Liquid and softgel levothyroxine use in clinical practice: state of the art

Levothyroxine is recognized as the treatment of choice for hypothyroidism. So far, the tablet levothyroxine has been the formulation almost exclusively used, even though an optimal daily dose of levothyroxine has been unsuccessfully sought and a consensus not achieved. Due to progressive use of a more individually tailored levothyroxine dose, increasing evidence has instead displayed that many gastrointestinal disorders, polypharmacy, and food interference may raise the daily levothyroxine requirement. In recent years, alternative levothyroxine formulations have become available and have rapidly gained attention because of their pharmacokinetic properties. This study aims to provide an overview regarding the use of softgel capsule and/or liquid levothyroxine solution while performing a review of published studies about such topic. A comprehensive computer literature search of the PubMed/MEDLINE, Scopus, and Google Scholar databases has been conducted to find published articles on this topic. The search algorithm was based on the combinations of the following terms: "oral solution" or "soft gel" or "liquid", and "levothyroxine". The computer search resulted in 75 articles; through a critical review of such titles and abstracts and a screening of their references lists, the review included 18 original articles relating to 800 patients treated with alternative formulations. Despite some limits, the results obtained using softgel and liquid levothyroxine were consistent with each other. In selected categories of levothyroxine-treated patients (pediatric, suffering from hypo-achlorhydria, polypharmacy, undergone bariatric surgery, fed through enteric tube) these new formulations have shown promising attributes in improving a treatment that needs to be individually tailored.