individual bioequivalence. This involves investigating the bioavailability of the two formulations within a subject, by comparing not only the population means (as established by average bioequivalence) but also by assessing two variance terms, namely the within-subject variance and the variance estimating subject-by-formulation interaction. A higher within individual variability for the new formulation would lead to reconsideration of the appropriateness of the new formulation. Alternatively, a possible subject-by-formulation interaction would allow a judgement on the ability, or not, of doctors to manage patients effectively during transition from the old to the new formulation.

Impact of a Forced Dose-Equivalent Levothyroxine Brand Switch on Plasma Thyrotropin: A Cohort Study

Background: Patients with primary hypothyroidism are treated with levothyroxine (LT4) to normalize their serum thyrotropin (TSH). Finding the optimal dosage is a long-lasting process, and a small change can have major impact. Currently, limited data are available on the impact of dose-equivalent substitution between brands. This study aimed to determine the effect of the shortage of the LT4 brand Thyrax^® in the Netherlands and the resulting dose-equivalent switch to another brand on plasma TSH concentrations in a large cohort of patients. Methods: Observational cohort study. Two registries representative for the Dutch population containing prescription and laboratory test data: the Nivel Primary Care Database and the PHARMO Database Network. Patients using at least 25 μg Thyrax daily for one year or longer were included. Two cohorts were formed: a switch cohort consisting of patients who switched from Thyrax to an alternative brand, and a Thyrax cohort including patients who continued to use Thyrax. Patients in the switch cohort did switch from Thyrax to a different brand of LT4 in 2016 and had two consecutive TSH measurements on the same dose of LT4, one before and one 6 weeks after the switch. Patients in the Thyrax cohort had two consecutive TSH measurements on the same dose of Thyrax that were 6 weeks apart. Results: In the Thyrax cohort, 19% of euthyroid patients using ≤100 μg had a TSH level outside the reference range at the subsequent measurement compared with 24% in the switch cohort (p < 0.0001). For patients using >100 μg Thyrax, these figures were 24% and 63%, respectively (p < 0.0001). Furthermore, patients using >50 μg Thyrax were four to five times more likely to become hyperthyroid after a dose-equivalent switch to a different brand compared with patients who stayed on Thyrax. Conclusions: In euthyroid patients continuing the LT4 product Thyrax at the same dose, TSH was out of range in 19-24% at least 6 weeks later. A dose-equivalent switch from Thyrax to other LT4 brands induced biochemical signs of overdosing in an even larger proportion (24-63%) of patients. The results indicate that a dose-equivalent LT4 brand switch may necessitate a dose adjustment in a large number of patients.

Levothyroxine Formulations: Pharmacological and Clinical Implications of Generic Substitution

Oral levothyroxine (LT4) is the standard therapy for patients with hypothyroidism. Oral LT4 is available in several formulations, including tablets, soft gel capsules and oral solution. Multiple brand-name and generic LT4 tablets are available. In the US, the Food and Drug Administration (FDA) has developed a protocol for establishing bioequivalence of LT4 formulations based on serum thyroxine (T4) levels after a single oral dose administered to healthy volunteers. This protocol has been criticized by professional endocrinology associations for using healthy individuals and ignoring serum thyroid-stimulating hormone (TSH) levels. In addition, the protocol did not initially correct for baseline T4 levels, although this was changed in a later version. There are concerns that the FDA's protocol could allow products with clinically significant differences in bioavailability to be declared therapeutically equivalent and interchangeable. Once a generic LT4 has been shown to be bioequivalent to a brand-name LT4, it may be substituted for that brand-name LT4 with no need for dose adjustment or follow-up therapeutic monitoring. Often, the substitution is made by the pharmacy without the physician's knowledge. Even small differences between LT4 formulations can cause significant changes in TSH levels. This may be a particular concern in vulnerable populations, including elderly, pregnant, and pediatric patients. Problems that can be encountered when switching between formulations or when original products are reformulated are discussed in this review. These problems include altered efficacy and adverse events, some of which can be caused by excipients. Patients should be maintained on the same LT4 preparation if possible. If the LT4 preparation is changed, TSH levels should be evaluated and, if necessary, the dose of LT4 adjusted.Funding: Merck.Plain Language Summary: Plain language summary available for this article.

Therapeutic challenges in the application of serum thyroid stimulating hormone testing in the management of patients with hypothyroidism on replacement thyroid hormone therapy: a review

Normalizing serum thyroid stimulating hormone (TSH) levels by lifelong treatment with levothyroxine (LT4) remains the primary goal of therapy for patients with hypothyroidism. The reference ranges for TSH are derived from populations with (supposedly) normal thyroid function. But, TSH results are affected by a number of factors including alterations in TSH levels with age, concurrent illnesses, circadian rhythm, inter- and intra-assay differences, and some commonly used medications that interfere with thyroid function or the TSH test. Furthermore, some patients are complex to manage and bringing serum TSH to within its reference range does not always resolve their symptoms of hypothyroidism. Furthermore, changes in TSH within the reference range may provoke symptoms in some sensitive patients, and others may have a personal "set point" for thyroid hormone levels that represents normal function for that individual, but which is outside the population reference range. The introduction of updated LT4 formulations, with better dosing accuracy and stability compared with older versions, should, in theory at least, provide better stability and accuracy of dosing over time. However, the new LT4 formulations are associated with manifold increases in the number of self-reported adverse events. Therefore, patients with hypothyroidism as well as the clinicians managing them need to better understand the utility as well as the limitations of the widely used TSH measurement. In addition, both pharmaceutical companies and the prescribing clinician need to take greater care when patients are switched from older to newer formulations.

