Advancements in the treatment of hypothyroidism with L-T4 liquid formulation or soft gel capsule: an update

ABSTRACT

Introduction: The most recent advance concerning levothyroxine (L-T4) therapy is the development of novel oral formulations: the liquid preparation, and the soft gel capsule.

Areas covered: This review evaluates the most recent clinical studies about these new formulations. The liquid formulation has been shown to overcome: the food and beverages intereference with L-T4 tablets absorption, caused by food or coffee at breakfast; malabsorption induced by the increased gastric pH, resulting from atrophic gastritis, or due to proton-pump inhibitors; and malabsorption after bariatric surgery. The use of liquid L-T4 has been studied also in pregnancy, newborns and infants, suggesting a better bioequivalence than tablets. Finally, liquid L-T4 is more active than tablets in the control of thyroid-stimulating hormone (TSH) in hypothyroid patients without malabsorption, drug interference, or gastric disorders, leading to a hypothesized higher absorption of liquid L-T4 also in these patients. Few studies have evaluated soft gel L-T4 with promising results in patients with malabsorption related to coffee or gastritis.

Expert opinion: Liquid L-T4 (and soft gel capsules) are more active than the tablet L-T4 in the control of TSH in hypothyroid patients with gastric disorders, malabsorption, or drug interference, but also in patients without absorption disorders.

KEYWORDS:

• Bariatric surgery
• drug interference
• gastritis
• liquid L-T4
• L-T4
• malabsorption
• PPI
• soft gel L-T4
• tablet L-T4

Article highlights

• The most recent advance concerning L-T4 therapy is the development of novel oral formulations: the liquid preparation, and the soft gel capsule. The liquid formulation is composed of L-T4, glycerin and ethanol, and it does not need a gastric phase of dissolution.

• The most important advantage of the liquid L-T4 solution is the possibility of administration in patients who are not able to swallow tablets, such as in patients treated through enteral feeding tube.

• The liquid formulation has been shown to overcome: 1 – the food and beverages intereference with L-T4 tablets absorption, caused by food or coffee at breakfast; 2 – malabsorption induced by the increased gastric pH, resulting from atrophic gastritis, or due to PPI therapy; 3 – malabsorption in patients with BPD, or RYGB after bariatric surgery.

• Moreover, the use of L-T4 as liquid solution has been studied also in pregnancy, newborns and infants, suggesting a better bioequivalence than L-T4 in tablets.

• Finally, it has been shown that liquid L-T4 is more effective than L-T4 tablet in controlling TSH levels in hypothyroid patients without malabsorption, gastric disorders, or drug interference, suggesting an increased absorption of L-T4 with the liquid formulation also in these patients.

• Few studies have evaluated soft gel L-T4 in clinical studies with promising results in patients with malabsorption related to coffee or gastritis.

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Declaration of interest

The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.

Additional information

Funding

This paper was not funded.