Drug switching is a common medical practice. It indicates continuation of treatment regardless of the reason why the original therapy was stopped and switched. Therefore, the aims of this study were to develop a novel method for determining drug switching from routinely acquired NHS health data and to explore the aspect of continuation of care for patients. Patients who were first prescribed ramipril, simvastatin and an angiotensin receptor blocker (ARB) between 1 March 2004 and 28 February 2007 and discontinued their medication within 6 months of the index prescription were identified from the PTI database. The identified patients were then categorized into three groups: i) patients who were switched to a different drug for the same medical condition, ii) patients who were being prescribed with other types of antihypertensive/lipid-regulating drug prior to the initiation of study; and iii) patients who were without any continuation of care or therapy. Twenty percent (808), 29%(1429) and 14%(455) of the identified patients discontinued ramipril, simvastatin and ARB, respectively, within 6 months of an index prescription. Among the ramipril discontinuation group, 36.4% of the patients were switched to another antihypertensive, while another 31.6% of them were without continuation of care. In patients discontinuing ARB, 30.6% were switched, while another 30.1% were without continuation of treatment. In patients discontinuing simvastatin, 28.8% were switched to another lipid-regulating medicine, while another 63.1% of them were without continuation of care. The results of this study confirm that primary care prescribing databases can be used to determine drug-switching information and continuation of care/therapy.