Drug therapy problems (DTPs) (or drug related problems, DRPs) represent the categorization and definition of clinical problems related to the use of medications or "drugs" in the field of pharmaceutical care. In the course of clinical practice, DTPs are often identified, prevented, and/or resolved by pharmacists in the course of medication therapy management, as experts on the safety and efficacy of medications, but other healthcare professionals may also manage DTPs. A drug-therapy (related) problem can be defined as an event or circumstance involving drug treatment (pharmacotherapy) that interferes with the optimal provision of medical care. In 1990, L.M. Strand and her colleagues (based on the previous work of R.L Mikeal and D.C Brodie, published respectively in 1975 and 1980) classified the DTPs into eight different categories. According to these categories, pharmacists generated a list of the DTPs for each patient. As a result, pharmacists had a cleaner picture of the patient's drug therapy and medical conditions. A second publication of R.J Cipolle with L.M Strand in 1998, change the eight categories into seven, grouped in four Pharmacotherapy needs: indication, effectiveness, safety and adherence.