Spontaneous adverse event notifications by patients subsequent to the marketing of a new formulation of Levothyrox® amidst a drug media crisis: atypical profile as compared with other drugs

Since patients may report spontaneously adverse events associated with their medications, such notifications are constantly on the rise. In 2017, an unexpected rise of notifications associated with the marketing of a new formula of Levothyrox, differing from the 30-year-old drug only by minor elements, occurred in France amidst widespread media coverage. Not much, if any, scientific or pharmacological rationale was identified to explain that signal. This led us to focus on the profile and the clinical characteristics of these notifications and compare them to those associated with other drugs. We gathered all the spontaneous drug adverse event notifications associated with either Levothyrox^® or other drugs, that we received from patients in 2017, in the sanitary territory of ~2.3 M people we surveyed. Each notification was assessed by a multidisciplinary team. We compared the number of notifications, the number of symptoms described and their clinical characteristics. A total of 1 544 patient notifications were evaluated: 1 372 cases totaling 7 342 adverse events concerned Levothyrox^® new formula, as compared with 172 cases reporting 528 adverse events for all other drugs. The number of symptoms reported per notification was significantly higher for Levothyrox^® (5.4) than for other drugs (3.1, P < 0.001). Symptoms associated with Levothyrox^® belonged to more System Organ Classes and were often unrelated to the disease or treatment, as compared with those associated with other drugs. The distribution of the cases according to the number of symptoms described was starkly different, the Levothyrox^® distribution being unimodal. Health authorities must address this issue as such large atypical reporting disproportionally affects the European pharmacovigilance database.

A new formulation of levothyroxine engineered to meet new specification standards

Background: Small variations in the dose of levothyroxine have been associated with marked variations in thyroid function in people with hypothyroidism. Accordingly, regulators have identified levothyroxine as a "narrow therapeutic index" drug subject to more stringent regulations compared with other drugs, in terms of the accuracy and stability of the amount of active drug in each tablet (typically required to be 95-105% of the labelled amount over its full shelf life), and its bioavailability geometric mean ratios (90% confidence intervals between 90-111.1%, including 100%).Review: This review describes a reformulation of a widely used levothyroxine product (Euthyrox.*). The new tablet fulfils all criteria according to the new specification regulations for dosage accuracy over a shelf life of 3 years in all climate zones, and for bioequivalence compared to the conventional formulation used for many years. In addition, a clinical trial demonstrated equivalent exposure between three different tablet strengths of the new formulation, amounting to the same total dose (dose form proportionality). As a consequence, switching from the conventional to the new formulation can be undertaken on a 1:1 dose-for-dose basis, without re-titration or additional thyroid function testing.Conclusion: The new formulation, which is more stable, will assist in the accurate dosage and titration of levothyroxine in the management of hypothyroidism.

Identification of Primary Medication Concerns Regarding Thyroid Hormone Replacement Therapy From Online Patient Medication Reviews: Text Mining of Social Network Data

BACKGROUND

Patients with hypothyroidism report poor health-related quality of life despite having undergone thyroid hormone replacement therapy (THRT). Understanding patient concerns regarding levothyroxine can help improve the treatment outcomes of THRT.

OBJECTIVE

This study aimed to (1) identify the distinctive themes in patient concerns regarding THRT, (2) determine whether patients have unique primary medication concerns specific to their demographics, and (3) determine the predictability of primary medication concerns on patient treatment satisfaction.

METHODS

We collected patient reviews from WebMD in the United States (1037 reviews about generic levothyroxine and 1075 reviews about the brand version) posted between September 1, 2007, and January 30, 2017. We used natural language processing to identify the themes of medication concerns. Multiple regression analyses were conducted in order to examine the predictability of the primary medication concerns on patient treatment satisfaction.

RESULTS

Natural language processing of the patient reviews of levothyroxine posted on a social networking site produced 6 distinctive themes of patient medication concerns related to levothyroxine treatment: how to take the drug, treatment initiation, dose adjustment, symptoms of pain, generic substitutability, and appearance. Patients had different primary medication concerns unique to their gender, age, and treatment duration. Furthermore, treatment satisfaction on levothyroxine depended on what primary medication concerns the patient had.

CONCLUSIONS

Natural language processing of text content available on social media could identify different themes of patient medication concerns that can be validated in future studies to inform the design of tailored medication counseling for improved patient treatment satisfaction.

European Thyroid Association (ETA) and Thyroid Federation International (TFI) Joint Position Statement on the Interchangeability of Levothyroxine Products in EU Countries

Several European countries have seen major health issues after a switch from one levothyroxine brand to another, as well as following the introduction of several levothyroxine formulation changes. While the relationship between these health issues and brand or formulation changes merits further investigation, the current position statement on behalf of both health-care providers and patients summarizes recent events in several European countries and provides a number of recommendations to limit the burden for patients, so as to prevent increased health-care consumption and health-care expenses in this context.