title: Switching levothyroxine from the tablet to the oral solution formulation corrects the impaired absorption of levothyroxine induced by proton-pump inhibitors.
abstract: BACKGROUND
  Proton-pump inhibitors (PPIs) impair tablet levothyroxine (LT4) intestinal absorption by increasing the gastric pH and decreasing LT4 dissolution in the stomach.
  
  
  OBJECTIVE
  The purpose of this study was to verify whether a liquid formulation of LT4 would correct LT4 malabsorption induced by PPIs.
  
  
  METHODS
  This was a prospective observational cohort study. The study was conducted from 2012 to 2013, and the mean duration of the follow-up was 23.7 ± 11.9 weeks.
  
  
  METHODS
  The study was conducted in a tertiary university hospital outpatients clinic.
  
  
  METHODS
  Upon informed consent, we recruited 24 consecutive adult patients (18 women and 6 men), who took LT4 for replacement (n = 14) or suppressive purposes (n = 10) and who had absorption of tablet LT4 impaired by PPIs.
  
  
  METHODS
  The 24 patients were switched from the tablet to the oral solution LT4 at the same daily dose.
  
  
  METHODS
  Significantly lower mean TSH levels were seen with the oral solution than with the tablet as were significantly greater rates of serum TSH less than or equal to the specified cutoff values (replacement [REP] group) or ≤ 0.10 mU/L (suppressive [SUP] group) with the oral solution than with the tablet.
  
  
  RESULTS
  Serum TSH was lower with the oral solution than with the tablet formulation (REP group, 1.7 ± 1.0 mU/L vs 5.4 ± 4.3, P < .0001; SUP group, 0.1 ± 0.3 mU/L vs 2.1 ± 2.7, P < .0001). In the REP group, the rate of TSH values of ≤ 4.12 or ≤ 2.5 mU/L was 29 of 30 (96.7%) or 24 of 30 (80.0%) postswitch but only 17 of 36 (47.2%) or 9 of 36 (25.0%) preswitch (P < .0001). In the SUP group, the rate of serum TSH values of ≤ 0.10 mU/L was 26 of 35 (74.3%) postswitch but 0 of 22 (0%) preswitch (P < .0001).
  
  
  CONCLUSIONS
  These data demonstrate the continued absorption of liquid LT4 despite the increased gastric pH due to PPI therapy.
authors.affiliation: Endocrinology (R.V., G.S., F.T., S.B.), Department of Clinical and Experimental Medicine University of Messina, 98125 Messina, Italy; Master Program on Childhood, Adolescence and Women's Endocrine Health (S.B.), University of Messina, 98125 Messina, Italy; and Interdepartmental Program of Molecular and Clinical Endocrinology and Women's Endocrine Health (S.B.), A.O.U. Policlinico G. Martino, 98125 Messina, Italy.
authors.forename: Roberto
authors.initials: R
authors.lastname: Vita
authors.forename: Giovanna
authors.initials: G
authors.lastname: Saraceno
authors.forename: Francesco
authors.initials: F
authors.lastname: Trimarchi
authors.forename: Salvatore
authors.initials: S
authors.lastname: Benvenga
mesh_terms: D000328:Adult; D000368:Aged; D015331:Cohort Studies; D004347:Drug Interactions; D005260:Female; D006801:Humans; D007408:Intestinal Absorption / Q000187:drug effects*; D008297:Male; D008875:Middle Aged; D019999:Pharmaceutical Solutions; D011446:Prospective Studies; D054328:Proton Pump Inhibitors / Q000009:adverse effects*; D013607:Tablets; D013972:Thyrotropin / Q000097:blood; D013974:Thyroxine / Q000008:administration & dosage* / Q000493:pharmacokinetics
chemical_list: D019999:Pharmaceutical Solutions; D054328:Proton Pump Inhibitors; D013607:Tablets; D013972:Thyrotropin; D013974:Thyroxine