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Table 1 Levels of evidence used to justify post-marketing withdrawal of medicinal products

From: Post-marketing withdrawal of 462 medicinal products because of adverse drug reactions: a systematic review of the world literature

Level of evidencea Number (%) of withdrawals
All marketed drugs (n = 462) Marketed drugs launched since 1950 (n = 286)
Level 1: Systematic reviews 6 (1.3) 6 (2.1)
Level 2: Randomized studies 27 (5.8) 25 (8.7)
Level 3: Non-randomized studies 43 (9.3) 30 (10.5)
Level 4: Case reports 330 (71.4) 189 (66.1)
Level 5: Mechanism-based reasoning 56 (12.1) 36 (12.6)
  1. aBased on the Oxford Centre for Evidence-Based Medicine Levels of Evidence [13]. Level 1, Systematic review of randomized trials, systematic review of nested case-control studies; Level 2, Individual randomized trial or (exceptionally) observational study with dramatic effect; Level 3, Non-randomized controlled cohort/follow-up study (post-marketing surveillance); Level 4, Case-series, case-control, or historically controlled studies; Level 5, Mechanism-based reasoning