ObjectivesThis study investigates the relationship between current morphine use and the risk of pulmonary embolism (PE) development in deep vein thrombosis (DVT) patients.MethodsWe conducted a population-based nested case-control retrospective analysis using the Longitudinal Health Insurance Database 2000 of Taiwan. A DVT cohort of 3668 patients with no history of PE from 1998 to 2010 and the other cohort of 174 patients who subsequently developed PE were evaluated. Morphine use was designated as current' if the prescription duration covered the index date or ended within 30 days before the index date. Logistic regression was used to estimate the odds ratios and 95% confidence intervals (CI), and the multivariable model was applied to control for age.ResultsCompared with non-morphine users, DVT patients who received morphine within 30 days of the index date had a 4.54-fold (95% CI=2.30-8.97) chance of developing PE. The risk of PE development increased with an increase in cumulative dosage and in the average dosage of morphine.ConclusionThe incidence of PE in DVT patients in Taiwan is associated with current morphine treatment (30 days) and is dependent on dosage.