Study of Dose Adjustment From Levothyroxine to a New Levothyroxine Sodium Test Formulation

The drug being tested in this study is a new sodium formulation of levothyroxine. Levothyroxine (L-Thyroxine Christiaens®) is used in the treatment of hypothyroidism. This study will investigate the effect of switching subjects taking levothyroxine to a new levothyroxine sodium formulation.

The results of this study will be used to provide instructions to general practitioners and endocrinologists assisting patients on levothyroxine hormone substitution in performing the switch to the new formulation.

The study will enroll approximately 90 patients. Patients receiving the same daily dose of L-Thyroxine Christiaens® during the past 6 weeks and with serum thyroid stimulating hormone (TSH) levels between 0.4-2.5 mU/L will be switched to the equivalent daily dose of the new formulation of levothyroxine. After the switch, patients will be followed up after 2 (± 2 weeks) and 4 months (± 4 weeks).

All participants will be asked to take a daily dose at the same time each day throughout the study.

This study will be conducted in Belgium. Participants will make 3 to 4 visits to the clinic.

Inclusion criteria

• (Near) total thyroidectomised patients.
• Aged 18 years and older.
• Stabilised on the same daily dose of L-Thyroxine Christiaens® during the last 6 weeks before inclusion in the study.
• Written informed consent given.
• Able and willing to comply with protocol requirements and to complete the study.

Exclusion criteria

• History of Graves' disease or positive TSH-receptor antibodies.
• History of thyroid cancer requiring TSH suppression.
• Medical procedures or treatments planned that could influence the thyroid hormone state of the patients during this trial.
• Use of levothyroxine containing medicines provided by other brands to treat hypothyroidism.
• Pregnant or planning pregnancy. Female patients of childbearing potential need to apply highly effective methods of birth control.
• Participation in another trial in the past 6 weeks.
• Exclusion criteria during the study are the occurrence of any serious adverse reaction, any laboratory or clinically relevant change in patient status, any change in smoking status, use of drugs non-authorized by the physician (to avoid relevant drug interactions) and lack of patient compliance with the study drug. (OR events not considered as exclusion criteria but to be documented in the case report form, as a possible explanation for change in lab parameters and/or dose switch).