Newer Oral Levothyroxine Formulations: Is It Time to Switch Over?

Abstract

Primary hypothyroidism is a frequent presentation in primary care, and is treated with levothyroxine sodium tablets once daily in the morning in the fasting state. With an adequate dose, the goal is to achieve a thyroid stimulating hormone in the normal range in 6–8 weeks. Medications, foods, and gastrointestinal conditions can interfere with the absorption of the levothyroxine tablet. This can lead to increased visits to the laboratory and physician, necessitating frequent dosage changes, and causing suboptimal care. The newly-introduced oral solutions and soft gel capsule formulations received approval for use by regulatory authorities. This article describes the kinetics of levothyroxine, examines the available evidence from the literature, and summarises the rightful place of the levothyroxine solution from the perspective of the clinical practitioner. At the end of the analysis, it is evident that more robust trials with this new formulation are needed to consider a switchover from tablet form for millions of patients, in order to justify the cost. The newer levothyroxine formulations may have a role in selected patients with resistant hypothyroidism.