[2] 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.
Strand and her colleagues (based on the previous work of R.L Mikeal[3] and D.C Brodie,[4] published respectively in 1975 and 1980) classified the DTPs into eight different categories.
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.
[5] According to page 73 in Introduction to Health Care Delivery: A Primer for Pharmacists, drug therapy problems (DTP) originated from Strand et al. (1990) who defined eight problems that could result in poorer health outcomes in an attempt to categorize DTP.
[7] Helper and Strand later in 1990 stated the mission statement or raison d'etre of pharmacists should be to correct these drug therapy problems.