Upper gastrointestinal bleeding associated with NSAIDs, other drugs and interactions: a nested case-control study in a new general practice database. 
To test the ability a new Spanish primary care research database (BIFAP) to capture the association between upper gastrointestinal bleeding (UGIB) and NSAIDs and other drugs and compare the results with previous studies.  We performed a nested case-control study in persons aged 40-90 years old included in the period 2001-2005.  Potential cases were selected through a computer search followed by an individual blinded review.  Controls matched for age, sex and calendar year were randomly selected.  The exposure window was defined as 0-30 days before the index date.  Adjusted odds ratios were obtained through unconditional logistic regression models.  In a study cohort of 669,115 subjects (1,576,442 person-years) we retrieved 1,193 valid incident cases.  Increased risks were found with current use of NSAIDs (RR = 1.72; 95 %CI: 1.41-2.09), metamizole (1.52; 1.09-2.13), low-dose aspirin (1.74; 1.37-2.21), other antiplatelet drugs (1.73; 1.27-2.36), and oral anticoagulants (2.00; 1.44-2.77).  We did not find an increased risk with current use of oral corticosteroids (1.11; 0.66-1.86), SSRIs (1.05; 0.77-1.42), or paracetamol (1.00; 0.82-1.23).  Acid-suppressing drugs reduced the risk among users of NSAIDs (0.58; 0.39-0.85), particularly in users with antecedents of peptic ulcer (0.16; 0.05-0.58).  We detected a decreasing time-trend in the relative risk and the population attributable proportion associated with NSAIDs over the study period.  The increased risk of UGIB associated with NSAIDs was lower than previously reported, which could partly be explained by methodological differences, but a decreasing burden over time of this drug safety problem is suggested.  BIFAP has shown to be a valuable tool for pharmacoepidemiological research.