Venous thromboembolism (VTE) which includes pulmonary embolism (PE), or deep venous thrombosis (DVT) poses an important disease burden, however, much remains unknown about the risk factors that cause it. In recent years, more attention has focused on medications that play a role in the development of drug-induced venous thrombosis. The three studies in this dissertation explore the risk of VTE in relation to the use of specific pharmacologic agents; glucocorticoids, 5ARIs and statins in three distinct patient populations with; asthma, benign prostatic hyperplasia (BPH) and hypercholesterolemia, using different approaches to address the inevitable confounding present in etiologic pharmacoepidemiologic research. Using a nested case-control design for the first two studies and cohort design for the last, we assessed the risk of VTE in relation to timing of drug exposure, duration of use, number, and dose of prescriptions. The base populations comprised subjects who received at least one prescription for any of the pharmacologic agents of interest (during 1995–2015 for study 1 and 2 and 1995–2018 for study 3) in the UK-based Clinical Practice Research Datalink. We used descriptive analyses as well as conditional logistic regression and Poisson regression models to evaluate the relationship between these drugs and the risk of VTE. Study 1 examined the relationship between glucocorticoid use and venous thromboembolism among asthma patients age 20–59. We found that current and systemic glucocorticoid use was associated with an increased risk of VTE, with a dose-response relationship. Study 2 explored the relationship between VTE and 5ARI use compared to alpha blocker use among patients, age 40–79, with BPH. We observed that cumulatively high doses of 5ARI+/-AB increases the risk of incident VTE. In study 3, we examined the relationship between VTE and statin use compared to fibrate use among 40–79-year-old patients with hypercholesterolemia. We observed that statin use decreases the risk of incident VTE. These three studies in a large population-based database of high quality, efficiently evaluate the safety/unintended benefit of glucocorticoids, 5ARIS and statins, with the hope to guide the development of guidelines for their use in prolonged care of asthma, BPH and hypercholesterolemia, respectively. / 2023-08-25T00:00:00Z