Bioequivalence of Two Levothyroxine Tablet Formulations in Healthy Indian Volunteers

GSK markets a drug called levothyroxine or T4 that is used to treat patients with hypothyroidism. Till date, the active drug substance or active pharmaceutical ingredient (API) for levothyroxine tablets marketed in India has been obtained from a particular source. GSK India proposes to change the source of the API from the existing source to a new source. Some patients may experience a change in clinical effect when switched from one formulation to another. Therefore this study is being done to understand whether a change in API in levothyroxine tablet has any impact on the clinical effect of the drug. The purpose of this study is to: See how quickly the levothyroxine tablet from the new source (single dose of 600mcg) enters the bloodstream, is distributed in the body, broken down and removed compared to the levothyroxine tablet from the existing source (single dose of 600mcg). Study the effect of single 600mcg doses of levothyroxine tablet from new source and levothyroxine tablet from existing source on TSH level in the blood. Study the safety and side effects of single 600mcg doses of levothyroxine tablet from new source and levothyroxine tablet from existing source.