************ Introduction ************ This document is meant to be read by a person willing to write a new Tucuxi drug model. We first start with the raw description of the minimal required information that should be found in a population PK model, chapter :ref:`model_selection`. Then, in :ref:`drugmodel_writing`, we describe how the drug model should be filled. Finally we present several ways to validate your drug model in :ref:`drugmodel_validation`. Another chapter, :ref:`pkmodels`, is dedicated to the description of the available PK models.