Distribution of exposure characteristics of conventional NSAIDs and coxibs and RRs of upper GI events during current exposure (compared to past exposure).

Each NSAID prescription was classified according to first-ever use, long gap (previous prescription at least 6 mo before), and short gap (previous prescription within the last 6 mo). The medication possession ratio was estimated for the prescriptions issued after a short gap and divided into very low (<0.40), low (0.40–0.59), moderate (0.60–0.79), and high (0.80+). Short-term use was defined ≤4 prescriptions in the 1 y before, medium-term 5–11, and long-term ≥11 prior NSAID prescriptions. Rx, prescription.