Stability and Compatibility Studies of Levothyroxine Sodium in Solid Binary Systems-Instrumental Screening

Host-Guest Complexation of Olmesartan Medoxomil by Heptakis(2,6-di-O-methyl)-β-cyclodextrin: Compatibility Study with Excipients

Background: Olmesartan medoxomil (OLM) is the prodrug of olmesartan, an angiotensin II type 1 receptor blocker that has antihypertensive and antioxidant activities and renal protective properties. It exhibits low water solubility, which leads to poor bioavailability and limits its clinical potential. To improve the solubility of OLM, a host-guest inclusion complex (IC) between heptakis(2,6-di-O-methyl)-β-cyclodextrin (DMβCD) and the drug substance was obtained. Along with active substances, excipients play a crucial role in the quality, safety, and efficacy of pharmaceutical formulations. Therefore, the compatibility of OLM/DMβCD IC with several pharmaceutical excipients was evaluated. Methods: IC was characterized in both solid and liquid states, employing thermoanalytical techniques, universal-attenuated total reflectance Fourier-transform infrared spectroscopy, powder X-ray diffractometry, UV spectroscopy, and saturation solubility studies. Compatibility studies were carried out using thermal and spectroscopic methods to assess potential physical and chemical interactions. Results: The 1:1 OLM:DMβCD stoichiometry ratio and the value of the apparent stability constant were determined by means of the phase solubility method that revealed an AL-type diagram. The binary system showed different physicochemical characteristics from those of the parent entities, supporting IC formation. The geometry of the IC was thoroughly investigated using molecular modeling. Compatibility studies revealed a lack of interaction between the IC and all studied excipients at ambient conditions and the thermally induced incompatibility of IC with magnesium stearate and α-lactose monohydrate. Conclusions: The results of this study emphasize that OLM/DMβCD IC stands out as a valuable candidate for future research in the development of new pharmaceutical formulations, in which precautions should be considered in choosing magnesium stearate and α-lactose monohydrate as excipients if the manufacture stage requires temperatures above 100 °C.

Advancing drug safety and mitigating health concerns: High-resolution mass spectrometry in the levothyroxine case study

Levothyroxine is a drug with a narrow therapeutic index. Changing the drug formulation composition or switching between pharmaceutical brands can alter the bioavailability, which can result in major health problems. However, the increased adverse drug reactions have not been fully explained scientifically yet and a thorough investigation of the formulations is needed. In this study, we used a non-targeted analytical approach to examine the various levothyroxine formulations in detail and to reveal possible chemical changes. Ultra-high-performance liquid chromatography coupled with a data-independent acquisition high-resolution mass spectrometry (UHPLC-DIA-HRMS) was employed. UHPLC-DIA-HRMS allowed not only the detection of levothyroxine degradation products, but also the presence of non-expected components in the formulations. Among these, we identified compounds resulting from reactions between mannitol and other excipients, such as citric acid, stearate, and palmitate, or from reactions between an excipient and an active pharmaceutical ingredient, such as levothyroxine-lactose adduct. In addition to these compounds, undeclared phospholipids were also found in three formulations. This non-targeted approach is not common in pharmaceutical quality control analysis. Revealing the presence of unexpected compounds in drug formulations proved that the current control mechanisms do not have to cover the full complexity of pharmaceutical formulations necessarily.

Potency and Powder X-ray Diffraction (PXRD) Evaluation of Levothyroxine Sodium Tablets under Ambient, Accelerated, and Stressed Conditions

Levothyroxine tablets, although highly prescribed in the United States, have been one of the most frequently recalled products. Because of the importance of the medication, several efforts have been put in place by the United States Food and Drug Administration (US FDA) to control the quality of levothyroxine tablets available to patients using the drug. The choice of excipients used in the formulation has been shown to impact the hygroscopicity and microenvironment, and ultimately the stability of the levothyroxine tablets formulations. Based on information generated from the US FDA Enforcement Report database, one of the main reasons for recalls is the low potency of different batches of the product. The yearly product recall trends for levothyroxine formulations were determined using the FDA Enforcement Report database. Three brands of levothyroxine tablets were selected with excipient lists similar to those products that have been historically recalled. The samples were placed at ambient (~23 °C), accelerated stability (40 °C/75% RH), and stress (50 °C/75% RH) conditions for up to 6 months. Sample potencies were determined at 0, 1.5, 3, and 6 months using the methods for assay and impurities in the United States Pharmacopeia (USP) monograph for levothyroxine tablets. Additional sample monitoring was conducted by overlaying the initial powder X-ray diffractograms (PXRD) of the samples from 0 months with the patterns generated thereafter. There has been a decline in the number of levothyroxine tablets recalled over the years. The highest numbers of recalls were recorded in the years 2013 [33] and 2020 [23]; no recalls occurred in the years 2019 and 2022. All of the brands evaluated met the USP 95.0-105.0% assay requirements at 1.5 months under accelerated conditions; only one of the brands complied at 3 months. Under ambient conditions, two brands were stable at 6 months, with borderline assay results. For stability, levothyroxine was found in microgram quantities in the formulations and PXRD could not detect changes at these low levels. However, we found some distinguishing data for samples under stress conditions.

Thyroxine biosensors: a review on progress and challenges

Hypothyroidism is a global concern that needs to be monitored, controlled and treated. Thyroxine is the most common biomarker for the diagnosis of hypothyroidism and a therapeutic hormonal replacement for hypothyroid patients. People suffering from hypothyroidism need to monitor their levels of thyroxine to avoid health complications. Diagnostic labs are not always easily accessible and, hence, point-of-care biosensors can become a useful alternative. Several studies have shown high sensitivity, selectivity and stability but there is no commercial point-of-care biosensing device available. This paper presents the critical aspects, including the need for thyroxine biosensors, the physicochemical properties of the thyroxine molecule, nanomaterials and bioreceptors used for sensing. The challenges and prospects of thyroxine biosensors are also discussed.

