Orthodontic therapy is based on the continuous application of forces to the tooth which lead to the remodelling of the alveolar bone and result in the displacement of the tooth. There are several theories of displacement and the general principle is that the force acting on the tooth crown is transmitted via the root to the periodontal ligament (PDL) and alveolar bone, where resorption at the pressure site and deposition of new bone at the site of the application of the force will occur. However, not all patients have been shown to respond equally to therapy. In some cases, there is a reduction or absence of displacement, while in some situations the movement of the tooth takes place faster than expected. Numerous studies have shown that a range of biological and chemical factors, that can be affected by drugs and pharmacological preparations, also influence the process of alveolar bone remodelling. Thus, for example, drugs from the nonsteroidal anti-inflammatory drugs (NSAID) group can lead to a decrease in the rate of tooth movement, while drugs from the corticosteroid group affect faster bone resorption and lead to faster movement. Since orthodontic therapy is performed in almost all age groups, it is important to keep in mind that patients could be taking a variety of pharmacological preparations to prevent or treat an existing disease which can potentially affect the speed and success of the orthodontic tooth movement. Therefore, it is important to constantly expand the knowledge and consider how each drug or pharmacological preparation can potentially affect the outcome of therapy.