Oral liquid levothyroxine solves the problem of tablet levothyroxine malabsorption due to concomitant intake of multiple drugs.
Unlike the tablet (TAB) formulation, liquid L-T4 (LIQ) is directly absorbed in the intestine. The aim of this study was to assess whether LIQ was superior to TAB, such that it would overcome the interference induced by co-ingestion of multiple interfering drugs (ID).



In this prospective cohort study, we recruited 11 patients with apparent reduced TAB absorption due to ≥ 2 ID, and switched them to LIQ while maintaining the daily dose and the co-ingestion of the ID. Serum TSH was assayed at least twice every eight weeks.



Serum TSH was significantly lower on LIQ compared with TAB (P < 0.0001), in patients who took L-T4 for either replacement (P = 0.002) or TSH-suppression (P < 0.0001). This difference was evident already at the first measurement post-switch (P = 0.008 or P = 0.03). Regardless of the purpose of L-T4 therapy, patients who took two ID had lower serum TSH on LIQ compared with patients who took three ID (P = 0.0006). Interestingly, 2/3 patients who failed to reach target TSH levels while on LIQ took three ID.



LIQ overcomes the concurrent interference exerted by the ingestion of multiple ID. In such cases, switching from TAB to LIQ permits patients to reach target TSH within 8 weeks.
a Department of Clinical and Experimental Medicine , University of Messina , Messina , Italy.
Roberto
R
Vita
a Department of Clinical and Experimental Medicine , University of Messina , Messina , Italy.
Flavia
F
Di Bari
a Department of Clinical and Experimental Medicine , University of Messina , Messina , Italy.|b Master Program on Childhood, Adolescent and Women's Endocrine Health , University of Messina , Messina , Italy.|c Interdepartmental Program of Molecular & Clinical Endocrinology, and Women's Endocrine Health , University hospital, Policlinico Universitario G. Martino , Messina , Italy.
Salvatore
S
Benvenga
D000328:Adult; D000368:Aged; D002626:Chemistry, Pharmaceutical / Q000379:methods*; D015331:Cohort Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D013607:Tablets; D013974:Thyroxine / Q000008:administration & dosage* / Q000493:pharmacokinetics
D013607:Tablets; D013974:Thyroxine
Levothyroxine; calcium; iron; proton-pump inhibitors; sevelamer