Is it worth improving the effectiveness of a treatment by modulating the prescription schedule? Data show that the preferred administration timing depends on biological rhythms. Taking this into consideration can improve efficiency or reduce side effects. Food also plays a role. However, for most medications, setting a schedule that is too strict in relation to meals may not be clinically relevant and can lead to « therapeutic weariness ». To ensure effectiveness, tolerance and economy of a treatment, it is more important to ask patients about their habits and to define with them the best schedule.