Ionic Levothyroxine Formulations: Synthesis, Bioavailability, and Cytotoxicity Studies

Thyroid diseases affect a considerable portion of the population, with hypothyroidism being one of the most commonly reported thyroid diseases. Levothyroxine (T4) is clinically used to treat hypothyroidism and suppress thyroid stimulating hormone secretion in other thyroid diseases. In this work, an attempt to improve T4 solubility is made through the synthesis of ionic liquids (ILs) based on this drug. In this context, [Na][T4] was combined with choline [Ch]+ and 1-(2-hydroxyethyl)-3-methylimidazolium [C2OHMiM] + cations in order to prepare the desired T4-ILs. All compounds were characterized by NMR, ATR-FTIR, elemental analysis, and DSC, aiming to check their chemical structure, purities, and thermal properties. The serum, water, and PBS solubilities of the T4-ILs were compared to [Na][T4], as well as the permeability assays. It is important to note an improved adsorption capacity, in which no significant cytotoxicity was observed against L929 cells. [C2OHMiM][T4] seems to be a good alternative to the commercial levothyroxine sodium salt with promising bioavailability.

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.

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.

Levothyroxine sodium pentahydrate tablets - formulation considerations

Even though levothyroxine sodium pentahydrate tablets have been in the market since 1955, there continue to be recalls due to sub potency. We have comprehensively reviewed the factors affecting its stability in solid oral dosage forms. A compilation of marketed formulation compositions enabled the identification of the potential 'problem excipients'. Two excipient properties, hygroscopicity and microenvironmental acidity, appeared to be responsible for inducing drug instability. In drug products, depending on the formulation composition and storage conditions, the pentahydrate can dehydrate to highly reactive levothyroxine sodium monohydrate, or undergo salt disproportionation to the free acid form of the drug. The USP assay method (HPLC based) is insensitive to these different physical forms of the drug. The influence of physical form of levothyroxine on its chemical stability is incompletely understood. The USP has five product-specific dissolution tests reflecting the complexity in its evaluation.

Investigating the Influence of Excipients on the Stability of Levothyroxine Sodium Pentahydrate

A range of tablet excipients were evaluated for their influence on the physical form and chemical stability of levothyroxine sodium pentahydrate (LSP; C₁₅H₁₀I₄NNaO₄·5H₂O). LSP-excipient binary powder blends were stored under two conditions: (a) in hermetically sealed containers at 40 °C and (b) at 40 °C/75% RH. By use of synchrotron X-ray diffractometry, the disappearance of LSP could be quantified and the appearance of crystalline levothyroxine (free acid) could be identified. Under hermetically sealed conditions (40 °C) hygroscopic excipients such as povidone induced partial dehydration of LSP to form levothyroxine sodium monohydrate. When stored at 40 °C/75% RH, acidic excipients induced measurable disproportionation of LSP resulting in the formation of levothyroxine (free acid). HPLC analyses of drug-excipient mixtures revealed that lactose monohydrate, microcrystalline cellulose, and croscarmellose sodium caused pronounced chemical decomposition of LSP. On the other hand, magnesium stearate, sodium stearyl fumarate, and alkaline pH modifiers did not affect the physical and chemical stability of the API following storage at 40 °C/75% RH. HPLC, being a solution based technique, revealed chemical decomposition of the API, but the technique was insensitive to physical transformations. Excipient properties such as hygroscopicity and microenvironmental acidity were identified to be critical determinants of both physical and chemical stability of LSP in a drug product. For drugs exhibiting both physical and chemical transformations, simultaneous solid-state and solution based analyses will enable comprehensive stability evaluation.

Risperidone/Randomly Methylated β-Cyclodextrin Inclusion Complex-Compatibility Study with Pharmaceutical Excipients

Risperidone (RSP) is an atypical antipsychotic drug used in treating schizophrenia, behavioral, and psychological symptoms of dementia and irritability associated with autism. The drug substance is practically insoluble in water and exhibits high lipophilicity. It also presents incompatibilities with pharmaceutical excipients such as magnesium stearate, lactose, and cellulose microcrystalline. RSP encapsulation by randomly methylated β-cyclodextrin (RM-β-CD) was performed in order to enhance drug solubility and stability and improve its biopharmaceutical profile. The inclusion complex formation was evaluated using thermal methods, powder X-ray diffractometry (PXRD), universal-attenuated total reflectance Fourier transform infrared (UATR-FTIR), UV spectroscopy, and saturation solubility studies. The 1:1 stoichiometry ratio and the apparent stability constant of the inclusion complex were determined by means of the phase solubility method. The compatibility between the supramolecular adduct and pharmaceutical excipients starch, anhydrous lactose, magnesium stearate, and cellulose microcrystalline was studied employing thermoanalytical tools (TG-thermogravimetry/DTG-derivative thermogravimetry/HF-heat flow) and spectroscopic techniques (UATR-FTIR, PXRD). The compatibility study reveals that there are no interactions between the supramolecular adduct with starch, magnesium stearate, and cellulose microcrystalline, while incompatibility with anhydrous lactose is observed even under ambient conditions. The supramolecular adduct of RSP with RM-β-CD represents a valuable candidate for further research in developing new formulations with enhanced bioavailability and stability, and the results of this study allow a pertinent selection of three excipients that can be incorporated in solid dosage forms.