The recommended treatment for latent tuberculosis infection for adults is a daily dose of isoniazid 300mg during 6 months. In Brazil, isoniazid was formulated as 100 mg tables. The treatment duration and the high pill burden compromised patient adherence to the treatment. The Brazilian National Programme for Tuberculosis requested the development of a new 300mg isoniazid formulation. The aim of the study is to compare the bioavailability of the isoniazid 300mg new formulation and three 100mg tablets of the reference formulation.