Introduction: The main pharmacovigilance system in the United Kingdom is the ‘Yellow Card’ spontaneous reporting system which suffers from low reporting rate, and long lag time between drug launch and ADR recognition. Aim: The aim of this study is to develop a pharmacovigilance system to permit the early detection of adverse drug reactions using routinely acquired NHS health data with minimal cost and resources. Methods: There are 2 methods for this study; Phase 1: The extraction of drug persistence data from routinely acquired NHS health data, and Phase 2: Identifying the exact reason(s) for patient discontinuation of drug therapy within 6 months of the index prescription. Results: Phase1: During the study period 4243 patients were initiated on ramipril, 8849 patients on simvastatin, 3242 patients on ARBs, 3646 patients on amlodipine and 269 patients on lercanidipine. The 1, 2-3 and 4-6 month discontinuation rates were 9.9%, 4.9% and 4.2% respectively for ramipril, 9.5%, 3.4% and 3.2% for simvastatin, 8.7%, 2.9% and 2.5% for ARBs, 16.2%, 6.3% and 4.8% for amlodipine, and 17.8%, 3.7% and 3.7% for lercanidipine. Drug discontinuation rates determined agree closely with published data from trials and post marketing surveys in terms of the peak time at which ADRs and discontinuations occur (1 month), the populations most frequently affected (females and the young or elderly depending on drug), and the relationship between the frequency of ADRs and discontinuations relative to the drug of interest, especially for antihypertensive (CCBs>ACEIs>ARBs). Phase 2: Six (20%) of 30 participating primary care practices, contributing to the PTI database, agreed to be approached directly. Completed data was returned for 98% of patients whom discontinued amlodipine due to a specific ADR. Conclusions: Drug discontinuation rates obtained from health care databases is a good surrogate for ADR/E rates. Specific reasons for discontinuation, such as adverse drug reactions, can be identified directly from such electronic databases or more effectively from the primary care medical records held in primary care practices.