title: The administration of L-thyroxine as soft gel capsule or liquid solution.
abstract: BACKGROUND
  Levothyroxine (l-T4) is the mainstay of treating hypothyroidism. The tablet is the traditional formulation of l-T4. Tablet l-T4 malabsorption results from either hindered gastric dissolution of the tablet or binding of l-T4 by sequestrants in the intestinal lumen.
  
  
  METHODS
  This review provides an overview of the pharmacokinetics of l-T4 formulations available in the market: the tablet, the soft gel capsule and the oral solution. We review literature on the new formulations and anticipate the areas of future research.
  
  
  CONCLUSIONS
  Failure of l-T4 treatment to reach target serum thyroid-stimulating hormone levels generally prompts the physicians to increase l-T4 daily dose. In vitro studies have shown that the soft gel capsule releases the active ingredient more consistently at varying pH than the tablet. In addition, in vivo studies have confirmed the in vitro data and have demonstrated that both the soft gel capsule and the liquid formulation are capable to solve tablet l-T4 malabsorption caused by certain drugs, bariatric surgery or coffee. These new formulations may be attractive also for patients who cannot/do not want to change their (improper) habits of l-T4 ingestion. Finally, the oral solution l-T4 could be suitable for patients who cannot swallow the solid formulations.
authors.affiliation: University of Messina, Endocrinology, Department of Clinical & Experimental Medicine , Viale Gazzi, Padiglione H, 4 piano, 98125 Messina , Italy +39 090 221 3560 ; +39 090 221 3518 ; roberto.vita@yahoo.it.
authors.forename: Roberto
authors.initials: R
authors.lastname: Vita
authors.forename: Poupak
authors.initials: P
authors.lastname: Fallahi
authors.forename: Alessandro
authors.initials: A
authors.lastname: Antonelli
authors.forename: Salvatore
authors.initials: S
authors.lastname: Benvenga
mesh_terms: D000284:Administration, Oral; D000818:Animals; D002214:Capsules; D002626:Chemistry, Pharmaceutical; D004337:Drug Carriers; D005782:Gels; D006801:Humans; D007408:Intestinal Absorption; D019999:Pharmaceutical Solutions; D013607:Tablets; D013974:Thyroxine / Q000008:administration & dosage* / Q000493:pharmacokinetics
chemical_list: D002214:Capsules; D004337:Drug Carriers; D005782:Gels; D019999:Pharmaceutical Solutions; D013607:Tablets; D013974:Thyroxine
keywords: drugs; intestinal absorption; levothyroxine; oral solution; soft gel capsule